The NA5N Desert Ratt 2 Regen

EDIT - If you’re thinking of building the Desert Ratt 2, although the pictures in this post are numerous and quite large, I do recommend reading all the text too, as I have included what I thought were relevant details on the construction as part of my narrative. Also make sure to read the comments and replies.  Previous blog-posts have taught me that readers often ask pertinent questions, so you may be able to glean a little more information from them too.  In fact, just before I wrote this, Paul NA5N made a comment which includes a usefiul piece of information about the 2 x 1,000pF (0.001uF) capacitors in the regen stage.

I’ve been wanting to build NA5N’s Desert Ratt regen ever since I first found his very attractively drawn schematic for it online. I then found the updated version, called the Desert Ratt 2, and a very good description of how the circuit works – all of these documents available on Paul’s website. What more could an avid regen builder want? Not much, it turned out. Late last year, when N2CX and N2APB dedicated an episode of Chat With The Designers to the Desert Ratt (and to the subject of regens in general), I just had to listen and of course, it fueled my interest in building the DR2 even more. The whiteboard for this particular episode of CWTD is here, and the podcast audio is here.

The WBR was a successful regen for me and while it worked well on SSB/CW, it didn’t seem to quite have the gain with AM stations. This makes sense, as a regenerative detector has to be set below the point of oscillation for AM reception, at which point it has less gain than when it is oscillating (which is where you set it for SSB/CW reception.)  Even so, I had read that bipolar transistors tend to work better as regen stages for AM, as they have higher gain when not oscillating. The search was on for such a receiver, and this was one of the key deciding factors in building the DR2 for me. In fact, Paul has mentioned (I forget where I saw it, as I have done so much reading on this receiver) that the Desert Ratt doesn’t do so well with SSB/CW as it does with AM. My experience with it backs up this assertion, thought it’s a pretty neat receiver for AM.

In particular, I wanted a receiver for covering the 49M SW BC band as although my Elecraft K2 covers a few of the BC bands, 49M is not one of them. There were a few things I found interesting about the design. The use of a phase splitter transistor to convert the single-ended output of the detector to a balanced output in order to drive the LM386 in differential mode was novel. Paul talks about how much RF is flying around inside regen receivers, and how the common-mode rejection of the 386 when used in differential mode can be advantageous in such an environment. I was also intrigued by the detector consisting of 2 germanium diodes – I think I was just looking for an excuse to build something with Germanium diodes again to remind me of my crystal-set building days as a kid

If you look at the schematic of the DR2,  you’ll see that one of the changes in the design from the original DR is that instead of a variable capacitor, it uses 1N4004 diodes as varicaps. I have a bit of a “thing” for nice air-spaced variable capacitors, and I had in mind a nice Millen 50pF capacitor that I picked up on eBay for a very fair price last year. Combined with a 6:1 reduction drive, it made a good combination with a very useable tuning rate for tuning in AM stations.

Anyway, I’m getting ahead of myself here. I did make a few changes to the original schematic for my version, so allow me to introduce my rather wobbly circuit diagram -

The differences between my schematic and Paul’s are as follows -

- I added an RF attenuation pot at the antenna input. After building the DR2, I found that using a relatively short piece of wire indoors as an antenna was causing a lot of common-mode hum.  On top of that, I wanted to be able to increase the signal level into the receiver with the use of my regular outside antenna (A 40M dipole fed with 300 ohm balanced feeder.)  Using the attenuation pot allowed me to use the large outdoor antenna without overloading the receiver.  It also created enough separation between the receiver and antenna that the hum problem almost entirely disappeared.

- Earlier versions of the Desert Ratt included instructions for winding the coil on a plastic 35mm film canister and on an IC shipping tube. The DR2 schematic doesn’t include such instructions, but I wanted to use a toroid, so I experimented a bit and came up with a scheme that seems to work OK.  I used a T68-6 former and the turns info is on my schematic above – a T50-7 would take up a little less space. More about this later.

- I had a few 2-position center-off switches that I wanted to use, so I used one of these for a bandswitch instead of the SPST switch in NA5N’s DR2 schematic. I had originally thought that using the 50pF tuning capacitor with no padding would make the upper limit of frequency coverage too high, resulting in too large a frequency swing in one band, but there must have been more stray circuit capacitance than I had anticipated, as the coverage with no extra padding was about 7.3 – 13MHz. This band became the center position.

- I was attempting to power the DR2 from my shack power supply, which is about 45AH of sealed lead acid batteries with a float charger constantly connected.  This also powers my K2, and the DR2 was picking up processor noise from the K2, as well as a low-frequency “burbly” kind of noise of undetermined origin. The problem went away when I powered the receiver from a separate SLA. but I decided to add extra filtering to the power line anyway.  I found that a 1mH choke as well as a 1,000uF electrolytic almost (but not quite) got rid of the unwanted interference on the power line.  For good measure, I added a 0.01uF RF decoupling capacitor across the power line at the input connection.

- I added an AF preamp stage directly after the diode detector to ensure enough power to easily drive a speaker - even with weak signals.

- The inputs to the LM386 are the opposite way around from the way indicated in NA5N’s DR2 schematic.  With the inputs connected as shown in Paul’s diagram, the LM386 emitted a loud screeching sound.  Swapping the inputs cured this. I was not the only person who had this problem, as I discovered from this post in the GQRP Yahoo Group (you need to be a member of the group to read the post).

-  I left pin 7 unconnected. I don’t understand the way that NA5N has it connected to the junction of the series resistor and capacitor connected between pin 5 and ground in his diagram.  Most circuits that use pin 7 call for a decoupling capacitor direct from pin 7 to ground (usually about 10uF).  This helps reduce large signal distortion, though Paul does say that in this application, it may not do a great deal to help and is therefore optional.  I elected to leave it unconnected.

Now for some pictures.  I didn’t want to spend a lot of time constructing an enclosure, so decided to make a simple PCB L-shaped chassis and build the circuit directly onto that.  With the variable capacitor mounting bracket, it still ended up taking quite a while to construct though. All my projects begin like this, with the main components and control being laid out on the front panel, while deciding on the basic layout -

I’ll spare you the words at this point and apologize for all the pictures that are about to come. If you’re living in a remote area and are still relying on dial-up, then I feel a bit sheepish about the sheer number of images to follow!  I’ve talked before about constructing enclosures from PCB material, so won’t repeat that information here. As well as constructing the chassis from PCB material, I also made a mounting bracket for the variable capacitor and a tuning pointer to attach to the reduction drive with 2 small screws – all from double-sided copper-clad laminate.

I applied several thin coats of lacquer from an aerosol spray.  It was sprayed from a distance, resulting in a light, and stippled coating, which you can see in these pictures. I’d rather apply too light a coat than risk overdoing it. The downside of this is that oxidation will being to affect the appearance of the copper fairly soon. Oh well. The capacitor mounting bracket received a thicker coat. You can see the smoother, shinier finish.

I got the 6:1 reduction drive from Midnight Science. A number of others sell them, and one place that springs to mind is Mainline Electronics in the UK. They are the suppliers for Jackson Bros components (I think they have the rights to manufacture and sell the parts).  They sell on eBay using the name anonalouise.

The enclosure looked a little bit different by the time the DR2 was finished, as the hole for the nylon toroid mounting hardware hadn’t been drilled in the base at this point.

Look at that gorgeous variable capacitor!

A close-up view of the Millen 21050 50pF air-spaced variable capacitor and mounting bracket. This component is silver-plated (the vanes are probably brass), and has double bearings and a ceramic base. It is a very nice variable capacitor, and had never been soldered to before being used in this project. It is at least 35 years old – most likely older!

Boy, was I glad to finish the chassis so that I could start work on wiring it all up.  I decided to build the AF amp first and work backwards, my thinking being that the AF amp would be relatively straightforward. The act of touching the input with a metal screwdriver and hearing a hearty buzz in the loudspeaker would give a welcome psychological boost! If I started by building from the antenna end, I’d have to wait until the entire receiver was built before getting any clue as to whether it was working.

Here’s the chassis with the LM386 amp, the 2N3904 phase splitter, and the 2N3904 preamp built. As has been the case with all my projects since I started using then, I used W1REX’s wonderful MePADs and MeSQUAREs to build the circuit -

Here’s a close-up. The 2N3904 preamp is just below the 6:1 reduction drive, and the 2N3904 phase splitter is to the left of the LM386.  The 100uF capacitor that decouples the supply line to the LM386 straddles it. I read that it is best to ground it to pin 4 instead of to some other point on the chassis to avoid instability, hence the reason for this placement. The other electrolytic that is straddling the chip is the 10uF capacitor between pins 1 and 8 that sets it to the maximum gain of 46dB. The black shielded cable connecting the AF gain pot to the circuit on the PCB is lavalier mic cable.  It has 2 conductors, each of them in it’s own shield, which is ideal for wiring up potentiometers. It is fairly thin and very flexible. I use it in all my home-brew projects. I bought it from a local pro-audio store which recently closed down, so will now need to find another supplier.

In this view, you can clearly see the extra DC supply line filtering that I added, consisting of a 1mH choke in series with, and a 1,000uF electrolytic across, the DC supply. After seeing these pictures, I noticed that there wasn’t very much solder on the joint connecting the choke to the power jack, so I re-flowed the joint and melted a bit more solder onto it.

The power indicator LED’s main function is as a voltage regulator. NA5N marked the various voltages on his schematic for the DR2, and I chose an LED with a forward voltage drop to match those voltages as close as I could.  A green LED in a variety pack I got from Radio Shack had a forward voltage drop of 2.1V, which seemed about right.  The 1N4148 had a forward drop of about 0.65V.

The next stages to be built were the detector and impedance converter/buffer stages.  The description of the DR2 on NA5N’s site gives more info on these stages (as it does for the whole receiver). I couldn’t be sure these stages were working, but bringing my finger close to the diodes resulted in a pleasing cacophony of stations in the headphones – and at a louder level than in doing the same to subsequent stages, so I figured there was some detection/amplification going on

I didn’t know how many turns I was going to use on the toroid, but using the calculator on W8DIZ’ site and an online resonant frequency calculator, I figured that 36 turns on a T68-6 should be a good starting point for the whole winding from pin 3 to pin 6. In Paul’s version, with the coils wound “traditional style”, the tickler winding was about 1/3 of the whole winding.  Coupling between windings is tighter with a toroid than a “regular” coil, so I reduced the number of turns on the tickler. I found that regeneration was occuring at only about 25% rotation of the regen pot, so further reduced the number of turns. Using the turns shown on my schematic at the beginning of this post,  the regen stage moved into oscillation at anywhere between 40 and 50% rotation on the pot, so I left it at that. For the same reason of tight coupling, I used fewer turns on the antenna winding too and because I am using an outdoor antenna, could probably have used even fewer turns.

The toroid was fixed to the PCB with nylon nuts, bolts and washers that I got from my local Ace hardware store.

Here are some pictures of my Desert Ratt 2 with the circuit finished -

The red wires running along the back of the front panel are the regulated 2.1V and 2.75V lines.  I would have run them on the main board but ran out of room due to lack of planning, so went vertical.  Incidentally, although I refer to the 2 regulated lines as 2.1V and 2.75V,  the exact voltages aren’t important.  That’s just what they turned out to be in my case.

The RF amp and regen stages can benefit from transistors with high hfe. I got a cheap Harbor Freight DMM that measures hfe from an eBay vendor for under $6 including shipping.  hfe varies depending on the collector current, but I was doing this mainly for comparative purposes rather than absolute values, so the fact that I didn’t know what value of collector current was used to measure hfe in this cheap meter didn’t matter. It just so happened that my 2N2222A’s tended to have higher hfe than my 2N3904′s, so I ended up using a 2N2222A that measured in at hfe = 203 for the RF amp, and a 2N2222A with hfe = 223 for the regen stage.  The other stages don’t require high-gain transistors. NA5N talks about it in this post on QRP-L from 1999. Bear in mind that he was talking about the original version of the Desert Ratt in this post (just so you don’t get confused when he identifies the various transistors).

I did promise that I’d give a bit more detail on the toroid. Mine was wound on a T68-6 former. The main winding was 30 turns tapped at 27 turns from the top (3 turns from the bottom). The antenna coupling winding was 5 turns.  All turns are wound in the same direction. I used 26 gauge wire, but the precise gauge isn’t important. 26 gauge was narrow enough to easily fit all the turns on the former, yet stout enough to lend some stability to the oscillator, as the toroid isn’t sitting close to the board, and the leads are relatively long. When putting taps on coils, I used to not cut the wire i.e. I would simply make a loop in the wire, twist it, tin the twisted part and keep on winding.  Now I find it is easier to treat them as 2 separate windings connected together. If you can get heat-strippable wire, please do – it makes winding toroids so much easier and more pleasurable.  I wound the first winding of 27 turns, stripped and tinned the end, then stripped and tinned the end of another piece of wire, twisted and soldered them together, and carried on winding the last 3 turns in the same direction (this is important).  The separate antenna winding of 5 turns is also wound in the same direction.  I’m afraid I didn’t write down (or if I did, I have since lost it) the lengths of wire used. I did notice that the turns calculator on W8DIZ’ site (linked earlier in this post) was quoting lengths that are too short for the T68-6 former.  All you have to do is wind one turn around your former, measure that length, multiply it by the number of turns you’re going to wind, add an extra inch or two for the leads and, as we say in England, Bob’s yer Uncle and Fanny’s yer Aunt (meaning – you’re home free!)  When winding toroids, I often find that the first 1 or 2 turns aren’t quite as tight as the rest so when I’ve finished winding, I will unwind one turn from the beginning of the coil, then wind an extra one at the end, to keep the total number of turns the same.  Sometimes I will repeat that exercise a few more times until all the turns are nice and tight.  For this reason, I use enough wire to leave several extra inches at each end.

The next picture shows an anti-hiss filter that wasn’t in the earlier pictures, which I tried and ended up removing due to a low-frequency oscillation it was causing at the higher volume settings.   It was a series 0.01uF capacitor and 4.7K resistor connected from pin 1 of the LM386 to pin 5.   From what I have read, too low a value of resistor or too high a value of capacitor can cause the oscillation. I have seen other anti-hiss filters that used a 0.01uF cap and a 10K resistor, so it is very possible those values would have cured my problem. However, I was near the end of the project and itching to move on, so I just removed it. You can also see the 0.1uF capacitors on the inputs of the IC that have been swapped over to stop the uncontrolled oscillation, and are now crossing each other.  You may not have to cross these caps if you plan your layout accordingly -

Other than the problem with the loud screeching that was solved by swapping over the inputs to the LM386 (my schematic reflects the way the inputs were finally connected), the only other problem I had was with what appeared to be a defect in the 0.001uF (1,000pF) capacitor that leads from the tap on the coil to the emitter of the regen transistor.  I wasn’t getting any regeneration at all but on replacing this capacitor, the circuit broke into a nice loud hiss when advancing the regen pot.

I do have one ongoing issue that I hope someone can shine a light on for me, and that is a loud crackling sound when adjusting the tuning capacitor. At first, I thought a dirty rotor connection was the problem, but it only happens when extra padding capacitance is switched in by the band-switch   With no extra capacitance switched in, the tuning is smooth, but on the lower frequency bands, the receiver crackles when being tuned.  I need to try bypassing the band-switch and soldering the padding capacitors into circuit in case the switch is the problem. I’ll report back when I’ve done further work on this.

Incidentally, the main tuning range on mine covers approximately 7250 – 13000KHz.  Switching in a 47pF capacitor changes the range to 5825 – 8050KHz. I’m a bit limited with my receiver and test equipment here, so haven’t yet been able to determine the coverage of the lowest frequency band.

When first listening to the DR2, I had no idea what frequency I was listening to – only that I was probably somewhere between 5 and 12 MHz. I had no antenna connected (and at this point, hadn’t even built the RF amp stage) but started hearing CW. Lo and behold, it was Hank W6SX 180 miles away from me in Mammoth Lakes, CA. His CW signal was coming through well and in fact, this was the only time I have received CW in a satisfactory fashion on the Desert Ratt. There was no antenna – he was being picked up directly by the toroid.  Any concerns I might have had about the sensitivity of this receiver would have been immediately allayed.

I know the main question that is probably on your mind is – how does it sound, and what is it like to use? How does it “handle”? There are some videos of my Desert Ratt 2 in action at the end of this post. Apologies for the poor video quality, but my only video camera is 10 years old (and has a faulty CCD sensor). You’ve probably read articles about regens that describe the many and subtle adjustments that need to be made when tuning a regen in order to coax maximum performance from it. If you haven’t operated a regen before or if it’s been a while, it does take some time to get the hang of getting the best out of it. As you get further away from the setting of the regen pot where it breaks out into oscillation you lose selectivity and gain, so you need to try and keep the control set just under the point of oscillation. Loud stations can overload the detector, resulting in audio distortion, so it’s worth keeping an eye on the RF attenuation pot too. Also, if the attenuation pot is set too high (too little attenuation), you may get breakthrough from stations on other frequencies. There’s quite a bit going on to keep under control, but if you manage to keep all controls adjusted well, you can coax some pretty decent performance out of the set. I think this is why regens appeal to some people – we are incurable knob-twiddlers!

Stability is easily good enough for AM reception and with a logging scale fitted to the front panel, I don’t think it would be hard to find specific frequencies, as the majority of SW BC stations stick to 5KHz channels. In my casual listening so far, I have heard The Voice Of (North) Korea on 9435 and 11710KHz, Radio Habana, Cuba on the 49M band, Radio Australia on the 31M band, coastal station KLB (South Korea) on 8636KHz, the BBC World Service (forget which band or frequency), China Radio International on 9790KHz, WTWW on 5830KHz, and a number of other evangelical Christian stations (sorry, I tune them out and don’t pay them much attention.)

To sum up, you can definitely have a lot of fun and engagement with the bands on this set.  Being a regen, it is not the easiest receiver to operate, but you shouldn’t let that put you off. The best analogy I can think of is to reference the way that although an older British sports car may not have the finesse and performance of a newer sports model, it’s a lot of fun, and it’s lack of suspension gives you an exhilarating feel for the road that the more expensive cars cannot.

The Desert Ratt 2. A logging scale fixed to the front panel would make frequencies in the SWBC bands easy to find. I must do this sometime

My Ongoing Pre-Occupation With High Quality Air-Spaced Variable Capacitors

I’ve blogged before about air-spaced variable capacitors.  I’ve always liked ‘em, but I think my understanding of what makes a good one is maturing a little more. I was the winning bidder on a really nice-looking specimen on eBay a few days ago.  Ever since placing the winning bid, I had been excitedly looking at the pictures of it posted by the seller. It looked great. How exciting when it arrived in the mail yesterday and I got a chance to see it “in person”, as it were!  I got it for $11.50 and I think I scored -

It is NOS (New Old Stock) meaning that while it is old, it has never been used. Surprisingly, there seems to be quite a few of these high-quality NOS caps still floating around. Here are the specs for this series of variable capacitors from Hammarlund -

The cap that I scored has nickel-plated brass vanes. Brass is good, as it expands and contracts with changes  in temperature less than aluminum does (the other main material from which variable capacitor rotors and stators are made.) Also good are the bearings on each end of the rotor shaft. I can’t see them, but I assume the bearings are hidden away. It gets better. This capacitor has wide-spaced plates, meaning less change in capacitance with temperature changes than a part with closer spacing. Oh – and this is all firmly mounted on a ceramic base. Ceramic is a great insulator and I’m thinking that this must also be good for the physical stability of the component with regards to changes in temperature.

I just noticed something. As you rotate the shaft clockwise, the capacitance increases. It’s normally the other way around.  An end-stop prevents the shaft from rotating more than 180°, or this wouldn’t be an issue.  This must have been intended for use with a drive mechanism that translated the rotation of the tuning knob into rotation of the capacitor shaft in the other direction. I hope that the length of shaft protruding from the other end is enough for me to connect to, otherwise it might end up on the shelf for a few more decades!

One thing you may not appreciate from these photos is the feeling of solidity. This is a beautifully engineered part. See how the shaft is off-center? This makes for a non-linear relationship between the rotation of the shaft and the change in capacitance.  The change in capacitance occurs in such a way as to make the higher frequencies a little less cramped together, which is what happens with a capacitor where the relationship is strictly linear.

I mean, really – do variable capacitors get much better than this?  I don’t have definite plans yet for this little beauty but if my current interest in regens continues, I can see it paired up with the Jackson Brothers Dual Ratio Ball Drive and Dial I just ordered from the UK and used as the main tuning cap in a general coverage regen receiver – all built on a generously-sized aluminum chassis with front panel. (EDIT – unless I am able to connect the ball drive to the rear end of the shaft, this is not going to happen. Fingers crossed.)

Scroll back up to the top of the page and look at this fabulously engineered piece of American history sitting on top of it’s original box. That’s what it feels like to me – a piece of American history, and I got it for a few bucks. I will feel terribly privileged to be able to incorporate it into my own project at some point, though I’m going to hang onto that box.

Incidentally, while riding around Oakland, I noticed that this commercial space is up for lease.  It would be a good place for a ham-oriented business don’t you think?

Good Ops, Ben’s Best Bent Wire, and Some New Home-Made QSL Cards

Nearly every evening on 40M, I hear Bill Crane W9ZN for an hour or two coming in from Chicago. He’s a good op. I’m not sure what his top speed is, but I often hear him conversing easily with others at around 25wpm.  He always matches the speed of whoever he is talking to, which I think is one mark of a good op. I remember the first time I QSO’ed with KA7PUN a couple of years ago.  We were conversing easily at what was my comfortable speed back then (which was probably around 16-17 wpm).  I thought that was his regular comfortable speed until I heard him in QSO a few days later with another station sending much faster. I realized that he had matched my speed and felt very grateful to him for making me feel comfortable in that QSO.

Anyway, back to Bill. I first noticed him on the band for a style of sending that incorporates a variation on the “Ben’s Best Bent Wire” routine that commercial operators used to use in order to loosen up their wrists before a shift. At the time, I wasn’t familiar with this type of routine and only knew that Bill had a style that made him stand out on the band for me.  Here’s what I’m talking about.  This is Bill as recorded last night -

I imagine that a few decades ago, this kind of routine was more prevalent on the bands, but W9ZN is the only station I have heard doing it.  Some people would probably prefer to perform their warm-up routines off the air, but it sure is a good way for Bill to be instantly identifiable. A little online research seems to indicate that he was a Chicago radio personality in the 60′s and 70′s, going by the name of Bill “Butterball” Crane. I’d sure like to QSO with him, but he never hears my puny 5W sigs.  He’s running QRO, and a regular presence in the segment from 7031 – 7034 most evenings.

I’ve also been busying myself with making some new QSL cards, firstly for QSO’s I make with the CC1 beta.  I was inspired by NT7S’ CC1 beta card, and wanted one for myself. I’m lucky to have Photoshop (CS2) and to have finally figured out the importance of layers and how to use them.  The initial version of the CC1 beta card that I came up with looked good on the screen, but due to the fact that I didn’t have a profile for the printer at my local Fedex Kinko’s (they probably don’t have one), the card printed out a lot darker than it looked on my monitor, and some of the text ended up being buried in the background.  I did eventually come up with 2 versions, both of which look OK when printed. One, in my opinion, looks better in print than the other, but I’m waiting to hear back from NT7S as to whether he agrees before I print up a few of one of these two.  These are not scans of the printed cards, but jpeg renditions of the original Photoshop files. Bear in mind when you’re looking at these, that the printer in my local Fedex kinko’s prints files darker than they look on-screen, so if you’re thinking these images look a bit light, that is why -

I finally seem to be getting the hang of using Photoshop to do these kinds of layouts so, bolstered by the success of these cards, decided to make another one. It took me a while to scan the G-QRP Club logo and change it from black on a white background to white on a transparent background, but now I know how to do it, it’s a piece of cake -

Of all these cards, my favorite is my basic 2 color one.  The following image, unlike the previous ones, is not a jpeg generated from the original Photoshop file, but a scan of the final printed card.  I did this because the color of the card stock does a lot to make the card look good.  It’s called “Sawgrass” and unfortunately, my local Fedex Kinkos won’t be restocking it once their current stock is gone -

It’s simple, effective, and prints out well on a variety of printers – no complex graphics that need to be rendered in accurate tones. On top of that, if I need to make a lot and am feeling a bit skint, it doesn’t look too bad in monochrome either.

The First CC1 to CC1 QSO – and a QSL as a Memento

I made my first ever QSO with the CC1 beta a week or so ago. It was with Jason NT7S (the designer of the CC1 and proprietor of Etherkit) and on top of that, it was the first ever CC1 to CC1 QSO. Very exciting!  I was hoping to have been the first ever QSO Jason had with his CC1. That honor actually went to WA0JLY, but I did get to be Jason’s 2nd QSO.

He was recording video of the QSO, which is up on his website if you want to take a look, though I am rather embarassed by my sending.  For some reason, I hadn’t plugged the paddle into the jack on the CC1 properly, and when I came back to Jason, the paddle went nuts and wasn’t sending what I wanted it to at all. I finally discovered the error, plugged it firmly into the jack and continued with the QSO. Jason for his part, (due also to nervousness at our historic QSO I’m guessing, just like me,) wished me 71 at the end of our brief exchange.  I like that! As I pointed out to him, 71 is like 72, but even better.  From now on, whenever I QSO with NT7S, I am going to sign off by wishing him 71. Perhaps that could become the default sign-off for any CC1 to CC1 QSO’s in the future? He also told me that my mess-up in sending due to not plugging the paddle in properly is one of those things that help create a narrative to remember these occasions with. Well, I guess so

I don’t normally collect QSL cards, but some are special. This one from Jason is one of those in my collection that have great meaning.  In the early days of radio a QSL, instead of being seen as merely the final courtesy of a QSO, was the much-desired proof that a hard-worked for contact had taken place.  The early hobbyist would labor hard building his entire station, and spending many hours adjusting and tweaking in order to make contacts with other amateur stations. QSL’s were highly-prized pieces of proof that validated the work of the experimenter. I got some of that feeling on receiving this card from Jason -

This, in my opinion, is a QSL in the best time-honored tradition of amateur radio.  I’m running off to Fedex Kinko’s this morning to do a test-print of the custom QSL I’ve designed for my CC1 beta and hope to be spotting myself on QRPSpots later this week once I repair the final that I fried. I’m still not completely sure what I did, but it most likely had something to do with a stray clipped component lead or metal screwdriver

The Etherkit CC1 1st Beta – A Trail-Friendly QRP CW Transceiver

About a year and a half ago, I posted that I had completed the first beta version of the Etherkit CC-Series QRP CW Transceiver.  It was a neat little rig, with low RX power consumption (of the order of 50mA – a bit less, I think), full DDS VFO coverage of any one HF band, a built-in keyer with memories, RIT and XIT, as well as firmware that could be updated at will with a simple AVR ISP programmer (you can get them for around $20). It also used a lot of SMT devices, and was my first serious project using these tiny parts (the KD1JV Digital Dial was the first).

My CC-20 beta worked, and I made quite a few QSO’s with it, including some DX. It wasn’t perfect though. The DDS VFO had some in-band spurs, the TX/RX switching produced a thumping sound, the input and output of the crystal filter weren’t as isolated as they should have been, you could hear some low-level processor noise on the receiver audio,  and the sidetone sounded a little rough too.  Although that sounds like a long list of woes, I think that anyone who designs circuits is used to tackling these kinds of issues one by one, until the dragon is slain. We (by which I mean Jason NT7S, the man behind Etherkit) did manage to improve the isolation of the crystal filter by a fairly good amount during this beta build.

Then he came out with the OpenBeacon kit and the EtherProg.  I knew he hadn’t forgotten about the CC-series, but I’m thinking he wanted to get a few other kits up and running before coming back to tackle it again, which he duly did.

The rig has been renamed the CC1 and although it retains the same basic architecture, there are a number of changes and upgrades to the design. It is still a monoband QRP CW HF transceiver (available in your choice of band) with an output of 2 – 3W (depending on the power supply), and it still has a DDS VFO (tuned with a real knob!) that covers the entire band, as well as RIT and XIT (useful for working split), freq readout in morse code and a built-in keyer with memories. The firmware is still also upgradeable via an AVR ISP programmer.  Although at this stage in the development it has not yet been implemented in the firmware, Jason thinks it should be possible to include APRS functionality and WSPR too. That’s quite a lot for a rig that is not much bigger than a pack of playing cards.

The beta kit arrived in a Priority Mail flat-rate box (what a neat sight on top of my mailbox!)  The enclosure is to the left, in the middle was the bag of parts for the EtherProg (a separate Etherkit product which can be used to update the CC1 firmware). The big bag on the right is the bag of parts for the CC1 -

The CC1 parts bag opened up to reveal the inner packaging.  The bag containing the bigger parts has been opened and those parts dumped into a mint tin.  The EtherProg, as I mentioned, is a separate Etherkit product and is available now, but I’ve included it in this photo. You can see the board slid partially into the enclosure -

A view of the underside of the board. Our beta kits had the microcontroller pre-installed. Currently, this was the only way Jason could supply it to us flashed with the firmware, but regular production kits will not have this IC pre-installed (it will have the firmware already flashed though) -

In true Etherkit spirit (the phrase “Open Source Amateur Radio” is on their home page), the beta testing forums are open for anyone to view here, and the forum for the CC1 beta is here. Only beta testers can post in these forums, but anyone can post in the product support forums which are here (you have to register first.)  The CC1 beta forums include schematics and an assembly guide which, although not final of course, will be of interest to anyone who might have an interest in the kit when it becomes available.

A couple of days of soldering, and the receiver section (which is about 85% of the circuit) was finished. Alignment consists of peaking 2 trimmer caps in the bandpass filter, and adjusting the BFO so that the wanted signal is in the center of the passband.  The passband for my filter is not flat – there is a definite peak in the response,  so I adjusted the BFO to place the wanted signal at the peak of the filter curve.  I already had a noise source that I had built to adjust the filters for my K2, and Spectrogram on my computer (for the same purpose) so I used these to adjust the BFO frequency.  Both the noise source and the use of Spectrogram are detailed here. With the receiver aligned, I have now spent every evening since just listening to it. I keep looking at it and thinking, “That little thing is a radio?”

Here’s the CC1 board with the receiver section completed -

You can see the GPS connector at the left-hand side of the board (the rear) immediately under the green key jack -

The onboard connectors are really great. They save a whole lot of hassle with wiring, and make it a lot easier to run the rig on the bench before putting it in an enclosure. In the following picture of the underside of the board, you can see U4, the 50Mhz master oscillator and to the right of it, U5, the DDS VFO chip. On the right-hand side of the board in the center, is U1, the NE5532 AF amplifier (I just saw a cat hair lying on top of U1 – those things get everywhere).  You can also see the space for U2, the transmit buffer -

At first, I thought the receiver wasn’t functioning correctly, because on attaching an antenna, I heard only a very faint increase in background noise. I tweeted to Jason and informed him as such, as well as posting to the other beta testers in the forum.  My theory was that the AF amp had low gain.  As it turned out, it was a combination of the bandpass filter being way off it’s peak, and the initial BFO freq placing the signal fairly well outside the passband of the crystal filter. Had I thought to peak the trimmers before jumping to conclusions, I would have realized that all was well.

The receiver was sounding good. The DDS spurs that were present in my CC-20 beta are no longer an issue.  The crystal filter has better isolation – there is still some room for improvement, and that will be improved further before it comes to market – in fact, Jason just suggested a circuit change in this direction that beta testers are implementing as we speak. The TX/RX switching is very smooth and the sidetone sounds nice. There is a sharp leading edge on the sidetone waveform which gives a clicking sound, but that will just require some simple shaping, which, once again will be taken care of in the production model. EDIT - another blog, and also a discussion in a Yahoo groupo, seem to have misread my last statement as meaning that there are key-clicks on the transmitted signal.  This is NOT the case. The transmitted signal sounds nice. I was referring to the sidetone only, which is a simple thing to take care of.  I emphasize also that this is a beta,  and we will most likely be taking this little rig through another beta before it goes into production. The other issue, the processor noise that was present in the audio, is vastly reduced and by the time you read this, will most likely be cured altogether, as Jason just re-wrote the firmware, which I am waiting to apply to my beta.  Things are looking very good for this little rig.

A couple more views of the board at this stage, before we move on -

Having confirmed that the receiver is working,  the final push was on to build the transmitter and complete the rig.  It didn’t take long – just the installation of 12 parts and 2 more toroids to wind.

Here’s the completed board, before installation in the enclosure -

The world of SMT seemed like a closeted world of intrigue and mystery before I built my first project using them.  I had read web sites detailing the use of solder paste and hair dryers, or toaster ovens for soldering these tiny little parts.  It was a while before I realized that you can actually solder them the good old-fashioned way – with a soldering iron and a roll of solder.  I pick up resistors and caps and place them close to their final resting place on the board with a fine pair of needle-nosed pliers. Then, with a small jeweler’s screwdriver, I gently nudge them into their exact position on the pads. While carefully holding the part down with the tip of the screwdriver, I tack-solder one end in place. Then I solder the other end, and go back to the first end to properly solder it.  I use a 1/32″ chisel tip and 63/37 .02″ solder with a mildly active rosin core.  0.015″ solder would be even better, as it’s easy to apply too much solder (which is where a good-quality de-soldering braid, such as Soder-Wick, proves invaluable.)

IC’s with fine lead pitch are a little trickier. The NE5532 AF amp was relatively easy, as the leads are far enough apart to solder them individually. Needless to say, a very clean and well-tinned tip is vital. I wipe my tip on a dry rag and tin it before every joint – unless I’m soldering a number of joints in quick succession one after the other, such as with IC’s.  The AD9834 DDS chip has leads that are too closely-spaced to solder them individually. The technique that I learned from Jason involves soldering all the leads on one side with a big wodge of solder, paying no attention to whether the leads are bridged together with solder.  Afterwards, you clean up the solder bridges with de-soldering braid and a larger iron tip. A larger tip is useful here because you can wick up the excess solder more swiftly in order to avoid destroying the chip. Jason posted a good description of how to do this in the assembly guide.  Search for U5 on that page and you’ll find the description, along with a picture.  Flux is said to be very helpful here.  I managed it with no extra flux (other than that in the solder) , but plan on getting some for future use.

The CC1 is billed as a trail-friendly rig, and the kit will come complete with a pre-drilled enclosure with silk-screened front and back panels.  The enclosure we received with our beta kits is the exact same enclosure that will go out with the kits, with the exception that ours weren’t drilled or printed.  So the following pictures represent roughly what the final CC1 will look like, without the silk-screened panels. There might be a slight adjustment in the spacing of the controls before the final production model too.

Firstly, this one’s for size comparison with my CC-20 beta -

The board slides into rails in the side of the extruded aluminum case and is held in place by the nut on the BNC connector at the back.  Here’s a couple of front views without the front panel -

Man, is this thing a beaut or what?

I’m very fond of this little rig. I’ve only made 1 QSO with it so far (with Jason NT7S) but have spent every evening listening to it. It’s great to have the earbuds in, listening to 40M on this diminutive little transceiver while working.

I’m hoping to get some audio up at some point, but it may take a while. If you’re wondering when you can get one of these, well, it’s still in development but at this point I think it’s safe to say that it will be coming out. I do know that Jason NT7S is a perfectionist and won’t release it until he feels it’s truly worthy, and all issues have been thoroughly worked out. The design is already very close to where it should be and there’s a great momentum behind it, but we still have a 2nd beta to go through  Stay tuned and we’ll keep you posted.

 

W9RNK’s WBR Regen Odyssey

About a week and a half ago, I received an e-mail from Rich W9RNK.  After a long period of home-brew inactivity (about 20 years) he decided to pick up the soldering iron and start building again. He said that my post on building N1BYT’s WBR Regen Receiver (the most popular post on this blog by far) had inspired him and I consider that a great compliment. If one of my posts inspires someone to do something they haven’t done before, or haven’t done in a long time then in my mind, it completely justifies having and keeping this blog.

He did get his WBR receiver working after some initial setbacks   It seems that his problems were caused by using a core material for the inductor that wasn’t suited for the frequency. He used a toroid with a blue core, which is quoted as not being suitable for frequencies over 3MHz.  On substituting the recommended yellow color-coded toroid, the receiver started working.  In his write-up, which I link to below, he shows the schematic of 7N3WVM’s version of the tank circuit which includes a 0.22uH inductor from the center-tap to ground.  The QRP-Tech Yahoo Group run by Chuck Adams K7QO made the WBR the subject of an informal group-build not too long ago and I noticed that some of the members experienced problems with sensitivity. Steve AA7U found that adding a choke from the center-tap to ground alleviated the sensitivity problem. Based on his experiments, he determined that the optimum value is around 1uH.  I had no problems with sensitivity, so my recommendation would be to build the WBR as per the original QST article, and to experiment with adding an inductor if you do experience low sensitivity. However, I do wonder why others have had these problems when I haven’t?  In the original article, Dan mentions that the length of the stiff wire connecting the center-tap of the coil to ground should be about 1″.  I was careful to make mine about 1″, as well as to connect it to the ground-plane of the PCB, as opposed to connecting it to some other grounded point on one of the potentiometers or the enclosure. That’s all I can think of but hey – if an inductor works for you, that’s great.

The other main issue Rich had with his WBR was drift.  I hadn’t measured the drift on mine as it seemed to be quite good. However, prompted by his observations, I decided to take measurements on mine today.  From a cold start, it showed by far the biggest drift rate in the first minute (no surprise there) by drifting 120Hz downwards. In the next 14 minutes, it drifted another 190Hz down, for a total drift of 310Hz in the first 15 minutes. In the next hour, it drifted another 240Hz down, and the hour after that, 100Hz.  I would have been interested to see what the drift was in the 3rd hour but boredom, and the lure of other tasks to complete prompted me to stop!  My WBR (which has an AF preamp stage, unlike N1BYT’s original design) still only draws 13mA so when using it, I used to leave it on all day.  I’d find that I could set it on a net frequency, come back an hour or two later and hear little drift, so I’m thinking that had I measured the drift in the 3rd and 4th hours it would have been less still. Not world-class, but not bad at all for a circuit with no attempts made at temperature compensation, and intended just for general listening.

Here is W9RNK’s write-up detailing his odyssey towards a working WBR Regen.  It’s a pdf file, so make sure you have a pdf reader on your computer.

Rich W9RNK – WBR Build

Many thanks to W9RNK for writing this up, so that it can be shared with others. Hopefully it will serve as an inspiration to anyone else who hasn’t picked up a soldering iron in a while.

PS – I do, like Rich, think an AF pre-amp is a worthy addition. I took N1BYT’s advice and used the same pre-amp that he used in his OCR II Receiver (Sep 2000 QST). Here’s the schematic of the AF stages of my version of the WBR -

That’s it for now.

TX5K – A Well-Run Operation and an Interesting Island

Today is the last full day of the TX5K team’s operations from Clipperton Island and they have already dismantled site B.  Site B was mostly CW which meant I had to abandon my hopes of getting them on 40 and 30 in order to achieve a clean sweep on QRP CW for all bands 80 – 10M.  However, getting a single DXpedition on 6 bands is a first for me, and I’m pretty happy with it.

Clipperton Island is an interesting place. In modern times, 4 nations have fought for ownership, partially for it’s strategic positioning, and partially for it’s surface layer of guano (translation – the island is covered in bird-droppings.)

The last attempt to permanently colonize Clipperton ended in tragedy in 1917. I’ll leave you to read about it but as Joel KB6QVI said to me, a film could be made from the drama that occurred on this small island in the North Pacific. Indeed it could, and not much in the way of dramatic license would need to be taken in order to make the story compelling for a modern movie-going audience. The Wikipedia entry about Clipperton Island is here (opens in a new window), but you’ll find a more lively read in this article.

Two things struck me almost immediately about TX5K -

1) It was a well-run DX-pedition. Good operators with good ears.  I’m referring to the CW side of the DXPedition as I almost never use SSB when DX’ing,

2) The ability to see the QSO you have just made on a map on their website, as well as see your QSO in their online log is fantastic.  No waiting for a log to be uploaded – the website updates every 60 seconds and with each of the 6 QSO’s I made, I saw myself in the log no more than 2 minutes after making contact. No more wondering whether to make an insurance QSO.  This kind of technology can only have a positive effect on the QSO rate, although I did hear the op on 40M last night firmly talking to a station that had already made 5 QSO’s with him. Obviously that station wasn’t familiar with the near real-time online log. The software was written by expedition leader Robert Schmieder KK6EK, and sets a new standard for DX-peditions of this size,  IMO.

Here’s how I managed. Got ‘em on 6 bands with 5W of CW to a 66 foot inverted vee with the apex at 47 feet (partially obscured and partially in the clear).  As Justin VE3XTI commented, I sure suck at SSB

John AE5X got a clean sweep on CW from 160 – 10 which, knowing John’s experience, came as no surprise at all.  I pretty much expect that kind of excellence from him!

Aerial photos of the DX-pedition site can be seen here.  Teams who mount these events go to great lengths so that we can have our DX QSO’s, so no whining on the cluster because the entity you want is not currently taking QSO’s in your preferred mode from your part of the world. In fact, don’t treat the cluster as a message board, period.

Cordell Expeditions, who mounted the TX5K operation, are planning an expedition to Heard Island in Antarctica next year. Definitely one to look out for.

In the meantime, I’ve got my sights set on 9M4SLL, which takes place March 10th – March 18th. Thanks for the tip-off Jason

The ARRL 10-Meter Contest and Checking In To SSB Nets with QRPp

A few days ago, Bryan Herbert KE6ZGP, posted on Facebook that he’d come first place in his section for Single Op QRP phone in the 2011 ARRL 10-Meter contest and posted a picture of his certificate. I thought it was pretty neat-looking and gave him my congratulations, telling him that I was envious, but happy for him, and also noting that I’d never won anything like that, as 2 hour sprints were about the most I had any kind of stamina for.

Then a little over an hour later, the front doorbell rang.  It was the mailman with a few packages for my neighbors and a large brown envelope for me, containing this -

I had completely forgotten entering the ARRL 10-Meter contest.  It was almost a year ago!  I had participated (casually), submitted my log, and promptly forgotten about it.  Now I know that I am by no stretch of the imagination even a semi-serious contester, so figured that there probably hadn’t been many other QRP CW contenders in my AARL section.  On checking the ARRL site I found that there had been just one other. Nevertheless, I was very happy to have this piece of paper, which is already framed and hanging on the wall.

In other news, I have been doing no home-brew – sorry about that. My INTJ mind is either very pre-occupied with something, or not noticing it at all. Currently, I am engrossed with the task of committing as many music CD’s as possible to hard drive in order to de-clutter my living space. It’s all part of a long-term plan for the future which may include living in an RV, or simply another apartment.  Either way, I want less stuff, and 10,000 music CD’s are awful heavy when it comes to moving time. While busying myself with the task of ripping and scanning during the day, I have had the K2, my main station rig, tuned to 40M and in particular, the Noontime Net on 7268.5 KHz. My mind works in strange ways, and for the 3 years I was into CW, that was all I was interested in.  I had spent plenty of time operating SSB (and FM on the 2-meter band) in the past and it no longer held any interest for me – it really didn’t.  Every now and again, I would tune up to the phone portion of whatever band I happened to be in and after just a few minutes of listening, wonder how anyone could remain interested in amateur radio if SSB was their main mode of operation. I like the mental challenge of decoding a CW signal in my head, and that is as much of an attraction to me as the radio part.  Decoding SSB in my head was a skill I learned when very young, so there’s not much challenge there!

Nevertheless, while busying myself with the task of ripping CD’s and scanning all the artwork, I had the K2 tuned to 7268.5 KHz from about 9:30am – 2pm every day to listen to the Noontime Net.  I have never done a lot of listening to nets before and at first, couldn’t quite understand the attraction of checking in to a net on a regular basis when the main purpose of doing so seemed to be to just check in and then not do much else. However, there is a little bit more to it than that, and after a few weeks of listening, I started to get a feel for it and checking into the net became a welcome part of my daily routine. EDIT: After a few months of checking in daily to the Noontime Net, it has become a very welcome part of my daily routine and to amend what I said a few sentences earlier, there is a lot more going on with a net like this than first meets the ear. It is a very well-run net that manages to check in a lot of people every day, while still having time for the occasional bit of friendly chat. It never wanders into the territory of “clique-ness”. The balance between the business of checking in a lot of people, while retaining a sense of camaraderie and connectivity is perfect. KV7L Lynn is the net manager, and along with every single one of the net controllers, is to be commended for pulling off this feat. It’s not an easy thing to do.

The Noontime Net is a traffic net, and traffic is indeed passed on occasion.   After a few weeks of listening almost daily (at first on the WBR regen receiver when I was still fresh out of building that) I began to recognize the regular characters,  including the very distinctive voice of Clyde AA7WC who took early check-ins daily until his recent illness. I checked in a few times, and then having the radio on and listening to the net in the background as I did other things around the shack, checking in on an almost daily basis started to become a welcome part of my daily routine. Many days, I will check in fairly early, and the re-check later.  It’s also interesting to listen to many of the same stations regularly to see how propagation affects how we all hear each other – and this brings me to the aspect of the net that has interested me the most in the last week or two.

I had been checking in to the Noontime Net with my K2′s full output power of 15W.  About 10 days ago, I decided to dial down the power to see whether I could still check in with one of the net control stations.  On CW, you can turn the power down to 100mW, and on SSB, 1W.  I dialed down to minimum SSB power and called Lynn KV7L in Princeton, Oregon. I thought I was running 100mW but forgot that on SSB, even though the K2 may indicate an output power of 0.1W, it is actually putting out 1W. To my surprise, Lynn gave me a 58 report. He is 412 miles from me. I also got a 59 report from a station in Bakersfield, about 245 miles to the south.  Thinking I was running 100mW, I was ecstatic but in retrospect,  a 58 report from a station 412 miles distant when you’re running 1W of SSB is still pretty good.  Since then, I have regularly checked into the net with just 1W and am heard well by KV7L in Princeton, OR, W6FHZ in Reno, Nevada and N7WH in Boise,  Idaho.

I often received unprompted reports of good audio too, for which much of the credit has to go the K2.

All of this has gotten me quite excited about seeing how low I can take the power and still successfully check in to the Noontime Net. I cannot dial the power on my K2 below 1W on SSB,  so the next step is an attenuator.  Even though I have not been doing any home-brew and am concentrating most of my efforts on non-ham radio pursuits, I think an attenuator is in my immediate future.  I would love to be able to tell net control that I am running just 50mW – or even 10mW! Stay tuned to this space.  Maybe I can get something together in the next few weeks. (EDIT – I ordered an attenuator online before this post was even finished – keep reading.)

The upshot of all of this is that although when people think of QRP, they usually think of CW, and the 13dB disadvantage of SSB compared to CW is well-known, you can still achieve things with QRP SSB. Bryan Herbert KE6ZGP has made many great DX contacts with just 5W of SSB (and even FM during 10M openings) and he told me recently how he thinks the potential of QRP SSB is underestimated.

On another tack, I was in Cost Plus the other day and saw a mint tin that was just crying out to have something built in it.  Some people think of electronic gadgets as boxes of “black magic” and indeed, even us hams think of radio as quite magical.  I like to put as many of my mint tin projects in different looking tins as possible, to make them easier to tell apart from each other. I think this tin fits the bill perfectly. What piece of black magic could I build into this enclosure?

My recent experiences successfully checking into the Noontime Net with just 1W PEP of SSB made me keen to see if I could check in with even less power.  The minimum amount you can dial the power down to on the K2 on SSB is 1W, so to get it down further I would need an attenuator.   I was looking for a cheap way to do this without having to build anything, and settled on this 20dB inline attenuator that I got from eBay for $6.99 including shipping -

I like it because unlike the step attenuators in regular enclosures, I don’t have to come up with an extra BNC to BNC cable.  It’s quick n’ dirty n’ cheap. Without setting up a separate receive antenna, the attenuator also attenuates the signal on receive, but as I plan on initially using it to check in with net control stations that are very strong here, that won’t matter.

In theory, when I set the K2 to 1W and connect the output of it to the attenuator, which is terminated in a 50 ohm load, the 1 watt should be attenuated by 20dB, giving me a final output signal of 10mW into 50 ohm, but when I connected the output of the K2 (set at 1W in CW mode) to my OHR WM-2 QRP Wattmeter, the output of which was terminated  in a 50 ohm load, I measured 40mW and not 10mW.  I do believe the meter to be calibrated accurately  so I am not sure what is going on here.

The next step should be to construct my own attenuation pad to verify these results but for the meantime, the Noontime Net was in progress and I wanted to see if net control could hear me. KD7RTE was taking check-ins and couldn’t hear me, but Lynn KV7L in Princeton, OR gave me an S3. He is 412 miles distant – not bad for 40mW of SSB.

I have gotten into the habit of checking into this net with 1W PEP and I think I will continue to do so, but the quick n’ dirty experiment with QRPp was pleasantly fruitful. I kind of wish it was possible to use the front panel control on the K2 to dial the power all the way down to 100mW on SSB, the way you can on CW – or even lower. QRPp is fun! 40mW is flea power, and it’s especially gratifying for a signal of such low power to be copied 412 miles away on SSB.

In other news, it has become harder to operate the radio, because Sprat The QRP Cat has decided that she likes biting the fingerpieces of my Bencher paddle.  I try to put the K2 in test mode so she doesn’t transmit. When she’s not practicing the code, she just likes to get in the way when I’m trying to operate the radio, and steal the spotlight -

S9 +10 QRM Problem Solved and a Cat Adoption From HRO

Shortly after making the last blog-post, my radio operating activities were severely curtailed by QRM that registered well over S9 across all the HF bands. It wasn’t continuous but would come and go seemingly at will throughout the day and night – there was never a time when I could be sure it wasn’t going to obliterate whatever I was listening to.  Several times it would appear while I was in the middle of a QSO, and cause me to QRT prematurely. I hoped that the QRM would disappear as mysteriously as it arrived, but after a few weeks, this “hoping” approach didn’t seem to offer as much, well, hope as it had before.

I live in a 100 year-old house that was converted several decades ago to individual studio apartments.  The first step was to verify that the QRM was coming from my building, so I walked around, both inside and outside, with a small battery-operated portable Grundig shortwave receiver. Inside the house, the QRM had a fairly even signal strength, becoming a little stronger as I got closer to the walls. When walking outside the house, the QRM faded rapidly, only becoming stronger as the radio got closer to the outside walls of the house.  I concluded that the QRM was being carried on the AC wiring of my apartment building and was being generated by something plugged into the AC.

I know all of my neighbors, and relationships with all of them are cordial, except for one. She decided a while back that she just didn’t like me, and I tired of trying to make peace. It seems that wherever I go, there’s always one, but that’s a different story  Even though I get along with nearly all of my neighbors, I wasn’t sure how successful I’d be approaching each one individually and requesting permission to go on an RF snooping exercise inside their apartments. It wasn’t really something I fancied doing.

So what to do? I had no idea, and for the next week or so, had partially resigned myself to the idea that I was just going to have to deal with the fact that I was now living in an environment that made my ham radio and shortwave listening activities much, much more challenging. How very frustrating!  Many times in the last few weeks, I had asked myself if anything in my apartment had changed recently and every time  the answer I came up with was that it hadn’t. Then I remembered something.  Recently, I started fostering a sweet and very shy 10 year-old cat called Chala.  You can see her at the end of this last blog-post.  The foster agency with whom I was working gave me an electric pet heating pad for her – and that was at about the same time the QRM began!  It was like a light-bulb going on in my head and of course, it was too good to be true.  But it wasn’t – I unplugged the heating pad and the QRM disappeared instantly.

The level of QRM was so high and so well distributed throughout the whole house, it was hard to believe that a little 9″ square heating pad could cause so much interference, but it sure did.  Luckily,  I don’t think she really needs it anyway. It’s just as well, because it’s not going to be used at this QTH any more.  Any locals want a pet heating pad for free?

Be warned – this pet heating pad will radiate S9+ QRM from the wiring in your house/apartment on all HF bands!

I have been doing very little radio recently other than checking into the occasional SSB net while doing other things, so there is no news of any new home-brew projects I’m afraid   There is nothing planned either, so I may be posintg even less frequently in the future than I have been doing in the past.  My interests are shifting back towards trying to get as much of my music collection as possible transferred onto hard drive in case I purchase an RV and take to the road in a few years. The other thing that has been on my mind is cats.  I’ve begun the steady inexorable march towards becoming a certifiably crazy old cat guy. My new companion, Chala, is a sweet kitty, but she’s very shy. My last cat, Rug, was a lot more outgoing and I miss that. Chala’s great and I derive a lot of of satisfaction from giving her a safe, comfortable home after her ordeal on the streets, but I have been wanting a little more kitty interactivity.

It was with this general mindset that I made a trip to the Oakland Ham Radio Outlet about a month ago in order to buy an 8-pin mic connector. It was also an excuse to browse the magazines and books. While standing at the counter, the employee who was helping me walked out from the back room and was being followed by a little kitten, who was happily prancing around and generally being very friendly to anyone in the vicinity. HRO wasn’t a place I’d normally expect to see a cat, so I was curious to know why she was there.  It turned out that Nick, one of the employees, had discovered her trying to keep warm that morning by pressing herself up against the engine of his truck in the parking lot. He pulled her out, and she spent the rest of the day in the store happily attaching herself to the employees. When she jumped up on the counter, stood on her back legs, put her two front paws on my shoulders and gazed at me, I was hooked. Then when she curled up on the counter in front of me, pressed her little body up against me and started purring, I was a goner.  I asked Mark WI7YN, the manager, what he was going to do with her. He said that he didn’t want a store cat, so had been thinking of asking the customers if they wanted a kitty. Without giving it a second thought I said that I’d take her, bundled her into my backpack and cycled home with her.  So began a love affair with this fabulous little kitty companion -

What to call her?  I wanted a name that reflected where she was found, but anything too ham radio oriented wouldn’t make sense to my non-ham friends (who are most of the people I know.) In the same way that hams have both a regular “civilian” name and a call-sign, this little kitty has her regular name, which is Sprout – as she’s a cute little Sprout!  Her ham radio name is “Sprat The QRP Cat”. I hope the GQRP Club approves -

Sprat The QRP Cat

I still haven’t used the 8-pin mic connector I bought that day but I’m looking at it this way – I paid an $8 fee to adopt a kitty and had a free mic connector thrown in. Thank you Mark WI7YN and the team at Oakland HRO.

PS – Sprat The QRP Cat was not micro-chipped and not spayed.  The vet estimated her age at 5 months. She has since been micro-chipped, spayed and has had her shots. She’s in fine shape!

Building and Installing The Internal ATU, SSB Adapter and 160M Receive Options For the K2

F5VJD’s DSB80 is not completely finished.  I need to get rid of the chirp, and the first step will be to clear up some of my shaky grounding practices. I’d also like to build a sidetone oscillator. However, I spent a lot of time and put quite a bit of work into getting it into the case and wiring it up, and I really needed to take a breather before continuing with it.

In the meantime, Eric WA6HH posted a heads-up to the Elecraft reflector that there would be a slight price increase on several of their products in mid-September.  No more information than that was provided.  I knew that at some point I wanted to assemble several options for my K2 and, not knowing whether the options I wanted would be affected by the price increases, decided to go ahead and order them. As it turns out, mid-September came and went, and the options I ordered are still the same price but that’s OK – I wanted them anyway.

After working on the DSB80, assembling a few Elecraft K2 options would be a nice bit of relaxation. All I had to do was follow the instructions and everything would work – kind of like knitting a sweater according to a pattern. You do what they say and as long as you execute well, it works out perfectly.  That has been my experience with Elecraft so far, and these options were no exception.

The options I ordered were the K160RX 160M receive option, the KAT2 20W internal ATU, and the KSB2 SSB adapter. The 160M receive option was a bit of a no-brainer at just $40. I don’t do that well on 80 with my current antenna, so the chances of me doing OK on 160M are pretty slim, but one day I’ll be in the position to put up an antenna for 160M and on top of that, I was keen to see how far beyond the band edges I’d be able to receive – it was a way to increase the general coverage capabilities of the K2 just a little. Plus, the ability to have a different antenna for receive could be useful. The internal ATU would make operation simpler.  I’d been using an MFJ manual tuner, and wanted to be able to hop bands and frequencies more quickly (yes, lazy I know).

The SSB option wasn’t in my head when I first built the K2. I was so into CW, and loved the simplicity of a high-performance rig assembled solely with CW in mind.  However, very occasionally, I have heard stations on SSB that I wanted to contact. One station in particular was in the Philippines who was calling CQ with no-one coming back to him.  I don’t remember the band, but he was so loud that I knew he’d be able to hear even a QRP signal from me. It was one of those moments where I thought it’d be neat to speak into the mic and make an instant, easy contact with a DX station. Plus, even though I don’t use digital modes much at all, it would allow me to use WSPR occasionally if I so desired. I was also harboring a fantasy that I might want to start rag-chewing on phone one day but in retrospect, that was probably an unrealistic hope As it turned out, the novelty of having SSB was starting to wear off after 2 QSO’s, and was mostly gone after the 3rd.  It’s still a good extra capability to have though, and I do like going through the process of assembling, installing and aligning circuits.

The K160RX 160M receive option is  a simple little board that doesn’t take long to put together, so I decided to have a go at it first. The board is upside-down in the first shot.  Sorry about that. Hmmm – looks like a couple of my foster cat’s hairs made their way onto the relay on the right-hand side. Those long-haired cats leave their marks everywhere……..   (Scroll to the end of this post to see where those hairs came from.)

Installation of this option is straightforward. On receive it tunes down to about 1600KHz, though with reduced sensitivity.  I’m not yet sure what the upper limit is. The board adds a 160M lowpass filter for the separate RX antenna, and switches in extra capacitance in the bandpass filter on the main RF board for 160M.  I’ve only heard one station on Top Band so far, though I’m sure the next Stew Perry contest will change that. Here’s what it looks like installed in the K2:

Looking from the rear (the plastic “boot” over the antenna connector is to remind the user not to use that BNC when the internal ATU is installed – it is supplied with the internal ATU kit) -

Next up was the KAT2 Internal 20W ATU. This next picture of  the top-side of the partially completed LC board (the ATU is comprised of 2 boards) is posted here to illustrate a point.  I had a Twitter conversation recently with a ham who wants to build the K2, yet has a problem with his soldering generating a large amount of residual flux.  He couldn’t figure out why after soldering, his boards have so much flux on them.  I referred him to the Elecraft soldering guide and after reading it, he concluded that he was putting too much solder on his joints. This reminded me of Don W3FPR, who repairs and aligns a lot of K2′s, saying on the Elecraft reflector that he sees a lot of K2′s with way too much solder on them.  If you use a thin and mildly active solder along with a small tip on your soldering iron, you can easily regulate how much solder flows onto the joint, and ensure that you use the right amount and no more.  I use Kester RMA 285 in .02″ diameter (the RMA stands for “Rosin Mildly Active”.)  My tips are 1/32″ and 1/16″ diameter chisel tips – that’s 0.8mm and 1.6mm.   With boards that have plated-through holes, thin solder and a small tip will allow you to apply enough solder to fill up the hole and just a little more. From what I’ve read, ideally, you want to avoid a concave shape of solder in the hole – you should have a very small fillet of solder leading up to the lead, with the operative phrase being “very small”. I veer towards making the joint almost flat with the board – though flush cutters won’t allow me to make the joint totally flat. If you are applying the minimum amount of solder needed to make the joint, you wont have problems with solder bridging adjacent pads and causing unwanted shorts. You also won’t need to clean the flux off with a flux cleaner, because there won’t be much, and mildly active rosin isn’t corrosive enough to cause a problem if left on the board.  I think I did end up applying a little flux cleaner to this board eventually, but this picture was taken before applying it. What little flux there is, is honey-colored and hard to see in this picture, but I hope it illustrates the fact that unless you’re very particular about appearance, you don’t need to use flux cleaner if you’re using the right kind and amount of solder:

Another view of the top-side of the partially completed LC board:

Incidentally, if the board you’re soldering on doesn’t have plated-through holes, you will need to apply more on top of the joint in order to make a reliable connection. The capacitors on the above board are bent over per the instructions in order to achieve the necessary clearance. The underside of the LC board contains all the relays. If you look closely, you’ll see that relay K13 is not quite parallel with the other relays. These kinds of oversights on my part drive me potty but are of no consequence to the performance of the circuit:

I don’t have a picture of the whole of the top-side of the completed control board, but here’s a view from the side. It’s not a very good photo technically either but it’s all I have. Sorry about that. Note that the NPO cap behind the toroidal transformer is not the stock part (in case you were wondering why yours looks different.)  The stock part is a monolithic cap. I thought that I might have damaged mine (long story) so replaced it with this part. As it turned out, the stock part was fine, but as this NPO cap does a perfectly good job in it’s place, I left it in -

The finished KAT2 Internal 20W ATU:

At the bottom is the control board, and on top, the LC board, containing all the capacitors, inductors, and the relays that switch them all in and out of circuit when finding a match. The pink piece of foam underneath was simply to raise the ATU to the right angle to get a good shot.  I have become a bit lackadaisical recently, as I really should have looked for a way to support the board that wouldn’t be visible to the camera. I’m slipping.  Sometimes I just want to take the pictures and get to the next part of the project:

The completed unit showing the underside of the control board, with the 2 trim-pots that set the readings for forward and reflected power:

The KAT2 20W Internal ATU installed in the top cover of the K2. I’ve placed black electrical tape over the unused holes to prevent dust from getting into the K2.  My top cover was supposed to have been supplied with green tape over these holes, but it had already been removed when I received it.  Not a biggie:

Phew – only one more option to go – the KSB2 SSB adapter. I loved assembling the KSB2 board, as it is a little more densely packed than the K2 or any of the other options I had built so far. It’s fun building small things. Here’s the top of the completed board, showing all those lovely crystals (it’s a 7-pole crystal filter) -

The manual says to install the crystals flush with and tight against the board.  I usually try to build my circuits so they will be as reliable as possible and although there was an insulating solder mask on the top of the traces that connect to the crystal terminals, there was, in my estimation, the slightest chance that if the integrity of that solder mask were to be breached, there was a possibility of the pads being shorted out by the metal underside of the crystal casing.  It’s a long shot but why risk it if you can avoid it? I spoke with Richard at Elecraft who confirmed to me that if I were to space the crystals above the board by the thickness of a piece of paper, it wouldn’t adversely affect the performance of the filter. That was all I needed to hear, so that is what I did.

Although I have definite OCD tendencies, I do keep them in check on a regular basis.  Functionality is an important factor and although it’s nice to have all my toroids looking neat, I recognize that there is no difference in functionality between a toroid with perfectly spaced turns and the ones that look like mine in the picture below. Some of my toroids turn out looking really nice and some of them look just OK, but they all work just fine  -

The underside of the SSB adapter board. RFC1 and RFC2, though marked on the underside of the board, are actually installed on the top-side. They are wound on very small FT23-43 cores and the only reticence I had about top-mounting them was that it was hard to avoid the windings coming very close to the metal cases of the adjacent crystals. I know the windings are covered in insulation, but I’m not overly keen on it. Unavoidable though. You can see how close the mini toroidal chokes are to the metal crystal cases in the direct overhead shot of the board, 2 pictures above. Here’s one of the underside of the board -

There are several reasons I post many pictures of my projects. I know there are times when I’m assembling something and I want to know how other people do it.  Occasionally, if an instruction in a manual is unclear to me, or can be interpreted in different ways, I’ll go trolling the internet to see what other people who built the same thing ended up with. Perhaps I can help a few people by offering up my pictures. Also, it’s fun taking pictures!

Before adjusting the carrier balance, the instructions in the manual say to place the wiper of the carrier balance trim-pot at approximately mid-travel. I did this and found that very little further adjustment was necessary to null out the carrier. I have only performed a rough adjustment using the S-meter of the K2 so far, but I’m pretty close.

All these options required a small number of modifications to the main RF board on the K2. Some builders who are reticent about desoldering components from their beloved K2′s have opted to use the Rework Eliminators.  I did think about it but decided against using them for 2 main reasons. Firstly, I’m cheap frugal and was already stretching my finances a bit even by buying just the basic K2. Secondly, I’m quite good at soldering and desoldering and don’t find it a nuisance at all to have to partially disassemble a rig and desolder a few components in order to fit a new option.  I have actually enjoyed the partial disassembly of the K2, as I got a chance to renew my acquaintance with it’s innards. The K2 PCB’s are high quality boards. You’d have to apply an awful lot of heat for a long time in order to damage them.  I did turn the flux darker in color in one or two places, but a quick application of flux remover with a plumbers flux brush took care of that.  The places on the K2 board where I have removed jumpers and desoldered components still look really good.

As a continuation of the last topic,  I hope you’ll allow me to air a few more opinions about soldering and the K2.  I do understand how someone who hasn’t built a K2 before would want to protect their investment. The Rework Eliminators are very appealing in this regard. In my opinion, they could be useful if you are going to be changing options a lot. Even a good board in the hands of an experienced tech will start to look shabby if soldered and desoldered enough times. Now that I have installed the 160M receive, internal ATU and SSB options, I doubt very much that I will need to remove them. If you’re experienced at soldering, the lack of Rework Eliminators  in my opinion is not a problem. If you’re not experienced at soldering, in my opinion also, you shouldn’t be building a K2.

Please don’t interpret the last sentence as a discouragement from building one of these absolutely brilliant rigs. If you have any inkling to build a K2 – please do.  It might be the last chance you’ll get to build this kind of a kit at the component level.  It’s certainly a classic of our times.  If you’ve ever thought that you’d like to build a K2 – definitely do it, but make sure that you can solder well before you start.  $740 plus tax + shipping (at time of writing) is a lot of money to spend on something if you’re just going to drown it in solder!

If your response to this is is something along the lines of “But my soldering isn’t very good and it’s always been that way” then I challenge you to improve it. It can be done.

As part of installing the SSB option, some extra components have to be installed on the control board – some capacitors, a couple of transistors, and a set of header pins for configuring the mic wiring for whatever mic you will use. For configurations that require adjacent header pins to be connected together, you can use jumper blocks.  The mic I decided to use was an old Heil Traveler headset.  I didn’t like the bulk of the thicker wire and adapter cord (that in my case was configured for an FT-817) and the small plastic box that contained a PTT button and freq up/down buttons, so I chopped it all off and got to decide how I was going to wire it to the 8-pin mic plug.  I decided to go with the straightforward configuration that the Elecraft MH2 mic uses i.e. adjacent pins connected to each other.  If I decide in the future to use any different type of mic, I’ll probably use a home-made adapter cable so that I don’t have to go into the K2 and re-configure for each different mic -

Here’s the KSB2 SSB Adapter installed on the K2 main RF board.  There is a hole in the SSB adapter board that allows the frequency counter probe to be attached to TP2, but I’m a little concerned that although it can also still make electrical contact with TP1, if I want to seat it fully into TP1, it looks like I’m going to have to file some of the edge off the KSB2 board -

Those blank holes on the back of the K2 are starting to fill up.  The blank holes are supposed to be covered with green masking tape as supplied, but that tape had already been removed on the covers supplied to me, so I have covered the few remaining holes with black electrical tape. Looks OK and keeps the dust out -

I’ve had a few SSB QSO’s with the K2 so far and out of 5 QSO’s, 4 of the stations gave me unsolicited reports of excellent sounding audio. One station said that perhaps I could use a few more highs and a little less on the low end, but that I should be careful about messing with the audio too much as it already sounded very good.  I may adjust the carrier placement in the filter pass-band just a little to accentuate the highs, but I think I’m pretty close.

Assembling and installing these options has been an enjoyable exercise.  It has given me the opportunity to re-familiarize myself with the insides of the K2 and has only solidified my liking for this rig, as well as my respect for Elecraft. The ham community is very lucky to have this company making these great products for us.   My budget has taken a bit of a beating this month, but I’m hoping to be able to get the K60XV 60M option pretty soon

Oh – and those hairs on the relay in the very first picture in this post? They came from Chala – a 10 year-old kitty that I’m fostering right now. There is a group that goes out every night and feeds the feral population here in Oakland. Chala was amongst those cats, but one of the volunteers brought her into the shelter because she was not doing at all well on the streets. She’s a shy kitty with a very sweet nature, and was unable to defend herself from the other cats. She was in really bad shape when first brought into the shelter, but is slowly starting to settle down and get comfortable here. She’s a sweetheart and as you saw from the photo of the K160RX option, is already starting to leave her mark on my construction projects

Chala is pondering how the K2 will perform on 60M when I build the K60XV option.