Dave Richards AA7EE

November 11, 2015

A Few Manhattan, and General, Construction Pointers

Filed under: Amateur Radio,Ham Radio,homebrew radio,QRP — AA7EE @ 9:27 pm

Someone recently left a comment on one of my older blog-posts asking if I could go into a little more detail about my construction techniques. It’s a question I’ve been asked a few times and although I have never detailed them in one post, if you were to read the posts for my main construction projects, you’d probably be able to glean enough info and links to pick up what you need. However, that information is scattered around this blog, so this post is an attempt to gather all the tidbits into one place. Please note that this is not a step-by-step “how-to” instructional, but more a collection of thoughts, tips, and links. It is a rough guide to how I do it, and not intended to be definitive. There are many ways to achieve a goal, and your mission is to find the way that works best for you.

I get my PCB material from seller acbfab on eBay. He has a good selection of different thicknesses of substrate, double-sided and single-sided, and even different thicknesses of copper. 0.06″ thickness is a nice stout board, good for enclosures, and also for Manhattan construction. The lesser thicknesses would probably only work for small enclosures, but would be fine for most circuit construction, unless you’re using a larger board and specifically need something inflexible (a thicker board would probably be more stable for a regen, for example). Up until now, I have used 0.06″ board for both enclosures and circuits, but a friend recently gave me some really nice pieces of thinner board (about 0.04″, I think), which I will use for building circuits on. When buying from abcfab, my standard order is for 0.06″ thickness, 1oz/ft² weight copper, single-sided, FR-4 substrate material. FR-4 is a composite of woven fiberglass cloth with an epoxy resin binder that is flame resistant (hence the FR designation). He also has a few different colors, which are fun for enclosures. I have bought red, blue, and the usual light brownish-colored boards from him. I did try to find a supplier for small quantities of other colors, such as orange, but the only way I found to do it was to buy whole sheets from a supplier and have them cut down to size, either for my own stash, or perhaps to also distribute to other home-brewers to spread the cost out a bit.

I won’t go into detail on enclosure building here, but I talk about my methods in this post. Ken WA4MNT has an excellent tutorial here. I learned most of what I know about building PCB enclosures from Ken’s tutorial. Ken uses shears to cut his material. I found that scoring it deeply on both sides with a box cutter allows it to be flexed and snapped cleanly. Running a file over the edge gives a nice result.

Anyway, a little about building circuits, which is the main subject of this post. Here are my main tools –

At the top is a 2.25mm crochet hook, used for winding toroids. I use the hook to pull the wire through the toroid, which is a great way of keeping the turns snug against the core. Beneath it, from left to right, is a tube of superglue gel. The gel form works best – the liquid is just too runny and gets everywhere. Next is a pair of round-nose pliers with round cross-section jaws (Pro’s Kit 1PK-29). I use these for bending component leads for the rounded look –

Round component leads on the Etherkit OpenBeacon

Next to the rounded pliers is a pair of green-handled Xcelite MS543J flush cutters with ESD-safe cushion grip handles, and a couple of small jewelers screwdrivers (from a cheap set bought from Radio Shack), which I use for scraping lacquer off the board in the places where Manhattan pads will be glued, as well as pressing down on the pads when gluing them to the board. Then a pair of Pro’s Kit 1PK-036S long nose pliers. I didn’t like the spring action, so I removed the spring from the handle. Next is a red-handled pair of needle nose pliers (cheap ones from Radio Shack). On the far right is a craft knife or as some call it, a box cutter. In the UK we call them Stanley knives, after the brand – in the same way that the British also call a vacuum cleaner a Hoover, and we in the US talk about Scotch tape, while the Brits refer to the same thing as Sellotape. This craft knife is used to deeply score both sides of a piece of PCB material before breaking it cleanly off. You’ll go through blades fast with this method. I bought a pack of 100 blades as typically, I find that every time I score a board enough times on both sides so that it can be broken off, I need to replace the blade. Blades are cheap when bought in bulk, and it’s not worth putting up with substandard cuts just in order to save a few pennies.

Looking at the needle nose pliers a bit closer, you’ll see that I filed flats into the ends. This has nothing to do with Manhattan construction. I needed a specialty tool to remove the nut holding a VFO encoder pot on a Yaesu FT-817, and found out that after filing a couple of flats in the jaws of these pliers, they fit the cutouts in the pot nut perfectly, allowing me to use the pliers to unscrew the nut –

The round-nose pliers in the foreground, and the needle nose pliers in the background.

I forgot to photograph my steel rules. I have 3 of them – a 12″ one marked in mm, a 6″ one also marked in mm, and an 18″ one marked in inches. They are used for scoring the lines in boards when cutting the PCB material and, of course, for all other kinds of measuring applications.

Moving along, at the top of the next picture is a T-handled reamer. This is used for making larger holes in chassis and enclosures. I start out with a drilled smaller hole, and enlarge it with the reaming tool. The brand name is General, and it is a No. 130. Then from left to right are a couple of files – a mill bastard, and a half-round bastard. The hand drill (and set of bits at the far right) is much used for drilling holes in enclosures. Finally, in the middle is a set of small files, which are very useful for finishing off all kinds of holes and rough edges. This particular one is made by General #707476 and is called a 6-piece Swiss Needle File Set –

When gluing Manhattan pads down, I first scrape the lacquer away from the board with a small jewelers screwdriver in the area where the pad will be glued. I know you’re not supposed to use screwdrivers for scraping things, but these were from a cheap set. I also roughen up the underside of the MeSQUARE or MePAD with a sharp craft knife blade to help adhesion. I put a small drop of superglue gel in the center of the area on the board where the pad will be, and lower the pad into position with the long nose pliers.

This next part is tricky. Once you begin to push down on the pad, you only have a few seconds before it is glued fast to the board. The trouble is, that as you push down on it (with a screwdriver or whatever other implement you’re using), the pad tends to slip around on the gooey gel, and change position. If you’re fast, you will have time to re-position it as it does this. You achieve this with a combination of pushing down slowly, and quickly re-positioning it by nudging it with the screwdriver. Once you start pushing down, the clock is ticking. You’ll have time to re-position the pad if necessary, but you’ll have to be fast! The good news is that if you do succeed in gluing the pad down in the wrong place, you can remove it and try again. Just wait a couple of minutes for the glue to set, then slide a sharp craft blade under the pad and pop it off the board. Be careful when doing this so that you don’t slice a finger, or slip and damage something else on the board. Once the pad is off, you can scrape away any remaining glue and go for a second try.

Component leads can be pre-cut and pre-formed with the cutters and pliers, and then placed against the pads and board to check the fit, before soldering. A few folk have asked how to actually get the parts standing up on the pads in exactly the position desired. This is the wonder of tack-soldering. Most modern components come with the leads already pre-tinned. For the purposes of tack-soldering though, it helps to have just a bit more solder on them. Once you have tinned the lead(s), you can place the part in the position you want it using a pair of pliers (or other tool), and temporarily fasten it in place with a bit of heat from your soldering iron. Then you can either tack-solder or permanently solder the other lead into place, after which you go back to the first lead and make that solder job permanent. As well as using pliers, I often use jewelers screwdrivers to coax leads into the right positions – use whatever you have, and whatever works for you. You’ll develop your own techniques over time. It can be a slow process, often taking many years, so don’t despair – enjoy the journey!

Oh, I forgot to mention the soldering iron. A temperature-controlled soldering station is preferred over a cheaper iron without temperature control. A temperature-controlled iron can deliver more heat when needed, such as when soldering to a circuit board ground plane. It’s surprising how much heat even a small ground plane on a circuit board can “sink” away from the tip of a soldering iron. The station I use is a Hakko 936. I don’t believe they make that model any longer, but there are plenty of affordable soldering stations available, for around the $100 mark. As for tips, chisel tips are good for most purposes. I use a 1/16″ chisel tip for most things, switching to a smaller 1/32″ chisel tip for the more fiddly tasks. The flat sides of a chisel tip will allow you to transfer heat more effectively to the area being soldered than will a conical tip.

Oh, and test gear. The most important piece of test gear by far, is a multimeter. I have a 20 year-old analog multimeter from Radio Shack, which used to be my main meter. Nowadays, I mainly use it for the times when I’m peaking circuits, when being able to see a needle move on a scale makes it easier to adjust a control for a peak or a null. My main meter now is a cheap manual DMM, an Extech MN35. It was a gift from my friend Antoinette last Christmas. IIRC, they are about $25 –

Most folk seem to prefer auto-ranging DMM’s. My preference is for a manual, as I like the manual control. Whether you are using a manual or an auto-ranging DMM, you should have an idea of roughly what kind of voltage you expect to find at a particular point before poking the test prods anywhere near it. Knowing what voltage (or current, or resistance) ball-park you are in, it is no trouble, in my opinion, to switch the meter to the appropriate range. That may be just be my justification for the fact that I’m rather stuck in my ways, and just happen to prefer manual meters. It’s convenient that they are cheaper too :-) With a DMM like this as your sole piece of test gear, you can build an awful lot of stuff. There are cheaper DMM’s out there, but the really cheap ones have low build quality and poor accuracy, in my experience. I do also have an old Tek 465 oscilloscope which a local ham very generously gave me. Combined with a signal generator, you can do all sorts of fun things with a ‘scope, such as injecting a signal into an amp stage, and seeing what it looks like when it comes out (as well as calculating the gain of the stage). I recently used it to measure the output of a 5mW QRPp transmitter, by measuring the peak to peak voltage across a 50 ohm resistor. At such low output powers, RF probes aren’t accurate, and a ‘scope is a good way to go.

My DMM doesn’t measure capacitance, so this capacitance meter does a great job. I often check values of components before installing them into a circuit, as a double-check to ensure I didn’t misread the value printed on the part. I got this one for a little under $15 from Sparkfun. It measures capacitances from just a few pF up to many uF’s –

There are some really useful cheap pieces of test gear on eBay. I plan to ask for a little frequency counter, and maybe also an ESR meter for Christmas.

Anyway, the purpose of this post was to show you the tools I use for my home-brewing activities and hopefully, to demonstrate that you don’t need a lot of expensive ones to build a lot of cool things. However, if you have the interest and can afford it, feel free to get yourself lots of cool test gear!

Those are the basics, I think. I cannot think of any more right now. If you have any questions, feel free to ask them in the comments section and I’ll do my best to answer.

October 21, 2015

How Do Lacquered Boards Stand Up Over Time?

A query I hear from time to time about using copper-plated boards for Manhattan construction is what they look like after a few months or years. “How do they age?” is the question. My first such project, the WBR, was housed in an enclosure made from double-sided PCB material, and I could see that the outer surface had developed a bit of oxidation; a certain patina, if you will. My later projects weren’t made from this double-sided PCB – just single-sided, so I was going to have to open them up to see how they’d fared. Comparing how they looked, and remembering how I’d applied the lacquer to each did help in coming to some conclusions.

First of all, this is how the outside of the WBR looked shortly after I finished building it just over 4 years ago. It was already showing a few early signs of oxidation. However, it did fit together very well, and made quite a handsome enclosure –

The WBR in July 2011

I made 2 mistakes with this enclosure. Firstly, although the initial cleaning of the boards was done with Scotch-Brite scouring pads, the final cleaning was with Tarn-X. I later found that copper boards cleaned with Tarn-X develop streaking and oxidation. The streaking on this WBR enclosure was not anywhere as near as bad as I have seen with other boards, but it is definitely there. You can see it on the side panel in the next shot. The other mistake was to spray the lacquer too lightly. I was cautious about spraying it too thickly and causing it too pool, so I erred in the other direction instead. This is what it looks like from the outside today. Not bad, but definitely aged. You can see the areas on top where my fingers press against the case when I pick it up –

The WBR today (Oct 2015)

Here are a few more.

Before (July 2011) –

The WBR today (Oct 2015)

and today (Oct 2015)  –

The WBR today (Oct 2015)

The WBR today (Oct 2015)

If I were making the WBR again today, I’d stay away from the Tarn-X, and apply slightly thicker coats of lacquer.

Next, I decided to open up The Rugster. It was a little direct conversion receiver I had made by teaming up a standard NE602-type DC receiver front end with NM0S’ Hi-Per-Mite filter, set for maximum gain, so as to provide both 50dB of gain and narrow filtering. I built it into an enclosure made of single-sided copper-clad board on a red laminate. It had a really cool and compact look –

The Rugster in July 2012

It still looks the same from the outside today, but I was curious to know what the interior looked like. This was what it looked like when freshly-built 3 years ago, in Aug 2012. The treatment of the VFO toroid was my first ever attempt at using a hot glue gun, by the way. I am more skilled at it now. This particular toroid looked a bit of a mess –

The Rugster today (Oct 2015)

The same view today (Oct 2015), looking remarkably good. You can see that I added a high-pass filter on the back panel set to block signals from the AM broadcast band –

The Rugster today (Oct 2015)

I do remember that I sprayed slightly thicker coats of lacquer than on the WBR, leaving each coat for about an hour before spraying the next coat. Here are some more “after” shots –

The Rugster today (Oct 2015)

In the next one, the brighter patch on the red front panel is a splash of morning sun, and not a discoloration of the laminate –

The Rugster today (Oct 2015)

The 3rd project to be given a second look was the VK3YE Micro 40 DSB transceiver, which I built 2 years ago, in Oct 2013. Back then, the innards looked like this –

The VK3YE Micro 40 DSB Transceiver in Oct 2013

A couple of days ago (Oct 2015), it looked like this –

The VK3YE Micro 40 DSB Transceiver today (Oct 2015)

The VK3YE Micro 40 DSB Transceiver today (Oct 2015)

I used to clean my boards with Scotch-Brite pads but now find that fine steel wool scouring pads work even better. Then, when they’re clean, I dry them with clean bathroom tissue, making sure to blow any loose fibers off afterwards. Then I spray the first coat of lacquer. To this day, I still don’t always judge it correctly, and end up with boards that don’t age too well, but IMO, it is best to spray until it is just beginning to pool, ever so slightly. At this point, the lacquer is quite thick, but will smooth out before it dries. An hour later, you can spray the second coat. I’ll leave it up to your judgement as to whether you apply a 3rd coat (I usually do). From my experience, this way works quite well. I’ll be interested to hear details of anyone else’s experience with lacquering.

In the next post, I’ll talk a little about the methods I use when constructing Manhattan boards.

October 6, 2015

Some More Sproutie MK II Videos

Since finishing The Sproutie MK II and publishing the blog-post on it a few weeks ago, I have been listening to it, winding an extra coil or two, and also attempting to tweak the active audio filters. Coverage of The Sproutie is now up to 18.3MHz, and while I know from previous experience that it will cover up to 30MHz, I am going to leave the upper limit where it is for the time being. Any new coils will most likely be wound for more limited coverage on specific bands under 18MHz. PS – I just spent part of the morning testing out the upper limit of the newest coil by listening to SSB on 17M, and it’s working great – quite stable too.

I had wanted to give the CW and SSB active audio filters more gain, to compensate for the fact that in those modes, the RF gain needs to be wound down to prevent oscillator pulling. Because the narrower filters, even if they have the same gain as the wider filters, give the perception of lower volume, I wanted to design them with higher gain to compensate. Currently, the narrowest filter, a 700Hz low-pass, has a gain of 20dB. I tried building 700Hz low-pass filters with gains of 46 and 34dB, but they both oscillated, putting out a square wave with 10V amplitude at a frequency of somewhere in the region of 100-150Hz. I made sure to keep the Q below 3 – in fact the highest Q stage in the 34dB filter was just a little over 2, but this didn’t help any. For the time being at least, I have decided to keep the current filters as they are. If you view the videos, you’ll see that The Sproutie does indeed work on SSB and CW. If receiving a weaker station for which the set could use a little more gain, plugging headphones in helps and at this point, it’s a compromise I’m willing to make. Trying to build the perfect regen is a rabbit hole from which it sometimes feels as if there’s no escape, so I decided to draw a line in the sand and leave things as they are.

Once again, I feel as if I should apologize for the quality and resolution of these videos. I just entered the 21st century a few months ago with the acquisition of my first smartphone, a first generation Moto G. It’s a budget model, so doesn’t have the best video. It is an improvement on the videos I used to post from my decidedly old Canon Powershot A80 though. The one thing the videos do achieve, I think , is to give you some kind of feel for what the receiver is like to operate. For detailed views, the still photos are the way to go.

This one shows how a regen, if you nudge it into gentle oscillation, can provide some carrier injection for reception of weak AM stations –

Here’s the 25M SW broadcast band –

And another video on the 40M amateur band on CW and SSB, with a special brief guest appearance by Jingles the blind kitty –

September 14, 2015

The Sproutie MK II HF Regen Receiver

NoteIf you have read this article before and are checking back in, it would be a good idea to clear your cache, to ensure that you are viewing the very latest version of this post. I do add material and make corrections from time to time.

It’s been about a year since I finished building The Sproutie, and it’s been a good year. Of all my scratch-built projects, it has been the most satisfying to own. It works well, looks pretty good and also, there is always the lure of possible of tweaks and improvements. This is partially because it’s a home-brew project, and also because it’s a regen :-) It was really enjoyable to build a receiver with the basic circuit architecture taken from the 1930’s, but with a combination of solid state devices and lovely old vintage parts.

I have continued to occasionally purchase vintage reduction drives and variable capacitors. After using a National N Dial for the main tuning control in The Sproutie, I became quite pre-occupied with what, to me, is close to the ultimate dial and drive for an analog receiver – the classic National HRO micrometer-type dial and gear drive. I wanted to find a good example of one of these, and use it in a regen.  I also spent quite a bit of time performing Google searches using phrases such as “best regen receiver ever”, and “the ultimate regen”. These are the kinds of things I search for when at a loose end, in the vague hope that I’ll magically find the most amazing regenerative receiver ever designed and built! One very inspirational regen I did discover while searching for the “ultimate regen”, was Jim K4XAF’s build of Bruce NR5Q’s “Ultimate Regen”. What a beautiful receiver! It’s a tube set, built on 2 separate chassis. One chassis contains the main receiver, while the other houses the power supply, the speaker, and the “Selecto-O-Jet” audio filtering. It makes use of a National HRO dial and gear drive for the main tuning, along with National “Velvet Vernier” drives to control the regeneration and variable antenna coupling. Now this was the type of regen that inspires true longing, and convinced me that as enjoyable as The Sproutie was to build and own, I needed to build just one more regen :-)

Initially, I was hoping to use a different type of circuit for this receiver from the tried-and-tested front end used in The Sproutie. I did build VE7BPO’s regen #4 and had some trouble with it picking up a local FM broadcast station. In retrospect, I should have realized that I have had this issue with other simple receivers at this location, until they were cased up and grounded properly. The problem seemed to be a little worse than normal, but this could well have been due to the amplification factor of Professor Vasily Ivanenko’s hycas detector. I gave up far too soon and headed for the security of the front end I used in both the first version of my Sproutie, and the WBR. It is, of course, the circuit used in Nicky’s TRF, as featured in issue 70 of SPRAT (with a few corrections and suggested mods in issue 72). Incidentally, “Bear” NH7SR built a very functional version of Prof V’s Regen #4 which he described in this thread over on The Radio Board.

However, I didn’t just want to exactly duplicate the circuit of The Sproutie, even if the new receiver was going to have a different physical form and different hardware. This new receiver would have to have some alternate type of circuitry that would make it worth building. I was interested in trying a different type of filtering in the audio chain, and a tip from Prof V in his Solid State Regenerative Receivers group on Google+ clued me in to a great tool for designing active audio filters (more on that later). The pieces were beginning to come together. I had a bunch of NE5532’s in my parts stash that had sat unused for a couple of years and it struck me that a regen which utilized a series of active audio filters for different bandwidths, switched from the front panel, might be an interesting idea for a receiver. The LM380 output stage I had used in The Sproutie works well, so I saw no reason to change it. It is fairly low noise, a welcome factor that makes it possible to listen to a receiver comfortably for long periods of time.

Here’s the block diagram of The Sproutie MK II. As it contains 6 separate AF filters, I decided to also switch the +ve supply to the filter. A 5532 active filter draws about 7mA (14mA if using 2 x op-amp stages). Although it’s not a lot of current, it’s a fairly significant amount relative to the total consumption of this receiver if all 6 filters are continuously powered. One of the reasons I prefer solid state over tubes is the power efficiency, so no reason to keep all 6 filters powered if only one is being used at a time –

Fig 1 – Block diagram of The Sproutie MKII. Note that S1a, S1b and S1c are all part of the same rotary switch.

The front end, as I mentioned, is exactly the same one I used in the original Sproutie. It is the one used in Nicky’s TRF featured in issue 70 of SPRAT. I thoroughly recommend joining G-QRP. Your initial membership includes an archival DVD of past issues of the club magazine SPRAT, which is a very valuable resource for homebrewers. If you have access to this archive, you should also take a look at issue 105, in which a slightly different version of the same receiver is featured. It employs a simple passive LC audio filter, if you’re not keen on the extra complexity that my version here entails.

Here’s the schematic of the front end. The oscillator tank circuit has been simplified to just one variable capacitor, and all details of the plug-in coils removed, purely for the purposes of making the circuit a bit easier to understand. If I drew the octal coil socket without the coil (as I did with the schematic for The Sproutie) it would make the process of understanding the circuit diagram a bit less intuitive –

Fig 2 – The Sproutie MKII front end, with details of plug-in coils and fine tuning capacitor removed for simplicity.

Here are details of the coil base, using an octal tube socket. You can use any pin configuration you like – this is the one that worked for me. It is the same configuration as used in The Sproutie –

Fig 3 – Plug-in coil base wiring

The final AF amp is a simple LM380 circuit. It’s easy to build, is fairly low-noise, and it works. As well as a phone jack, I included a jack for an external speaker on the rear panel. It took me a while to figure out how to wire the internal speaker and the 2 jacks properly.  I wanted the internal speaker to cut out if either headphones or an external speaker were plugged in. I also wanted the the external speaker to cut out if the headphones were plugged in. It’s a simple problem really, but simple things often elude me. I got there in the end –

Fig 4 – The AF output stage. The “bass” switch only gives a very gentle lift to the lower frequencies. The effect is so subtle that you won’t be missing much if you leave it out.

The thing that makes this receiver different from the original Sproutie, electrically speaking, is the bank of switched active audio filters. If you don’t want to be bothered with building multiple filters, and switching them all with a switch, you could permanently wire just one filter into the circuit. Another idea would be to replace this bank of switched filters with an adjustable filter made from op-amps, with the center frequency and bandwidth controlled by potentiometers on the front panel. Once you bring op-amps into the mix, all sorts of things are possible. Another idea suggested by Bear NH7SR, is a 5KHz audio notch filter, which could be quite useful for AM SWBC listening. The design tool that made all this happen for me was by Texas Instruments (thanks Prof V). There is an online version called Webench Filter Designer. It has a user-friendly interface that actually made the process of filter design harder for me than the offline software they also offer, called Filter Pro. Use which one works best for you – they are both accessible from this page (opens in a new browser window). Of the two, I recommend Filter Pro. You can use this software to design low-pass, high-pass, bandwidth, allpass (time delay) and notch filters. I stuck with low-pass filters. I was tempted to try a bandpass design for the CW filter, and may still do at some point. The CW filter I constructed was the very last filter out of 6. By that time, I didn’t have the patience for the slightly more complex design of the bandpass filter. I also rationalized that I might need to tune through a CW signal to hear the other side of it, if trying to escape QRM, so a lowpass would make this easier, as I’d be able to hear the signal all the way through to zero-beat and out the other side. This might simply have been my excuse for not wanting to build a bandpass filter :-)

I wanted a “straight-through” position to give me something to compare the other filters to. All the filters, with the exception of the narrow CW filter, were designed with a 6dB gain, so I designed my “straight-thru” filter with a 6dB gain also, so I could step through the bandwidths seamlessly. If doing this again, I would have given the filters a bit more gain. I’ll explain why later. Dan N7VE gave a talk to the Arizona QRP Scorpions a few years ago on (among other things) designing active audio filters. It’s definitely worth taking a look at his presentation, which is available here. In fact, I wish I’d paid attention to it before embarking on designing the filters for this receiver, as I would have tweaked some of the resistor and capacitor values a bit. Dan explains how it’s desirable to keep the resistors in the main signal chain fairly low in value, to avoid noise. He recommends trying to stay under 1K. I only read the presentation before designing the very final filter – the CW one with a cut-off of 700Hz – so while my resistor values in that filter are nice and low, they are not quite so low in the others (though in my defense, they are not atrociously high either).

Here’s the first, and widest filter. As far the ear is concerned, it’s not really a filter, as it has a cut-off set at 20KHz, with a gain of 6dB –

Fig 5 – The “straight-through” filter (an LPF with a cut-off of ~20KHz)

I wasn’t interested in the shape of the response as, for this stage, all I wanted was effectively an unfiltered stage with a gain of 6dB. For this reason, I used just one half of a dual op-amp 5532 package as a real-pole filter. Filter Pro doesn’t show the power supply and biasing arrangements, so I added the 2 x 47K resistors to keep the input biased at about half of the supply voltage. I also added the 10uF capacitor, which keeps the bottom end of the 1K resistor at ground potential for audio signals, while blocking the DC bias. I also added the lowpass filter formed by the 10 ohm resistor and the 100uF electrolytic on the supply line, as well as the 0.1uF ceramic RF bypass cap on pin 8 of the IC (mounted close to the pin). I don’t know how essential these 0.1uF caps are, but the datasheet suggests them, and they can’t do any harm.

The other filters were all 4th order low-pass filters (2 stages = 1 x 5532 dual op-amp package), with the exception of the 2.4KHz filter, which was an 8th order low-pass filter (4 stages = 2 x 5532 dual op-amp packages). The 8th order filter has a sharper cut-off, of course. Feel free to design your own filters, with the help of Filter Pro, for whatever cut-off frequency and rate of roll-off you wish. I’ll show you the R and C values I used for my filters but you might want to fiddle around with the software and come up with your own values that keep the R values in the main signal chain at or below 1K, if possible. The resistors in the first stage of the filter are particularly important, as the noise they produce is amplified more than noise produced in later stages. Just click on a component in Filter Pro, enter a different value, and hit return to see what new values of the other components the software has calculated. A bit of trial and error should get you close. Also note that you can specify the series of resistor and capacitor values you want to use (E96, E48, E12 etc), and watch how the filter response curve changes as you change the tolerances and values.

First of all, here’s the gentler roll-off 4th order filter that uses just one 5532 8-pin dual op-amp IC – or use the op-amp of your choice. I chose the 5532 because I had a bunch of them in my parts stash and because they are the 2N2222 of the op-amp world – plentiful, reasonably priced, and all over the place –

Fig 6 – Schematic for the gentler roll-off 2-stage LPF

Here are the component values I used for my 4th order filters –

Fig 7 – Component values for the 2-stage filters in my Sproutie MK II

For a sharper roll-off, an 8th order filter, which uses 2 x 5532 dual op-amp packages (or equivalent) –

Fig 7 – Schematic for the 4-stage sharper roll-off LPF

The 2.4KHz 8th order filter I used, although a bit on the narrow side for SSB, is good for listening when there are nearby stations higher in pitch that need cutting out. If you think about it, this 2.4KHz LPF is going to sound roughly like the 2.1KHz filter in a regular SSB rig. The reason for this is that your regular SSB filter is a bandpass filter, with the bottom edge being set to cut off at about 300Hz. This means that a 2.1KHz SSB bandpass filter will pass frequencies up to about 2.4KHz (2.1KHz + 300Hz). Here are the values I used in mine –

Fig 8 – Component values for the 4-stage filter

After I had built the receiver and all these filters, and done some listening, I concluded that for SSB and CW, a bit more filter gain would be helpful. The set has plenty of gain when listening to AM but on CW/SSB, the RF gain has to be wound right down to prevent the oscillator pulling. This creates a need for more AF gain in the CW/SSB modes. At the time of writing this, I have only just finished building this set and have no enthusiasm for building more filters. I actually had to build 8 filter boards to get the 6 that I used, and 3 front end boards to arrive at the final one. Together with the physical side of the construction, I am tapped out right now and have no desire to construct anything else at all for a while!

If you want to use this receiver mainly for SSB and/or CW, you may want to experiment with the value of the NPO capacitor in the front end that connects the hot end of the main tuning coil to the base of the 2N3904 oscillator transistor. It is listed on the schematic as being 39pF, and that is the value I used. However, it is possible that a lower value will cause the oscillator to pull less on strong signals. Of course, the lower value might also reduce the signal strength into the detector which will put you back to square one. It’s worth trying though. I’d be tempted to try a value as low as just a few pF. Remember that changing this capacitor will affect the frequency coverage – particularly at the top end of each range.

When building the filters, I originally built the 700Hz CW filter with a gain of 6dB, like the other filters. The idea is that if they all have the same gain within their passband, the operator can step through the different bandwidths without a change in the volume of the wanted signal in the speaker. This was the way it worked except with the 2 narrowest filters. The 2.4KHz 4 stage filter had a slight, but noticeable drop-off in volume. The effect was very pronounced with the 700Hz filter – so much so that I redesigned it with a gain of 20dB and still found that there was a slight drop-off in volume within the passband as compared to the other filters. I don’t know the reason for this. EDIT – Thomas LA3PNA Tweeted the following explanation – “The perceived loss when changing filters is because the power delivered to your ear is 10log(BW of filter) and less with less BW. So basically, the reduction in noise makes it sound like the volume goes down”  He also gave a very useful tip for adjusting the gain of the filters so as to preserve the perception of constant volume – “I like to add gain in a filter circuit after the formula 20log(bw/orginal bw) for AF filters”  That is very useful information Thomas. I’m a little tapped out after building The Sproutie, but if and when I decide to revamp the filter bank, I’ll be paying attention to this formula.

I may, at some point, rebuild the 3 narrowest filters with higher gains. If that ever happens, I’ll report the results here in this post. Incidentally, at this point, allow me to say one more thing about the filters. If building and wiring up all these filters sounds like it is making the construction of a regen overly-complicated, I can definitely sympathize. If you want to use this set for CW, SSB and AM and you want to permanently wire in just one filter, I’d go for a 4th order (2-stage) LPF with a cut-off of 3KHz. The one I have is perhaps a touch wide for SSB (it’s roughly equivalent to a 3.3KHz passband filter, as explained earlier) and a bit narrow for AM broadcast, but it’s a good compromise for both. If it were the only filter I had, I know I would get used to the sound of it. As for the gain, mine has a gain of just 6dB, but I’d like to up it in order to have a good volume when turning the RF right down, as is necessary to prevent oscillator pulling on SSB/CW. I can’t know until I’ve tried it, but I’m thinking something along the lines of 26dB gain. Just make sure to be careful when on AM, as you may find that you have way more gain than you need – so keep an eye (and a hand) on that RF gain control.

A big part of the inspiration for building this receiver, as I mentioned earlier, was the physical form of K4XAF’s version of NR5Q’s Ultimate Regen. In the search for a National HRO dial and gear drive in really nice condition, I bought several, and finally came up with a dial and drive combination that just cried out to be included in this receiver. This gear drive has a shaft rotation limiter, which was perfect, as the tuning capacitor I wanted to use didn’t have any kind of rotation limiting built in – it was the capacitor in the first photo in this post – a Hammarlund MCD-50-M. The final M stands for midline, referring to the fact that the off-center shaft and shape of the vanes help to make the tuning a lot more linear than with regular variable capacitors. With a standard capacitor, you’d find that the frequencies would become very compressed at the top of the tuning range i.e. the tuning would get a lot more fiddly. Try to get a midline unit. I believe they also go by other names, depending on the manufacturer.

Of course, a big dial and gear drive need a big chassis, and Terry from Seaside Chassis, who made the chassis for The Sproutie, came to the rescue again. I decided to use a chassis and front panel that would be compatible with 19″ rack cabinets, for a variety of good enclosure options. A chassis that big needs to be fairly thick in order to still be stout and solid. Terry does offer the use of 12 gauge aluminum for bigger enclosures, and I wanted this receiver to be big and solid (although compared to your average boat anchor, it’s still relatively light). As well as a large, stout chassis, I decided that I wanted to try designing a custom front panel with the services of Front Panel Express in Seattle using their free design software. Right at the beginning of this whole project, in the first month or two of 2015, I downloaded their software and casually laid out a very rough front panel, mainly for the practice, and the fun of learning something new. As the project progressed, I’d spend a few weeks working on circuit boards, then go back to the front panel, then do a bit of work on the plans for the chassis, to send to Terry. I had an idea that, with a bit of luck, I’d complete the whole thing in or around the fall, and that’s how it worked out. At no point did I rush though. Why rush? Besides, the longer a project takes, the less it costs per month. I could see that building this regen in the way I had chosen to build it was not going to be a cheap affair, so I took my sweet time.

Here is the chassis as it arrived from Seaside Chassis, along with 2 side braces for supporting the front panel, 2 mounting brackets for the main tuning capacitor, and 2 mounting brackets for the regeneration pot. I only needed 1 of each of these brackets, but like to have extras on hand. As it turned out, an extra bracket was needed to help secure the main tuning capacitor which I forgot to ask Terry for, so I put in an extra order. The shipping from Canada dwarfed the cost of the bracket but at this point, it was easier to ask him for it than to find someone local and besides – I just wanted him to fabricate all the chassis components. Terry’s work is first-rate. It’s good to give him as much relevant information as you can. Simple drawings with penciled-in dimensions work well. If it’s important to you, remember to take into account the thickness of the aluminum if there are any dimensions that are particularly critical. Also remember that he is bending and fabricating these components by hand, so allow for a certain amount of tolerance in the final dimensions. Having said that, the chassis he supplied was remarkably close to the exact dimensions I requested, and within the tolerances I had allowed for. If you have any dimensions that are particularly critical or non-critical, I think this is all good information to pass onto him when making your request –

Figuring out exactly where to drill holes for controls in front panels and enclosures usually takes quite a lot of time. It’s a bit like a game of chess in that every decision you make affects everything else down the road. To make matters tougher, I have trouble thinking about more than one thing at a time, so juggling all the variables in my head takes a lot of thinking, measuring, and drawing. For front panels, I always draw the shape of the panel on a full-size sheet of paper, and place all the knobs and controls on it to see how they look in various configurations. Just when I think I have it right, I leave it and walk away, often overnight. On returning, I inevitably come up with an improvement or two. Building something like this is all baby steps for me. I am impressed and amazed by builders who claim to be able to throw something like this together in a few afternoons – this one took me over 6 months. Heaven knows how long a more complex receiver, such as a multiband superhet, would take me.

I took a great deal of time and care in designing the front panel. They are worth every penny, but they are not cheap. I didn’t want to make a mistake that would result in having to re-order the whole thing. So after checking, rechecking, going to sleep, then waking up and rechecking again, I went through this whole process several more times before finally clicking “order”. A week or so later, this beautiful 4mm thick aluminum panel arrived via UPS, packed with a little bag of gummie bears –

Gummy bears!

The front panel as it arrived from Front Panel Express, vacuum packed to a stiff baseboard. The metal ruler is 18″ long (the panel is 19″ wide).

Look at this beautiful, black anodized front panel!

I just couldn’t get enough of this thing when I first saw it –

There were some scratches in the black finish on the rear, but this is normal. I later found out that  it is possible to add a note when ordering, to ask the people working with the milling machinery to take extra care with the back side of the panel. The front surface is guaranteed, but not the back.  I decided I was OK with the rear of my panel as, well, it was the rear, and the bottom half of it would be in direct contact with the front of the chassis anyway –

You’ll notice a number of “blind” holes milled on both the front and rear. The panel is so thick (4mm) that controls sticking through both the chassis and this panel wouldn’t protrude far enough for the nuts to thread onto the bushings. For the RF gain, AF gain and filter rotary switch, the blind hole was milled on the front side, as the knob would cover it. For the phone jack and bass switch, the blind holes were milled on the rear. Here’s a close-up of the blind hole on the rear side for the bass toggle switch. You’ve probably figured (if you didn’t already know) that a “blind” hole is one that doesn’t go all the way through the panel –

After the initial euphoria of receiving this fantastic front panel had subsided a little, it was time to put some time and labor into making all the remaining cut-outs in the chassis. I had asked Terry to make the holes for the octal tube socket and the main controls, but there were others that still needed to be done. My usual method of making non-standard cut-outs and holes is very time and labor-intensive, but it works quite well. I mark the edges of the cutout with a pen or pencil, then with a hand-drill, drill lots of small holes around the perimeter. Then, with an old screwdriver, I knock out the piece of metal in the center, and clean up the edges with files, usually using a bastard file first, and finishing off with something finer. These photos should help illustrate the process. The speaker cut-out was inspired by a WW2-era British military R107 receiver that I owned as a teenager. It is simple – just 4 large holes arranged in a square. This is the “during” photo, showing the series of small holes drilled around the edges of the holes. The rectangular cut-outs to the right were made using the same technique, incidentally –

– and after –

Here’s another photo, taken a bit later during the assembly, showing the placement of some of the main components. This particular National HRO NPW gear drive, unlike most that I have seen, has a shaft rotation limiter. The tuning shaft is a little on the short side. I needed to mount the gear box as close to the front panel as possible in order to be able to mount the dial properly. If you scroll back and look at the photos of the front panel, you’ll see there are 3 smaller holes located around the main hole for the gear drive. These holes helped in locating the gear box as close to the front panel as possible (the 3 screw heads fit into the 3 smaller holes on the front panel). Most of these gear boxes don’t have this rotation limiter, so the extra holes won’t be necessary. Also, do you see the aluminum shaft couplers on the regen pot and fine tuning capacitor? Those are quality parts personally machined by John Farnsworth KW2N. The one on the right is a standard 1/4″ to 1/4″ coupler, while the one on the left was made to order. It couples the 1/4″ shaft of the 10-turn regeneration pot to a short 3/16″ shaft that the National knob fits onto. I wanted to use the same type of National Velvet Vernier knob and escutcheon plate for the regeneration that I used for the fine tuning, but I didn’t want to use the 5:1 reduction drive. I wanted to use a 10-turn wirewound pot instead, as I like the feel of those pots. From the front (as you will see in later photos) the 2 National knobs and escutcheon plates look the same. However, the knob on the left is connected directly to the 10-turn pot and not to a National Velvet Vernier reduction drive. The black escutcheon plate for the regen control is spaced away from the front panel by one washer thickness, and bolted to the front panel with 4-40 hardware. It is not used for anything, other than looks.

Now, let’s look at some of the boards. They were built, as always, with W1REX’s very useful MeSQUARES and MePADS. This is the AF output stage and the 4KHz filter mounted on one board, and installed in the chassis. The idea was that this board, together with the main RF board, would form a working receiver, after which I could build and install the other filters, one by one –

Mounted above the AF output stage, on the stand-offs, is this next filter board, carrying 2 LPF’s. The first filter to be built was the 6KHz one –

Next came the 3KHz filter (in the foreground of the next shot). The grey rectangular poly capacitors were from Tayda Electronics. Thier prices are low, and the caps seem good. The resistors are 2 types – either 5% carbon film from the parts stash I had as a kid in England in the early 80’s. They lasted a long time, but I am beginning to run out of them. The others are newly-acquired Xicon 1% metal film parts, purchased in lots of 200 from Mouser –

The same board, taken from above (3KHz filter on the left, 6KHz filter on the right) –

The same board, with the 3KHz and 6KHz filters, mounted in the chassis above the 4KHz filter and AF output stage –

Here are 2 shots of the 4-stage (8th order) 2.4KHz LPF, with temporary leads in place for testing. It’s quite the QRM-buster –

At this point, allow me to introduce the main RF board. Electrically, it is exactly the same as the one in the original Sproutie. I tried a couple of small mods but went back to the original. So – nothing new here, except for a small physical detail that I learned from my experience with The Sproutie. There are 2 pads on the board that connect to the octal tube socket with (ideally) short, stiff wires. In the original Sproutie, I used very short lengths of solid 16 gauge wire. They were so stiff that, over time, with repeated insertions of coils, the wires placed enough stress on the pads to detach them from the board. It took me a while to figure out why the dial calibration was suddenly off by about 10KHz. The pads had only separated from the board by 1mm at most, so it was hard to see, but it was enough to throw off the dial calibration, and cause it to change slightly in an unpredictable fashion. I did 2 things to remedy this. The first was to replace these 2 wires with thick stranded wire, which I tinned thoroughly. The tinning stiffened the wire, but it still had more flex than the original solid 16 gauge wires. Secondly, I removed the 2 pads, and re-attached them with epoxy instead of superglue. Problem solved!  When I built the Sproutie MK II board, I attached these 2 pads with epoxy (I used JB Weld). Superglue gel was used with all the other pads, as before. The 2 pads in question are at the very front edge of the board in the next shot. They are the second and third pads from the right. Missing from this shot is the 0.1uF capacitor that couples the audio to the next stage. There is also one extra capacitor that was part of a mod I later uninstalled. I’m showing you these shots to give you the overall idea of layout, what it looks like, and because it’s fun looking at circuit boards. For absolute accuracy of the circuit, follow the schematic –

The next 2 shots are the same board, but at an earlier point when I was using 1uF caps for interstage coupling. They are the 2 blue box-like caps. They didn’t make it to the final version of the board –

Here’s a wider view of the underside of the chassis at this stage of the construction, showing the main RF board wired to the octal tube socket, as well as the AF output stage with 4KHz filter, the 3KHz and 6KHz filter board on top of it, and the 2.4KHz filter board sitting on it’s own for the time being –

A closer view from a slightly different angle. At this point, it was beginning to dawn on me that keeping all this wiring tidy would take a bit more work than I had anticipated. I never did get the wiring as tidy as I wanted, but it’ll do –

This one’s a bit boring. It’s the “straight-through” real-pole LPF with a cut-off frequency of 20KHz, shown installed in the chassis on top of the 2.4KHz LPF –

and the 700Hz CW low-pass filter –

Here are all those filter boards stacked on top of each other. Looking at the left-hand stack first, from the top down is the 700Hz filter, the 20KHz “straight-through” filter and, at the bottom, the 2.4KHz sharp roll-off filter. On the right-hand side is the 3KHz and 6KHz filter board, with the 4KHz filter and AF output stage board on the bottom. You can also see the 6-position rotary switch that selects between the different filters. I had no trouble finding a 6-position switch with 2 poles but when I decided to also switch the +ve supply line to the filters, finding one with more than 2 poles proved tricky. I finally found it from a supplier of parts for musical instruments. It is distributed by AllParts, and is part number EP-0920-000. It is a 6-position 4-pole switch (one pole goes unused). Prices vary a bit, so search around for the best deal if you want this particular switch. If you want fewer filters, then you’ll probably find it easier to locate a switch that has 3 or 4 poles and 4 positions or less. This is the finished receiver, by the way. Well, finished for the time being – until I decide I just have to modify something –

Some more views of the underside of the finished receiver. You’ll notice that I designed a rear panel too. That also came from Front Panel Express – a more detailed view of it is coming later. The speaker is an 8 ohm, 4 inch, 6 watt unit made by CUI, model # GF1004. I got it from Digi-Key, part # GF1004-ND. Before finding this speaker, I purchased one from a company well-known for supplying vintage radio parts. It turned out to be very lightweight, with a small magnet, and generally rather disappointing. I liked the speaker I used in The Sproutie, so got the 4″ version of that one instead (the one in my Sproutie is a 3″ version). The aluminum speaker grille was custom cut by speakerworks.com

Coils were constructed in the same fashion as the coils for The Sproutie. In fact, the pinouts used on the octal socket are the same, so my Sproutie coils work in the Sproutie MK II, though they cover a wider range, due to the greater maximum capacitance of the tuning capacitor I used – a 2 x 50pF instead of the 2 x 35pF used in the original Sproutie. I decided to wind a complete set of new coils for this receiver. As of writing this post, I have 6 coils wound with a few more to go, as needs and desires dictate.

With The Sproutie, I used nylon hardware to secure the larger T68-6 toroids for the lower frequency bands. On the higher frequency bands, I used T50-7 toroids, and secured them with hot glue. This time around, I found that hot glue worked perfectly well for securing the T68-6 toroid cores too, so I used that technique exclusively. It’s faster and easier than using nylon nuts, washers and bolts. I didn’t think it would be the case, but if you need to re-make a coil, you can peel/break the glue off and re-use a tube base. In fact both the coils in the photos below were made with bases that were used at least once before –

I like these ceramic bases, because they are just a little higher than the phenolic ones, offering a bit more protection to the toroid. Wherever you get yours from, if they’re ceramic, they may well be the same ones as these, as most of these bases and sockets seem to be made in China these days –

“Take us to your leader”

You’ll need to figure out the exact details of your coils with the help of online calculators (I like the ones on W8DIZ’ site) and good old trial and error, but here are my details – they should give you a start. Remember to take into account the values of main and fine tuning capacitors, if they are different from mine – and the value of that 39pF capacitor between the tank and the base of the oscillator transistor, if you try a different value. I’ll update this table as I wind more coils. The plan is to wind general coverage coils up to about 21MHz or so, and a few more coils for specific bands. It is much easier, with the aid of the dial calibration graphs, to pinpoint exactly which 5KHz channel you are on, when the band coverage is limited to 1MHz or less. With the 20:1 reduction ratio of this National HRO drive, and the large, relatively massive dial, I found it quite easy to tune in stations even on the 13500-18300KHz coil, which spans almost 5MHz. For pinpointing which 5KHz “channel” I am on though, a general coverage receiver to listen to the oscillator of The Sproutie is more reliable (and faster) than reading dial calibration graphs.

For dial calibration, I use a piece of freeware called Graph. You won’t be able to read the following graph, as it’s a bit small. The original is a bit larger, and the software has an option for zooming in on a particular area of the graph. This is the dial calibration graph (so far) for my 5475-8450KHz coil –

I guess it’s time to do a reveal and show you what this little feller looks like from the front. You wouldn’t think it, but I spent a great deal of time on the front panel, figuring out the exact placement of all controls, placement of the lettering, and fonts. I was looking for a specific type of vintage knob for the RF gain, filter, and AF gain controls, but didn’t find any in good condition while building the receiver. Then I found some knobs on clearance at my local Radio Shack. Those are brand new RS knobs, but I think they look good and fit in well with everything else on the front panel. My main concern was to not “overdo it”. When sitting at the computer with the Front Panel Designer software running, it’s quite tempting to go overboard on the lettering, or try a colored panel, and colored letters in a fancy font. Just because you can do something though, doesn’t mean you should, and I wanted a front panel that was understated, functional, and that would still look good, regardless of how my personal aesthetic might change. Minimalism is the key, though the one extravagance I did allow myself was the larger “Sproutie MK II” declaration, and my callsign. I did try my callsign in red but decided that it looked gaudy. Best to play it safe, I think. I was also concerned that the finish might be a bit too shiny or glossy, but it turned out to be matt with a slight sheen. I’m very happy with how this looks –

Although the regen and fine tuning knobs, and escutcheon plates look the same, the ones on the right are attached to a National “Velvet Vernier” 5:1 reduction drive, via a fairly long coupling shaft. The knob on the left is connected to the 10-turn regen pot (via a 3/16″ to 1/4″ shaft coupler), while the black escutcheon plate is spaced away from the front panel by washers, and attached to it in a fixed position with 4-40 hardware –

Here’s The Sproutie MK II with her little sister, for size comparison –

A quick word about that regen control. On first installing the main RF board, one filter, and the AF amp into the chassis, I noticed that occasionally, when receiving a strong carrier, I’d hear a ringing in the speaker. My first thought was that it was microphonics caused by physical feedback between the internal speaker, which was bolted to the chassis, and some part of the circuit. Plugging in headphones didn’t cause it to go away, however. Undeterred, I continued building, and it was only after finishing the whole receiver, that I realized what was going on. I discovered that if I hear a ringing, all I have to do it back off the regeneration control a bit, and it disappears. I think this ringing is due to the high Q of the circuit when set right at the threshold of oscillation. If you recall Dan N7VE’s presentation on filters that I referenced earlier, he talks about how ringing in filters is caused by abrupt phase changes at the edges of the passband. The cure, when designing them, is to limit the Q in any one stage. Similarly, if you experience ringing in your regen, backing away from the critical threshold of oscillation will lower the Q of the circuit, and should solve the problem. Fascinating. I’ll be interested to hear if any other regen operators have experienced this. My guess is this would be less likely to happen in a regen that utilizes a bipolar transistor for the detector (or combined oscillator/detector if it’s just one device, unlike this design).

I had to try a shot from a lower angle, for that authoritative look. When I’m spinning that big old dial and listening to CW, I can almost kid myself that I’m intercepting enemy broadcasts for the valiant code-breakers at Bletchley Park.  In reality, I’m usually just listening to some ham tell some other ham what the weather is like at his QTH! –

The rear panel (thanks again, Front Panel Express) –

I like this receiver as it is, with the partially open chassis. From using The Sproutie, I have become used to seeing the vanes of the variable capacitor rotate as I tune the band, and I like that. I like seeing these vintage radio parts in action. However, I did learn from The Sproutie that whatever isn’t covered picks up dust – and when you’re living with 3 cats, 2 of whom are long-haired, a lot of cat hair too. I designed this receiver so that it would fit any standard 19″ enclosure that is also 6RU (rack units) or more high. The first plan was to make use of a hack (as the kids call it) of an IKEA product to make a low-cost rack cabinet. The IKEA Rast nightstand is the right size, and only costs US$14.99. For that, and the cost of a pair of rack strips, you can have a rack cabinet that is either 6RU or 8RU high, depending on how you construct it. A Google search on “IKEA Rast rack cabinet” or similar will yield a lot of sites and info on how to do this useful mod.

That was my plan for this receiver until I came across nice-racks.com.  David Tatelbaum makes beautiful studio racks out of his workshop in Massachusetts. He uses furniture-grade pine, though he will use other woods if you request them. The mahogany racks look gorgeous (but they do cost a bit more, of course). From his website –

“Nice-Racks are constructed of solid Pine furniture-grade panels…not just pressed wood or particle board covered in a laminate like some studio racks, but 100% real wood. The panels are cut to size and the components joined together securely using pocket-hole construction and self-tapping pocket-hole screws. The front sides and top edges are rounded, then the racks are sanded and stained. The finish is a clear matte enamel, scuff sanded between coats, to preserve the look and feel of real wood. Finally, hardware is installed and the fully assembled rack is boxed up and shipped out to its new home.”

After finding his site, I was hooked.  Yes, it was going to cost more than the cheap IKEA hack but at some point during the design and construction of this regen, I decided that I wanted it to look really nice, and expense was going to be a secondary concern. I was going full-hog on this. Besides, it took me over 6 months to plan and put together and spreading the cost over that time, the cost per month for my hobby was actually quite reasonable – especially if I take into account all those movies and dinners I didn’t go to because I was at home building! Incidentally, David’s racks are most definitely not expensive. When you consider the cost of your standard rack cabinet – the ones you find in music stores that are made of heavy particle board and covered in black veneer, his racks compare in price very favorably – and they are vastly nicer. They’re not ideal for the rough life of touring but for a home studio, they are perfect – and very good-looking.

OK, so time for the big reveal. This rack cabinet makes The Sproutie MK II look so great –

David also fitted rack rails to the top half of the cabinet at the rear, and supplied a 3RU-high steel panel to help enclose the receiver, and hopefully keep the cat hair away. On the left interior side you can see the recesses for the self-tapping pocket-hole screws that hold the whole cabinet together –

And in case anyone ever wonders who made this fantastic cabinet for my regen, David left his mark. What a quality job! –

The National HRO gear box does have a small amount of backlash – even when I apply as much tension to the anti-backlash gear as my poor little fingers can manage. At first, the backlash was something like 1 – 1 1/2 dial divisions. After increasing the tension on the anti-backlash gear as much as I could reasonably easily manage without the use of tools, the backlash, though still there, decreased to about 1/2 a dial division. It is a small amount, and also predictable, so not really a problem. For the purposes of dial calibration, I always turn the dial in the direction of increasing frequency before taking a dial reading. This ensures consistency in the readings.

Some videos of The Sproutie MK II in action. In the first one, the  towels are on top because Sproutie, my 3 1/2 year-old kitty (aka Sprat The QRP Cat) likes to sit on top of it, and I don’t want her claws to do to the wood what they have already done to my leather sofa –

The Sproutie MK II on 49M, 41M and 40M (though mainly 49M) –

There are some more videos of the Sproutie MK II, showing how a regen can be used in exalted carrier mode to enhance reception of weak AM stations, and on the 25M band, in this slightly more recent post.

There are a couple of things about my Sproutie MK II build that I’d like to change. The first is that, especially at the higher frequencies, the set is slightly sensitive to physical shock. A knock on the cabinet will shift the frequency slightly. I don’t recall noticing this effect with the original Sproutie, although to be fair, I didn’t do as much listening to SSB and CW with it as I do with the new receiver. I think one reason for this slight frequency shift may be the fact that the thick wires connecting the 2 stators of the main tuning capacitor to the coil socket are longer than in the original Sproutie. Although the effect is only slight, it is there, and that bugs me. It may also have to do with the much larger chassis, meaning more metal in the vicinity of a tuned circuit, that flexes when a physical shock is applied. The more I think about it, the more I think this second factor is the main reason. In practice, it is not a problem, but it is there, and I’d like to reduce it, if not eliminate it completely. Fixing a bottom plate to the chassis may help in this regard. Incidentally, banging the desk on which the Sproutie MK II is sitting has no effect. The rubber feet probably help a lot.

The above phenomenon is responsible for an interesting ringing effect that happens occasionally when the regen is set close to the critical point for receiving AM. It only happens with the internal speaker, so is being caused by sound from the speaker vibrating the main chassis. I did mount the internal speaker on small grommets, but this didn’t cure the issue. I have been looking for a reason to purchase a Palstar SP-30B external speaker, and this may be it! This is what the ringing effect sounds like –

The second thing is that, because the cabinet is wood, the receiver is not completely shielded. This would be useful were I to wind a coil for the 2-3MHz region and use The Sproutie MK II in conjunction with crystal-controlled converters to cover specific bands. This is a Regenorodyne approach, like Gary WD4NKA’s inspiring Regenerodyne receiver here. It would also be nice to reduce the possibility of picking up very local QRM in the shack. I could achieve better shielding with my Sproutie MK II by either simply housing it in an all-metal rack cabinet, or by cladding the interior of the existing wooden rack cabinet with thin metal plate or mesh. There is absolutely no hand-capacitance effect when using the set, due to the metal front panel, but when my cat Sprout jumps up on top of it (as she often does) the frequency shifts by about 20Hz. This is also due to the lack of shielding on top of the set. Again, it is not much, but it is there.

Sproutie (aka Sprat The QRP Cat) and The Sproutie MK II. Her contribution to the dial calibration of this receiver was carefully knocking the plug-in coils off the top of the receiver and watching them hit the floor.

August 14, 2015

A Sproutie is Born in France, to Henri F6GMQ!

Filed under: Amateur Radio,Ham Radio — AA7EE @ 12:10 pm
Tags: , ,

Around the same time I heard from Andy M6YAO that he had finished his Sproutie, I heard from Henri F6GMQ, who was also building a Sproutie and close to completion. A Sproutie in Orsay, in the North of France – how inspiring! To my knowledge, there are now 3 Sprouties in existence – Henri and Andy came in joint second.

Henri built his regen in an old measuring instrument case. He kept the original 12V power supply, for powering the circuit. The variable capacitor came from an old tube radio. He’s already thinking of constructing a second one, in a nice wood or aluminum enclosure. Love those instrument handles!

A view from the back, showing the side braces that help to make the structure more solid. We must be thinking alike Henri, as my most recent version of The Sproutie also has instrument handles and side braces –

Henri’s first coil gives coverage from 5.5 – 7.2MHz. He says he has been able to listen to SSB, CW and broadcast stations and that selectivity and sensitivity are great, considering the relative simplicity of the circuit –

It’s interesting to see how other people build things. It looks as if Henri made his own Manhattan pads. Nice job! He also mentioned that he likes the AF stages of this receiver. Our thanks go to Charles Kitchin N1TEV for that, as they are the AF stages from the regen he described in the Feb 2010 issue of CQ magazine. Henri said that the receiver behaves exactly as I described. I do try to accurately reflect my experiences, so thank you for mentioning that Henri. I don’t think there’s any point in covering things up. If I think there’s a potential issue, I’ll mention it so you, the reader, will know what to expect.

Henri is looking for ideas for a simple 40M VFO, as 40M is his favorite band. He is thinking of building a high performance receiver for 40. If anyone has any ideas, you can leave comments underneath so that Henri will see them. He’ll be very grateful, and interested in all ideas, I’m sure.

Thank you very much for sending your photos Henri. It’s really great seeing how others build things, and it’s really great to know that there are now Sprouties in the US, the UK, and also France. Also, a big thank you to all who were involved in designing the circuit elements that make up this cool little receiver. They include (but are not limited to) GI3XZM, GM4HTU, G3RJT, G3VMU, G4RGN, VK2BHT, G3RJV, and N1TEV.

August 8, 2015

Andy M6YAO Builds A Sproutie!

Andy and I have been communicating via e-mail since April. He is M6YAO now but back in April, he was plain old unlicensed Andy, who was about to apply for his Foundation License in the UK. He had built a Mark regen from Walford Electronics, which seems to have given him a taste for regens. He mentioned that it was a good receiver and worked well but that the tuning, accomplished by a polyvaricon with no reduction drive, was a bit critical, so he was looking for a regen to build that represented “the next step”, so to speak. It turned out that The Sproutie was that next regen for him.

I haven’t built any of the currently available regen kits but The Mark from Walford Electronics, and The Scout from QRPKits both strike me as good ones for anyone who has never built a regen, and wants to get their feet wet. However, when you’re ready for more, there’s nothing like a quality air-spaced variable capacitor and a nice solid reduction drive with calibrated dial to make you feel like you’re navigating the airwaves in style. In my secret (and perfect) world, there is a kit version of a regen with a pre-drilled and engraved, large and stout aluminum chassis, top quality air-spaced variable capacitors and reduction drives, and a variety of accessories (wooden enclosure, extra formers for adding bands, etc). Also, in my perfect world, this kit wouldn’t cost the many hundreds of dollars it would need to in the real world we all live in. If anyone were admirably eccentric enough to produce such a kit, I think that very few would actually buy it, due to the high cost.

Andy and I continued to e-mail each other, as his Sproutie gradually took shape. It was really interesting viewing the progression of his project as he encountered challenges, experienced setbacks, asked questions and one by one, solved his problems. It was a process that all home-brewers will recognize from their own pursuits, and a pleasure to observe. We have all had the kind of projects that present issues we are unable (or unwilling) to solve, so it is a fantastic feeling of achievement when projects succeed despite the obstacles that occur along the way. I get as much of a kick out of others’ successes as from my own – especially when it’s with a receiver like The Sproutie that is rather dear to me.

Incidentally, in the UK, when upgrading from a Foundation to an Intermediate license, there is a practical element to the requirements. Andy wanted to use his build of The Sproutie to qualify. The RSGB website says, “First, a practical skills assessment is taken which demonstrates your competence in basic electronics. This involves soldering a rudimentary circuit together using some of the components you learned about on the course.” A successful Sproutie build would seem to more than fulfill these requirements.

Bit by bit, Andy sourced the parts from various sources, including some from the US. He ended up with more reduction drives than he needed, and had to decide which one to use. He also incorporated a DC ripple filter from VE7BPO’s blog (I’m not sure if that became part of his final build). As the receiver slowly began to take shape, he was still deciding what to use for an enclosure. Whenever we build something, we make multiple decisions along the way, and it was interesting to follow along as Andy went through this process. I’m not sure if he experienced this, but I sometimes find that the plethora of decisions to be made really slows me down. Planning a project is a bit like playing a game of chess, as a decision you make now will affect many other moves in the future.

Although the AF amp board worked, on connecting all the boards together for the first power-up of the complete receiver, Andy was greeted by – a big nothing. We’ve all been through that and it can be somewhat dispiriting, but this is where our valiant builder’s homebrew mojo really kicked in, and he earned his stripes. He checked a lot of things, which all seemed to be in order, but didn’t give up. Finally, one afternoon, I received an e-mail that was titled “Eureka moment”. It turned out that his RF board was connected to the +ve supply line, but not to the ground. This is one of those “How on earth did I miss that?” moments that anyone who has ever built anything will know all about. Andy did experience a few more issues as he cased the set up but as they arose, he dealt with them. He said, ” I have learnt lots and I think it will help me in other projects I undertake in the future. ”

He used a metal file case for an enclosure, and the main tuning dial and drive is a NOS (New Old Stock) Muirhead Type C, with a 50:1 reduction ratio. 50:1 is huge – you must have fantastic slow tuning Andy –

Andy reports that it works well, fills the room with sound, and the bass boost works too. Because the file cabinet has a lid with a latch, he stores the unused coils inside the lid, held by spring tool clips. The plate on the top will have a legend, indicating the frequency ranges that the various coils cover –

Andy also owned a Tecsun PL-880 but he says that compared to The Sproutie, it seemed sterile. He writes, “The Sproutie seems to live and breathe in comparison and requires user interaction instead of just punching in a number through a keypad. ” He recently sold the Tecsun because, in his opinion, although it was probably technically better, it didn’t provide the same user experience as his new regen. A convert! This is exactly how I feel about direct conversion receivers and (particularly) regens. The simple circuit architecture leads to a relatively unprocessed sound and makes me feel as if I’m in more direct contact with the airwaves (or perhaps it’s just the lack of AGC!) It’s very affirming to hear the same sentiment voiced by someone who is a relative newcomer to these intriguing receivers.

Andy will be taking the exam in October to upgrade from his Foundation license to an Intermediate license. He already submitted his Sproutie build as the “simple” radio project part of his exam and of course, it passed.

Congratulations Andy, and thank you for sharing your Sproutie build with us!

April 12, 2015

New Solid State Regen Discussion Group

Filed under: Amateur Radio,homebrew radio — AA7EE @ 6:06 pm
Tags: ,

I had meant to tell you about the new online discussion group for regen builders in the last post, but it slipped my mind. Sometimes, when writing blog-posts, my big concern is to get it finished, so I can put it behind me and move on to the next new, interesting thing. In the midst of the push to do this, things sometimes get forgotten.

The bright side is that now, this subject gets it’s own post, and may get a little more attention as a result. Professor Vasily Ivanenko of Popcorn QRP fame, has started a new regen discussion group on Google+, designed specifically for discussion of solid state regens, You can find it here. Not too many members yet, but it’s very new. There’s a good discussion group on Yahoo Groups, called RegenRX, which tends towards discussion of tube designs (though solid state is discussed there also). I used to really enjoy Yahoo Groups, but have never been able to make peace with the newer interface. I think it’s less user friendly, and my visits are limited as a result. There is also discussion of regens, as well as other simple receivers, on The Radio Board, run by Dave Schmarder N2DS and Jim Kearman KR1S.  It’s a discussion board with a classic and uncomplicated interface. Nice and clean looking, no drama, very agreeable, and full of good information and communication, as well as an attentive and dutiful moderator.

I tend not to participate a great deal in online discussion groups, preferring to make a few posts, then duck out and leave everyone else to it. However, I couldn’t resist joining this one. I hope you will too.

April 8, 2015

Holy Grail Attained – A National HRO NPW Gear Drive and Dial in FB Condition

Firstly, I must apologize for posting so many pictures of these National HRO gear drives and dials. Once I decided that a building a regen with one of these dials and drives as the centerpiece was a goal, it became something of a preoccupation to find both a dial and drive that were just right. Luckily, I have now found that perfect combination, and can promise that this will be the last post on the subject :-)

An idea that has been brewing in the back of my head was to write a post on the subject of dials and reduction drives. I have purchased and looked at a number of different types over the last year or so, found a few to be slightly lacking, and others to be eminently suitable, for the purpose of tuning a home-built radio receiver. For a number of reasons (that I may go into in a future post one day), I consider the National HRO micrometer dial and gear drive to be one of the best solutions. Luckily, there are still quite a few of them knocking around, for the builder who is willing to spend a little time looking for just the right one.

When I saw this particular drive on eBay, I knew I had to have it, at almost any price (within reason). Firstly, the gear drive was in nice physical condition. Also, it had a feature I had not seen before. Although I have been aware of these drives since my teenage years, I have only been paying close attention to them in the last few months. Perhaps this is not that unusual, but it stood out to me – there was an extra feature on the front of this drive, in the form of a shaft rotation limiter. It is an ingenious mechanical device that will not allow the dial to rotate more than 10 turns in either direction. The rignt-angle drives have end-stops built into the inside of the top cap of the gear box, but the standard straight-through models have no such rotational limits.  The variable capacitor I have been planning to use with this next project does not have end stops, so to have one built-in to the drive would be great. The fact that this drive looked to be in really good condition as well (judging by the photos online) elevated it to “must have” status.

A week or two later, this little beauty was in my hands. These are the “before” pictures, so if you look at these, make sure to stick with me to the end of the post to see how things turned out. Having said that, it looked pretty darned good from the get-go though. Although you can’t really see how the shaft rotation limiter works, you can see it’s component parts that are stacked over each other on the tuning shaft, in between the metal end plate and the cast metal gear box –

On removing the top cap, I was expecting to see a moderate amount of partially dried grease on the various component parts of this drive. What I found instead was a large amount of grease, applied in generous dollops. I wonder if there had been a special directive to apply a lot of grease in order to protect this batch against an extreme climate, ot perhaps it was just down to the whimsy of the worker who had been applying the grease to these gearboxes?

Look at all that grease! You can’t see it. but there were some very large dollops underneath the gears, in the interior of the gearbox –

Before dousing the gearbox with WD-40 and then dish soap, I removed as much of the grease as possible with a toothpick, before partially disassembling it. Then I went to town on the gearbox and all the parts, with generous amounts of WD-40, a toothbrush, then dish soap and the toothbrush, followed by nice long soaks in warm dish-soapy water (and the toothbrush again). Then came a good rinse in non-soapy water, and plenty of attention from a hairdryer on the hot setting to dry it all out.

Look at the squeaky-clean result. It just amazed me, looking at this, to realize that it was something like 70 years old, and it has plenty of life left in it still –

All the parts were now clean, dry, and ready for reassembly. It is not my intent to give detailed how-to instructions here. If you read my previous posts about these drives, as well as the other supporting information online that I have linked to in the previous posts, you’ll know enough to figure things out – especially once you’ve looked at one in real life.  Although these straight-through gearboxes have more parts than the right-angle drives, they are easier to figure out. In the following shot, you can see the slip-on washers of the shaft rotation limiter that fit over the tuning shaft. Each washer has a tab with a small protrusion that prevents it from slipping over the collar next to it. There are 11 of these tabbed washers in all –

The plastic lid under the loose parts once held fruit salad from Genova Delicatessen. If you visit Oakland, CA and like East coast style deli’s, Genova’s on Telegraph and 51st is a must!

Remember to set the anti-backlash setting on the gear that is spring-loaded, before inserting the tuning spindle into the gear box. Do not over-tension it, or there will be too much friction when tuning. All you need is just enough tension to counter the backlash and no more. The sprung gear only needs to be offset by one, or two cog-teeth at the most.

Next came the lubrication stage. There needs to be grease in every place where there is metal moving over metal. The shaft rotation limiter with it’s 11 tabbed washers added a fair bit of drag, even when coated with a thin film of grease, so I squibbed a small amount of turbine oil in between each washer. While doing this, I was wondering about mixing turbine oil in with the synthetic grease. So far, it has seemed to work fine. If there are any problems in the future, it would not be hard to remove just the front plate and the washers, so they can be cleaned and re-lubricated. At this point, I am almost looking for excuses to do things like that!

This is such a good-looking gear drive. I almost can’t believe that it is something like 70 years old.  If you look closely at the 4 screws (of which you can see 3 in the following picture) holding the eccentric hub flange to the front plate, and compare with the very first picture in this blog, you’ll see that I have carefully filed them down. I did this in order to maximize clearance with the back of the micrometer dial. I am planning on using a 4mm front panel in my next regen, and need all the clearance I can get –

The dial that came with this particular drive was in good shape. However, I already had one that was in even nicer condition. This particular combination of dial and drive are the best in my small collection. They have made the cut, and with the 20:1 reduction ratio and nice heavy dial, will make a grand main tuning dial for a homebrew receiver –

April 7, 2015

The National HRO NPW Dial and Gear Drive

The gradual (and selective) acquisition of vintage radio parts here continues, as I hone in on the perfect tuning dial and drive for my next regen, I’ve been wanting to find a really nice National HRO Micrometer dial and drive for the purpose, and have finally found it.  I had to purchase 4 dials and 3 drives to get exactly what I wanted though.

As well as selling their gear drives with built-in variable capacitors, National also sold the stand-alone PW and NPW drives which could, with the use of a shaft coupler, be used to drive any variable capacitor the builder desired. The PW drive, in which the drive shaft ran Parallel With the front panel, was also known as a right-angle drive, as the drive shaft came out of the gear box at right angles to the tuning shaft. The drive shaft of the NPW drive was Not Parallel With the front panel, and was also known as a straight-through drive, as the tuning shaft and drive shaft were in the same plane. For many builders, myself included, the PW drive is not ideal, as the variable capacitor would tend to get in the way of the other front panel controls and parts. On the other hand, with the NPW drive, the main tuning capacitor sits directly behind the gear drive, leaving room either side of it for the other front panel variable capacitors, potentiometers, switches etc. From the National Radio Products catalog for 1947 –

The NPW drive was my holy grail, and I set about watching eBay for one. The first such acquisition was listed thus, “has dings,scratches and scuffs – knob has spring and turns, gear turns properly”. The dial had definitely seen better days and although the gear box did look to be a little scuffed, I figured that it was most likely in good working order, and would only need a through cleaning and re-lubrication to put it in working shape for the next few decades. I paid a little more than I wanted to for it but darnit – I wanted it, and was pleasantly surprised when it arrived to find that it was in fair condition. I haven’t pictured the dial, because it was in pretty rough shape but that was of little concern, as I already had a very nice dial. It was the gearbox I was looking for. This one didn’t end up quite making the cut for my next regen, but it came close. These photos are the way it was on arrival, before I cleaned and lubricated it –

The grease was old and although the gears did turn smoothly, I couldn’t help wondering if they’d turn a little smoother with a complete cleaning and re-greasing. The grease was getting a bit dried up, and it was time for this gearbox to receive some TLC –

I wasn’t able to find as much online documentation on this gear drive as on the right-angle drive (the one that uses a worm gear). This makes sense, as the National HRO receivers used right-angle drives – there seem to be more of them floating around than these “straight-through” drives. The only place I found any info on the NPW drives was here. However, after disassembling and lubricating a right-angle drive, this one was easy to figure out. It has more moving parts, but is a very simple arrangement. You may not be able to figure it out from looking at these photos but if you see one in real life, after turning the shafts and seeing the gears turn, it’s operation becomes very clear –

You can’t see the eccentric nature of the hub too well in this picture. I probably didn’t capture it from exactly the correct angle. However, you can see that it had been removed and replaced upside down. Note how the word “top” is at the bottom. This was probably so that the gear drive could be positioned upside down in it’s previous installation (whatever that was) –

Time to take it apart, and thoroughly clean all the old grease off. This was achieved with an old toothbrush, many squibs of WD40, then a great deal of dish soap, scrubbing all the time with the toothbrush, before rinsing and drying. A hairdryer at maximum heat helped the drying process. It was surprising how hot the metal casting became after a minute or two under the hairdryer. Here’s the fully cleaned and dried gear box, before re-assembly, I didn’t remove the gear that was attached to the drive shaft, though this would have been quite easy –

Two closer views of the eccentric hub with the spindle and 2 fiber washers –

The cleaned and re-assembled gear box, before re-lubrication. It’s not too clear in this photo, but the gear on the right is tensioned with a spring to eliminate backlash. You can see the spiral spring near the center of the gear. When re-inserting the tuning spindle, you should use your fingers to tension the gear by just one or two teeth before engaging the tuning spindle. If you tension this gear too much, there will be too much resistance when you try to turn the tuning knob. All you want is enough tension to eliminate the backlash and no more –

A view of the cleaned gearbox from above. What a difference!

And the gearbox cleaned and assembled, but not lubricated (it will have to be partially disassembled in order to be lubricated) –

For lubrication, I use Mobil 1 synthetic grease, applied with a small (1 ml) pipette (the type used to administer medicines to pets), a toothpick and at times, my fingers. After applying sparingly, I turn the gears to distribute the grease and with the toothpick, remove any surplus. Once any grease has been pushed out of the gear teeth and to the side, it’s never coming back,so why keep it around? Grease should be applied in every place where metal moves in contact with metal, but you don’t need a lot. This includes the inside of the eccentric hub, through which the tuning spindle passes (the spindle that is connected to the dial), as well as the outer part of the hub, which comes into contact with the micrometer dial –

In the following view, the anti-backlash spring on the left-hand gear is visible. You can see one end of the spring poking through a hole in the gear, and the other end held in place by a collar around the spline –

Here’s a final view of the assembled and lubricated gearbox. I forgot to install the 4 screws on the top cap but other than that, it’s complete, and ready for many more years of service –

The dial that came with this gearbox has seen better days. Although I have certainly seen gear drives of this type in better external shape, this one does operate smoothly.  You can spin the dial and it continues spinning for a turn or two, even with a variable capacitor attached. Not long after cleaning up this drive, I found another one in particularly nice condition, which will be the main tuning control for my next regen. I’ll  show you that drive in the next post. In the meantime, this one will go on the shelf in a box, waiting for the right future project to come along.

April 3, 2015

An Early Morning Spin On 49M With The Sproutie

This morning, my 2 eldest kitties did a real number on me. The senior was the first. At about 5am, she sat on her food shelf (one of 3 shelves mounted on the wall next to my bed, specifically for the cats to hang out on), next to her empty food bowl and began meowing loudly, while fixing me with an innocent gaze. I was able to ignore this for a good 20 minutes until the next eldest, my blind cat Jingles, jumped up on the bed and also began a “feed me” campaign, which consisted of vigorously rubbing her little furry head against my face. The combined effect of both initiatives was too much to easily ignore so as soon as I had fed them, I found myself sitting in front of The Sproutie and thinking that I might as well make use of the fact that I was up at 5:30am, while night-time and grey-line propagation on 49M would be in full swing.

The choice of 49M for this listening session was simply because it was the coil that was plugged in. I listen to Radio Habana Cuba most nights on 6165 and 6100KHz. The 6165KHz signal, which comes online at 6pm local (0100z) has been rather weak recently, but the signal on 6100KHz from 10pm-midnite (0500-0700z) is a powerhouse. I sometimes record the 6100KHz signal but am quite often foiled in my attempts to catch the penultimate hour of programming, due to RHC’s various foibles. Last night, the carrier appeared on 6100KHz at 4 mins after the hour, followed a further 5 mins later by the audio. My plans to record the 1-hour program in English were thus foiled and by the time it was repeated at 11pm local, I was feeling too sleepy to last the whole hour.

When going to bed, I usually leave The Sproutie on 6100KHz so that I can awake to the sounds of KCBS Pyongyang on the same frequency. It is mainly music, with occasional spoken word in Korean. I hear many of the same tunes during their morning programming, and there is great theater of the mind in hearing their slightly kitschy melodies interspersed with the impassioned-sounding commentary in Korean. I hear the same melodies most mornings, and there is a certain appeal to this somewhat exotic “sameness”. I can imagine the members of the elite in Pyongyang waking up to this kind of “inspirational” programming every morning.

Coffee at the ready, I decided to perform a band scan on 49M with The Sproutie. The idea was to log every station I could hear on the band. The excellent site short-wave.info made it possible to quickly ID most stations, before moving on to the next. I didn’t linger for too long on any one frequency, as the goal was to get an overall idea of band activity, rather than to positively ID every single station heard.

Needless to say, I heard a lot of Chinese :-)  Here’s what The Sproutie and I came up with –

 Freq  Station  Language  UTC
 5830  WTWW  English  1342
 5875  BBC  English  1343
 5915  CRI  Mongolian  1347
 5925  CNR 5  Chinese
 5935  PBS_Xizang  Chinese
 5955  CRI  English  1354
 5975  CNR 8  Korean  1356
 5990  PBS_Qinghai  Tibetan  1358
 6015  North_Korean_Jamming with un-ID’ed station underneath  1401
 6030  CNR 1  Chinese  1404
 6055  Radio Nikkei  Japanese  1405
 6065  CNR 2  Chinese  1406
 6080  CNR 1  Music  1414
 6095  KBS World Radio  English  1415
 6100  KCBS Pyongyang  Korean  1417
 6105  Radio Taiwan International (jammed, but jamming not heard)  Chinese  1418
 6110  PBS Xizang  Tibetan  1420
 6125  CNR 1  Chinese  1422
 6135  North Korean Jamming (w/ music underneath)  1424
 6155  CNR 2  Chinese  1427
 6175  CNR 1  Chinese  1429
 6185  Unidentified station (possibly China Huayi BC. Corp  Music  1431
 6190  PBS Xinjiang  Mongolian
 6195  BBC (jammed, but jamming not heard)  English  1434
 6200  PBS Xizang (or Voice Of Jinling)  Chinese  1436
 6250  North Korean Jamming  1438
 6280  Xi Wang Zhi Sheng (just 100 watts!)  Chinese  1440
 6348  North_Korean_Jamming_with_station_underneath_(presumably_Echo_Of_Hope)  1447

Lots of stations – and loud too, For the majority of the listening session, I had the RF gain on the little Sproutie cranked down to 1/2 or 1 on a 1-10 scale. Another benefit of this band-scan was that I got to fill in a few more calibration points on the dial calibration graph for this coil. The details on this screen grab are a little hard to read but that’s fine, as your calibration graph would be different anyway. Just take a gander at that nice smooth curve though –

Anyway, that’s it. It is now about 9:30am and I am beginning to wish I hadn’t risen so early. However, I blame the cats, and the good side is that I got to take a whirl on 49M before first light. Don’t let anyone tell you that you can’t use a regenerative receiver for serious SWL’ing. If anyone says that their regen doesn’t cut it for SWL’ing, just tell them that it must be because they didn’t build it properly :-)

The Sproutie and a cuppa coffee kept me company early this morning throughout my sojourn on 49M.

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