Dave Richards AA7EE

January 24, 2015

National Radio Company Dials and Reduction Drives

Filed under: Amateur Radio,Ham Radio,QRP — AA7EE @ 9:19 am
Tags: ,

There are a few things I’ve been wanting to write about here. A couple of fellow builders have regen builds that I’m keen to relate. I have also wound two more coils for The Sproutie and would like to pass the details on, as well as a few thoughts on the subject, and coil-winding tips. However, I am experiencing a certain malaise toward writing at the moment, so will take the easy way out for the time being and simply post pictures of some vintage parts I recently acquired.

Like most builders, I like to keep a stash of parts that my be needed for upcoming projects. I don’t buy indiscriminately though – a part needs to have a good chance of being used for me to consider taking it on board. During my career as a DJ and voiceover guy, I collected CD’s fairly indiscriminately over the course of a couple of decades and ended up with a large collection that has taken a great deal of time and effort to slowly reduce in size. I don’t want to do the same thing with radio parts. However, given that I think I still have a regen or two left to build, there are a certain number of quality variable capacitors, reduction drives, and dials that still need to be given a good home in my shack :-)

I get many of my vintage parts from eBay. I am quite picky about condition, and also reasonably disciplined when it comes to price.  There’s a Hammarlund MC-100-M variable capacitor on eBay right now. It’s used, in good condition, and it has a “Buy It Now” price of $60. There is no way I would pay that much for such a part. I have bought similar units in very good used, and NOS (new old stock) condition for $15-$20 in the last year from eBay. I consider $15 for a part like this to be a good deal, but 4 times that is exorbitant. I imagine the seller is thinking that he will sit back and keep it listed until someone buys it. Perhaps someone will.

This week, 3 really good parts arrived in my mailbox, all manufactured by the National Radio Company. The first 2 were knobs and skirts, fitted with 5:1 “Velvet Vernier” reduction drives. These planetary friction drives operate smoothly, and look good too. The first one came in a really cool box. It’s in fantastic (unused) condition and was still in it’s box –

A view from the rear –

The big manufacturers such as National, Hammarlund, EF Johnson, must have produced huge numbers of their parts, yet it still boggles my mind that there still seem to be quite a few sitting around in NOS condition, never having been used before. It is a thrill to incorporate these parts into a new project, and is one of the factors that drives me to carefully plan anything before building it. I want these remaining parts to be used in something worthwhile.

The other knob and Velvet Vernier drive was even more impressive. It was so clean, bright and shiny, my friend commented that it could have been manufactured yesterday. I agreed. It really looks that good –

The reduction drive looks like it is made from stainless steel, which contributes to it’s shiny, new look. It even came with 4 original stainless steel mounting screws, in perfect condition, one of which has a pointer head for placing at the very top of the numbered skirt.

Here’s the same part from the back. I was gobsmacked when looking at this for the first time. It could indeed have been made yesterday –

A couple of days later, another knob and drive I have been wanting for a while arrived. As a teenager, a local ham gifted me several large boxes full of tubes, chassis, and assorted parts. Among them was the famous National HRO dial, coupled with an NPW-0 gear drive. The NPW-0 was the one in which the shaft that was coupled to the variable capacitor was perpendicular to the front panel.  I’d spent plenty of time as a teen admiring that dial and gear drive, but I lacked the skills and tenacity to incorporate it into a project and to this day, I don’t really remember what happened to it. My parents probably committed much of my parts stash to the trash after I’d been in the US for a few years and they’d figured that I most likely wasn’t coming back for it.

The unit that arrived in the mail a couple of days ago was the famous HRO dial, this time coupled with a gear drive that has an output shaft parallel to the front panel.  I wanted one of these because the internal mechanism is much simpler, consisting of just a split gear and a worm drive (the other type uses six gears). A nice variable capacitor came with it, which measured at ~15-245pF. It will make a good, accurate band-setting capacitor. I am not yet sure how easy it would be to use this drive with a different variable capacitor, or if I am “stuck” with the one attached to the unit, but using the attached one will simplify the physical construction of a receiver somewhat –

The vague plan right now is for this HRO dial and drive to end up in a regen (what else!) I was even thinking of having two identical ones – one for accurate bandsetting, and one for the bandspread, though that might be overkill. I have been doing some thinking as to what, if anything, my next regen should be. I haven’t built many regens and don’t think I will become one of those enthusiasts who builds many dozens of them. I don’t have a lot of regens to compare The Sproutie with, but I don’t think that regen performance gets much better, with the possible exception of the circuits that are at the very cutting edge of modern regen research (yes, there is such a thing). The Sproutie is fantastic for AM SW listening, being both sensitive and stable, with a regeneration control that slides smoothly into oscillation. SSB reception is a little trickier but from what I’ve been reading, it shares this in common with most (if not all) regens. I’m curious about tube regens but have doubts as to whether even a good tube regen would have better performance than a well-designed and constructed solid state one. NOTE – If anyone has experience or thoughts on this subject, I would very much like to hear them.

So I’m rather stuck, as I think that with The Sproutie, I may have stumbled upon a regen architecture and circuit that works particularly well and is convenient to use. The coils are easy to wind, as there is no separate tickler tap/winding, and the regeneration is smooth. This exact same circuit was used in the WBR. The WBR achieved it’s high oscillator/antenna isolation through the use of a balanced tank circuit. The Sproutie achieves it through the use of an RF stage, so there are no problems with common mode hum, a malady often experienced with designs that don’t employ an RF stage. You won’t experience issues with microphony either, if you build it sturdily (that part is up to you!) I can’t see why I should even experiment with other circuits, unless they are likely to offer a substantial improvement.  Circuit-wise, the only thing I’d quite like is a bit more audio power, so that I can really pump audio into a separate speaker for those occasions when receiving a strong and quality signal.

These are the features I’d like for my next regen (if it ever gets built) –

1) One or two National HRO Dials and drives

2) A bit more audio power for driving a decent external speaker to room-shaking volume

That’s it really. My Sproutie is that good. I am looking for an excuse to use this beautiful HRO dial in another regen, and cannot think of any substantial circuit improvements. Sure, I could build a tube regen but if it’s not going to perform any better, what’s the point? I know they glow, and that alone is cool, but I need a little more of a reason than that.

Thank you for letting me think aloud, and share some gratuitous pictures of my new vintage parts acquisitions.





January 12, 2015

A Crowdfunded Si5351 Breakout Board From Jason NT7S

Followers of Jason NT7S’ blog “Ripples In The Ether” will know that he has been experimenting with the Si5351 chip.  This little $1.50 (or cheaper) device is a PLL clock generator which provides 3 independently programmable outputs from 8KHz to 160MHz. While it’s phase noise is not quite as good as the Si570 (the chip used as the frequency-determining element in the Elecraft KX3), it’s a whole lot cheaper, and indications are that it’s performance will be easily good enough  for many rigs. There was some talk over on the Minima mailing list about using it in a version of Farhan’s new open-source transceiver project, The Minima.  At less than $1.50 for the device, you can imagine how useful this could be as the frequency determining element in a whole new generation of QRP rigs.

Jason talks about it at length on his blog at http://nt7s.com/

Enter the Etherkit Si5351 breakout board –

An earlier version of the Etherkit Si5351 breakout board. The crowd-funded version will omit the broadband output transformers T1, T2 and T3 in order to keep costs down. (Photo courtesy of NT7S)


To make experimenting with this chip even more tempting, Jason is crowd-funding a run of these Etherkit Si5351 breakout boards. More details here. As this blog-post goes to press, the Indiegogo campaign, which was launched earlier today (Sunday) has already reached it’s minimum goal for funding. It runs until Feb 10th. Show your support for Etherkit!

Join Jason’s Indiegogo campaign here!

January 7, 2015

Does The Sproutie Regen “Work” On SSB and CW?

Since building The Sproutie a few months ago I have had a great deal of fun with it. It is only the 4th regen I have ever built, but it is the best one so far. One of my main motivations for building it was to own a “serious” regen. I have long thought that the main reason this type of receiver is not taken more seriously nowadays is because they are rarely taken seriously when being built – and perhaps even designed. Kit designers are forced to make severe compromises because, well, who is going to pay hundreds of dollars for a high quality regen kit? A few of us would, but probably not in large enough numbers to make such a kit economically viable.

As an example of taking things seriously when building a regen, take a look at this build of NR5Q’s “Ultimate Regen” by Jim K4XAF.  Now that is a receiver any avid SWL would be proud to own and operate.

To make a long story short, I wanted to prove to myself that a regen could serve as a useful and valuable listening tool.  I was mainly concerned with SW AM broadcast stations as my main station rig, a K2, doesn’t have general coverage receive. For AM shortwave listening, The Sproutie is indeed very usable, and definitely more than just a novelty. I had spent very little time or effort listening to SSB and CW, and my initial impressions were that CW reception was fine, but SSB reception was occasionally good and occasionally not. I didn’t really think about why, and thought that perhaps it was something to do with the design that I didn’t understand.

Recently, I spent some time with The Sproutie on the ham bands, and the obvious finally occurred to me. It works fine on SSB but when the input signal is too strong, the oscillator pulls, resulting in FM’ing of the signal. In order to overcome this, the best way to operate The Sproutie when listening to SSB is to run the AF gain at, or near, maximum volume, and use the RF gain to set the desired volume. This will ensure that on strong signals, the RF gain is kept down. This is counter-intuitive to anyone who is used to operating a modern receiver with a product detector, where the modus operandi is usually to keep the RF gain at, or close to max, while using the AF gain to control the volume. However, if you got your start with SSB by using an older receiver that had a diode detector and was primarily designed for AM, you’ll remember that controlling the amount of BFO injection was fairly important in resolving the SSB signals well. With one of my first radios, a British R-107 WW2-era military receiver, I was taught to keep the AF gain turned up, and to control the signal-to-BFO ratio by adjusting the RF gain. On strong signals, I quickly learned to keep the RF gain down so there wasn’t too much input signal for the amount of BFO signal. With The Sproutie, the principle is the same, except you are limiting the amount of input signal so as to not cause the oscillator to pull. Those who have built and operated a number of different regens will be able to comment on this, but my sense is that this is a very common issue with them. Perhaps some designs minimize the effect of oscillator pulling. Can anyone more experienced than me comment? (Note – qrpgaiijin did. Please see his comments below this post on the reasons for oscillator pulling in regens. Input from experienced builders is very valuable so if you’re interested, please do take the time to read.)

Also note that another technique you can use to prevent oscillator pulling on stronger signals is to increase the amount of regeneration. On weaker signals, you might want to reduce the amount of regeneration closer to the “critical” point of onset of oscillation.  At that point, sensitivity is greater, which will help with the weaker signals. Of course, all these adjustments will affect the tuning, so you will need to adjust for that. It’s all part of the fun of operating a regen!

To sum up, The Sproutie does indeed resolve SSB signals well, but it requires much more attention and input from the user than other receiver architectures do. The “sports car with a stick shift” analogy works well here. When tuning the bands for SSB signals, you need your hands on the controls on a much more regular basis than when tuning AM signals. Listening to a QSO with stations of vastly different signal strengths can be an exercise in user attentivity and engagement.

By contrast, listening to AM stations on this receiver is much easier. If the oscillator pulls a few 10’s of Hz on strong AM signals (which it almost certainly does), you’re not going to hear the effects. It’s still a good idea to run the AF at a high gain setting so as not to overload the detector, but the need for this is nowhere near as critical. In fact, listening to AM stations on this little gem isn’t much more work than doing the same thing on a superhet. Although the precise regeneration point varies with frequency, you don’t need absolute maximum sensitivity when scanning the band for signals. When casually tuning a SW BC band, I can tune several hundred KHz before roughly resetting the regeneration control. Only when I find a signal I want to investigate further do I take the time to set the regeneration more precisely.  It’s a process that becomes second nature after a while. I can almost imagine the diehard regen users in the 1930’s deriding owners of the newer superhets, as they were too easy to use and “not real radios”. What’s the betting that happened?

So here’s the deal – The Sproutie does indeed receive SSB just fine, but you’re going to have to put a bit of work into it. It is, after all, a sports car with a stick shift, and not a luxury sedan with an automatic transmission:-)

NOTE – I just read the original article in Electric Radio magazine, describing NR5Q’s “Ultimate Regen”. There is, of course, no definitive word on whether it is indeed the best regen out there, but I took heart from the following quote by Bruce,

“Before we go any further, if you are a SSB operator you may be wasting valuable time. While I listen to SSB all the time on my ‘regens’ I would not want to try to operate a SSB station using nothing but a homebrew regenerative radio – that would be an exercise in futility.”

The above quote comes from a gentleman who built over 60 regens and authored many articles in the pages of Electric Radio. His words mirror my experience with The Sproutie, and further cements my belief that, as far as regens go, this one is pretty darned good. I love listening to AM on it, really like listening to CW on it, and although I can listen to SSB on it with little difficulty, I’d rather listen to SSB on a superhet with a product detector.

Apologies if you’re viewing this on a low-resolution screen, but I have an affinity for nice large pictures of radio sets.

January 6, 2015

7.28MHz Ceramic Resonators Arrived – Test Results

About a week ago, Joel KB6QVI, tipped me off to the fact that Cecil K5NWA was selling 7.28MHz ceramic resonators on his online site, The Parts Place. Enthused, we both ordered some, and both our orders arrived yesterday. Joel slipped his into a test circuit, which gave him coverage of 7.015 – 7.236MHz. He used a similar circuit to the one I used, though I don’t know his exact component values. Here’s the test circuit I used, which gave me a coverage of 7.080 – 7.268MHz –

Test circuit for the ceramic resonator. The transistor can be any low signal NPN type, such as a 2N2222, 2N3904 etc.


Adjusting the values of the 470p and 270p capacitors to, say, 330 and 270, or both to 330, should give a higher maximum frequency.  If I were using this in a simple rig, such as a Micro 40, Beach 40, or similar, I’d be using varactor tuning.  The 1N4001 (the “poor man’s varactor”) can have a minimum capacitance of as little as 5pF with an 8V bias across it, which would help too. It looks like it could be a useful component for simple 40M phone rigs and with a bit of experimentation, I bet I could increase the maximum frequency and get it close to the top of the US 40M band at 7.3MHz.  If you’re in a part of the world in which your 40M band ends at 7.2MHz, then some extra parallel capacitance should do the trick. It’s a 3-pin resonator. If the center pin is grounded, then the internal capacitors are placed in parallel with the resonator. Ignoring the center pin and connecting to the 2 outside pins only, leaves the internal capacitors out of circuit, increasing the maximum frequency.

If you have any interest at all, it wouldn’t hurt to stock up on a few. Resonators for frequencies like 3.58MHz seem to always be in plentiful supply, but ones with frequencies that are useful for the phone portion of 40M are harder to come by. Who knows how long these will be available for?

PS – as I mentioned in the previous post on this subject, these resonators are also available from Mouser, both in the US and the UK. Thanks to Steve G1KQH, for the tip. Here’s the link to them on Mouser’s site. If you set the site to the country you are in, then the link will show you the resonator on the Mouser site specific to your location.


December 30, 2014

New Source Of Resonators For 40M

Yesterday, Joel KB6QVI, tipped me off to a new source for ceramic resonators that look as if they should be a godsend for anyone building a simple QRP rig for the phone portion of 40M (such as VK3YE’s Beach 40) – that’s if they perform according to specifications.  A while back, we both bought some Murata resonators with a specified frequency of 7.2MHz, only to find that the very highest frequency they would oscillate at was 7.15MHz. Cecil K5NWA runs an online parts site called The Parts Place, and is listing a 7.28MHz resonator. The description says,

“Tunes over a wide frequency range. With 100 pf capacitor a shift of 7036KHz – 7284KHz is expected – will verify when parts arrive, do not use the center pin.

Note that for a lower top frequency, put a fixed small polystyrene capacitor in parallel with the adjustable capacitor, which can be made smaller.”

Joel and I ordered 20 each, and Patrick W9PDS said that he was going to purchase some as well. When Joel first found them, there were 167 available – there are now 127* as I write this.  They are 30 cents apiece, 22 cents if you buy 10 or more, so it would seem worth picking up a few for the parts bin, as resonators that are usable in the upper portion of 40m don’t come along too often. The last time we found good ones was from hamshop.cz, and they have been out of stock for months now.

Please note that we haven’t yet received ours and don’t know whether they will resonate reliably within a usable range of frequencies but for home-brewers, this is worth a try while they’re available. If they are indeed usable, let’s hope that Cecil is able to get more in once the current lot is sold out. Incidentally, Cecil’s site is easy to use. I received e-mail status updates to verify that the order had been received, then another one to verify that payment had been received, and another one to notify that the order had been approved – all in short order. I assume that there will be another when the order has shipped. With a business like this, being run by an individual ham, this level of notification already surpasses what I would expect.

My soldering iron hasn’t been seeing much action lately, but Joel is an inspiration at the workbench; I have lost track of the sheer number of projects he has put together since I have known him. Doubtless he will verify that these are usable for ham applications once his arrive and I’ll post the results here once that happens. If I happen to put one of mine into a test circuit, I’ll let you know what happens with that too

Here’s the link once again (opens in a new window), and thank you to Joel for bringing this to our attention.

*As of 16:25 UTC (8:25am PST), there are now just 88 available.

NOTE – Steve G1KQKH, in the comments below, noted that this same resonator is available from Mouser. Check the comments section for his link to UK Mouser. If you’re in the US, the link is here (opens in a new window).

December 7, 2014

Thomas Witherspoon K4SWL Joins The Friends Of The Shortwaves!

I just knew that at some point, Jeff K1NSS would include Thomas Witherspoon, K4SWL in his Friends Of The Shortwaves series on Dashtoons. It was a no-brainer. Thomas’ blog, The SWLing Post has a very strong following and Thomas continues, through the blog, to make a strong case for the continued use of shortwave broadcasting the world over, and to support the interests of shortwave listeners.  He also hosts an online archive of shortwave recordings at The Shortwave Radio Audio Archive. If that wasn’t enough, as founder and director of the charitable organisation Ears To Our World, he puts self-powered shortwave radios into the hands of people in areas of the world that are under-served by the forms of mass media communication that we enjoy in the developed world. Thomas doesn’t just talk the talk – he walks the walk as well.

If you need the services of an experienced and talented artist who also “gets” the ham community (as he is himself a ham), you should seriously consider Jeff Murray K1NSS. Many people have used his services, and you’ll see many examples of his work at Dashtoons.

November 23, 2014

Videos Of The Sproutie Regen In Action

Many apologies for taking so long to get these videos up. The only camera I have that can do video is so old and gives such poor quality video, that it’s a little tough for me to feel inspired in that direction.  I do like to put quality still pictures on my blog, and am currently unable to do justice to my projects when it comes to videos.  However, even a low-res video can still give you an idea of how a receiver handles that no amount of still pictures can, so last night and this morning, I made a few brief videos, and here they are. I would recommend viewing them on this page rather than on YouTube, simply because there is no point in seeing the larger version on YouTube – the video resolution simply isn’t there. Aaron N9SKN is building a Sproutie, and asked if and when I was going to post videos. His request gave me the final push/feeling of guilt that was needed to get me moving!

Here’s The Sproutie receiving CW and SSB on 20M (with the coil that tunes from 12100 – 14400KHz) –

and here it is receiving AM stations on the 60M and 49M BC bands (with the coil that tunes from 4810KHz – 6320Khz) –

As the main blog-post on The Sproutie shows, I have coils for continuous coverage from about 3MHz up to 16MHz (as well as a coil for 2.1 – 2.7 MHz) and have wound temporary coils that worked up to 24MHz. It will probably work even higher. I have even read reports of Nicky’s TRF (which is the circuit I used for The Sproutie’s front end) being used successfully on the 10M amateur band!

The original blog-post giving construction details of The Sproutie is here.

September 16, 2014

New “Free” SA602 and SA604 Offer Back – Now With Overseas Shipping

Filed under: Amateur Radio,Ham Radio,QRP — AA7EE @ 6:29 am
Tags: , , ,

On Saturday, a medium size Priority Mail flat-rate box packed full of IC’s, resistors, transistors and other devices arrived from KV7L. Lynn is the gentleman who made my previous SMT SA602 and SA604 offer possible by shipping me 2 large rolls of SMT SA602’s and SA604’s a few months ago. At a rough guess, that initial shipment contained about 1700 SA602’s and a few hundred SA604’s. Almost all of them went to QRP clubs wishing to sell them to raise funds, people organizing group builds, and the parts bins of individual home-brewers – and all for $4 to cover just the cost of shipping and the Paypal fee.

Now I have another, final shipment from Lynn and can open up this offer again. As well as the SMT 602’s and 604’s, Lynn threw in some bags of 2 and 3 W resistors, some of which will be useful for making QRP dummy loads, as well as some voltage regulators, power MOSFETS, and small signal NPN transistors. A number of people did ask if I could ship overseas, to which I replied that I was trying to keep the distribution process simple (for me) by limiting it to the US only. This time around, I’ll open it up to other countries, though the shipping costs are significantly higher and I’m not sure whether it will be considered worthwhile to those not in the US.

Sprat The QRP Cat wasted no time in thoroughly smelling all the parts. Lynn has dogs so I’m sure there was plenty for Sprat to sniff –

Before detailing the new deal (boy, I feel a little like FDR :-) ), there was something else I wanted to mention. Lynn KV7L said to me on the phone that he’d really like to receive QSL’s from some of the home-brewers who have had some of the parts from him so he can get an idea where his parts are ending up. Although I wasn’t shipping overseas in the last round, one gentleman in India asked if I could ship to a friend in the US who was visiting him in Bangalore in the near future and could deliver the parts. He is an educator who will be using his 602’s to encourage his students to build something. Lynn said he’d love to have a QSL from India, and from all the other places his parts are going so that he can put them up on his wall and get an idea of how his parts are being distributed far and wide.  This is not about tracking them – it’s because Lynn’s only involvement  in this giveaway has been to very kindly ship the parts to me, while I distribute them. He is a bit disconnected from the process and being able to look at QSL’s on his wall will help him feel a bit closer to the whole “free parts” operation. If you have already received parts from him (through me), I know that he’d love to receive a QSL from you. You can either send it to him, or to me – and I will forward it on to him. Both of our addresses are good on QRZ. Lynn’s address is a PO Box, while his actual QTH is in a fantastic radio location. He is miles from his nearest neighbor in rural Eastern Oregon,  and not served by any utility (he is 100% solar-powered). He has 5,000 feet of wire buried in the earth for a ground and his resulting noise level is very low indeed. He is the co-net manager of the Noontime Net on 7268.5KHz daily. It’s a regional net that covers most of California, Oregon and Washington, as well as a few other nearby states when daytime conditions are good and it seems that Lynn, with his fantastic radio location, hears almost everyone who calls into the net.

If you haven’t yet taken advantage of this offer and would like to, please know that Lynn would love to receive a QSL from you as well.  I think it’s a very modest request from a gentleman who has shipped me something like 2,300 SMT SA602’s and 600-800 SA604’s and asked for nothing in return, other than the occasional update on how the giveaway is going. If you don’t have a QSL then don’t worry about it – and please don’t let it deter you from taking advantage of this offer.

This time around, as well as SMT SA602’s and SA604’s, I have a bunch of 1 and 2 watt resistors in low values, some of them suitable for building QRP dummy loads. There are some 160 ohm resistors and some 130 ohm ones. 2 x 160 ohm and 1 x 130 ohm resistor, all in parallel will give you a total effective resistance of 49.5 ohms. If all 3 resistors are 2 watts, then the final dummy load will handle about 6 watts, which is more than enough for the QRP “full gallon” of 5W. Some of the resistors are 1W, and even if you were to use just those, your final dummy load would still handle 3W,  There are also other values of 1 and 2W resistors such as 22 ohms, 27 ohms, and also 51 ohms. I don’t have many of the 51 ohm ones, so you’ll probably only get one of those, but there are more available of the other values.  Actually, the 51 ohm 2W resistor would make a useful dummy load on it’s own. It should handle 5W for very short periods and of course, if your TX is just 2W, it will be even more able to handle long key-down periods. If you want to make a “classic” QRP dummy load, you can mount your decided combination of resistors in a mint tin, along with a BNC connector for connecting it to your TX and you’ve got yourself an affordable and useful station accessory.

I also have some LM2575T 12V 1A voltage regulators, in a 5-lead TO-220 package. Datasheet here. There are also some F10P03L P-channel power MOSFETS, datasheet here, as well as some PN4275 NPN switching transistors, for which the datasheet is here.  I may throw in a few general purpose NPN transistors too, if I have any left. They have the number F15103477844 printed on them which I haven’t been able to find any datasheets for but that is not surprising. It is very common for mass-manufactured electronic goods to use parts with parts numbers that were supplied specifically for one production run. They are small signal NPN transistors and they may well be very similar to transistors used in many other products, that had different numbers stamped on them. They’ll most likely work fine in many circuits that call for 2N3904’s, BC109’s or similar.

This photo isn’t exactly what you’ll get in your package, but it’s pretty close. You’ll probably get this, along with a few extra resistors and possibly some extra transistors thrown in. As a bare minimum, you’ll get 15 x SMT SA602’s, 6 SA604’s, an assortment of 2 and 3 W resistors in low values, some of which will be suitable for making up QRP dummy loads, 8 x LM2575T 12V 1A voltage regulators, 6 x F10P03L P-channel power MOSFETS, and a small handful of PN4275 NPN transistors –

My supplies of both 602’s and 604’s are now limited but if you need a few extra for a club project or group build, please ask and I’ll try to accommodate you. The 602’s are particularly limited, but I have a few more of the 604’s, so if you have a group project that uses 604’s, I should be able to provide them.

The last offer was just for 602’s and 604’s and for that I was asking $4. To ship these I need a small box, (as opposed to the padded mailer used previously), which costs a bit more, and the extra weight costs a bit more in shipping, I am now asking $6 payable via Paypal for US builders – and also asking if you can send KV7L a QSL card (either directly to him, or to me so that I can pass it along to him – but don’t write it out to me – write it to Lynn KV7L). If you don’t want to use Paypal, you can mail a check for $5.50 (because I don’t have to pay the Paypal fee) to me. This is quite a handy way to do it, as you can include your QSL card for Lynn in the envelope with the check :-)

Whatever you do, don’t send any money until you have first e-mailed me! My e-mail address on QRZ is good, or you can use mycallsign@arrl.net

If you are anywhere in Europe I will now ship to you, but the shipping costs are significantly higher, I’m afraid.  If you are in Europe, I need to ask for US$17 to cover the shipping box, shipping costs and the Paypal fee. I’d rather not accept personal checks from outside the US, so will have to ask for Paypal for non-US builders, to keep the process relatively simple for me. However, if you are outside the US and are able to mail a QSL card to Lynn (either to Lynn, or to me – but make sure it is written out to Lynn) I will be happy to reimburse you for the postage via Paypal. I’d really love for Lynn to get a whole bunch of QSL’s from many different areas. He’ll love that. In fact, if you’re a US builder who is paying via Paypal, let me know if you plan to send a QSL and I’ll knock 50 cents off the price to cover most of your postage.

If you are outside the US and Europe, I may well be able to ship to you, but will have to get a quote from my local Post Office. It will probably be very close to the price for EU. E-mail me if you seriously intend to take advantage of the offer and I’ll get a price for you.

I hope that all made sense, and that the parts make it worth the expenditure of a few dollars for the shipping. It’s a no-brainer for US builders, and may be worth it to non-US home-brewers too.


73 for now,

Dave  AA7EE

PS – I have 100 of these Molex connector shells. The total width is 1  1/8″  (1.125″). Let me know if you’d like some of these too, but you have to ask as I know that most people won’t want them.

Update (Sep 18th) – I am out of all the transistors and the voltage regulators but do still have a few SA602’s, resistor packs, and plenty of SA604’s left. At this point, I can still make up a package for you containing SA602’s, SA604’s and the resistor pack. Prices are the same (as the shipping is very nearly the same).

Update (Sep 22nd) – I have a good amount of SA604’s left, a few SA602’s, and the Molex connectors. Everything else is gone.

Update (Sep 24th) – All that is left is the SA604’s and the Molex connector shells.

August 30, 2014

SA602 and 604 Giveaway Update, and SA604 Circuits

Filed under: Amateur Radio,Ham Radio,QRP — AA7EE @ 6:04 pm
Tags: ,

I’ve had a busy few days. Since posting details of the reels of SMT SA602 and SA604 IC’s that a very generous ham sent to me with a request to distribute them to other homebrewers and building groups, I’ve been spending quite a lot of time cycling to and fro between my house, the local print and copy shop (for supplies of padded mailers), and the Post Office. The first day’s worth of envelopes looked like this just before being bundled into my backpack for the short trip to the Post Office (names and addresses inexpertly blurred out in order to protect the identities of the innocent) –

I mailed out 18 packets on the first day, and almost as many the next day. Most went to individual builders and experimenters, though a few did go to groups for group builds. The response has been very encouraging. I wasn’t too sure how many people would be interested in SMT parts but it seems that quite a few folk do indeed experiment and build with them – and they are not all young ‘uns either. One gentlemen who requested a set is 83 years old. Excellent! With the help of breakout boards, like W1REX’s MePADS, or these ones from OSH that Sanjay KI6VFH told me about (only $1.50 for 3, including shipping), once you’ve got the device mounted to the pad, building Manhattan-style with these IC’s is straightforward. Incidentally, the boards from OSH are SO-8, so will work for the 602’s but not the 604’s, which are SO-16. Also, Rex’s pads can be glued straight onto a copper substrate as there are no contacts on the flipside, while the OSH one will need to be suspended above the copper groundplane with short, stiff ground leads. Perhaps someone has posted a design for an SO-16 breakout board on OSH?

Standing in line at the Post Office has it’s good sides, one of them being the notices that I spotted attached to the plexiglass divider at the customer service counter –

As I thought would be the case, everyone wants the 602’s. I was expecting only a few people to also want 604’s but as it turns out, a majority are also asking for a few of them. Many don’t yet know what they will do with them but are hoping to find a worthy project. A few actually have projects planned. One gentleman is planning a group build with his club, in which they will build pagers. I didn’t ask for more details on what the frequency of operation will be, but I am curious. Another is going to build a weather satellite receiver.  Paul K0EET mentioned that 604’s turn up in home-brew spectrum analyzer projects as an IF strip and a logarithmic RSSI (to drive the y axis).  He also told me about an article in the July 1993 issue of QST by OH2GF for a synchronous AM detector using an SA604 and a couple of 602’s. It is designed for receivers with an IF of 450-455KHz, so would be a great addition to many existing shortwave receivers. Thanks Paul (makes mental note to remember this project). In it’s application as a Received Signal Strength Indicator (RSSI) it could also be used as an S-meter for a direct conversion receiver (a quick Google search should get you a circuit).

So quite a few circuit ideas for the SA604. The application sheet also shows how, with an SA602, you can make a simple FM receiver. Personally, I can see wanting to try it out as a synchronous detector for AM signals at some point.

Oh – one idea for the 602’s which I thought was very novel, was one gentleman who plans to rip out the guts of his HW-8 and replace them with a DDS-tuned superhet. Cool!

I started out with quite a large reel – bigger than shown in the picture of Sprat The QRP Cat performing QC. By the time I took that picture, several hundred had already gone out to various experimenters and builders. With the encouraging response to these posts, I will probably run out soon. Not to worry though, as the gentleman who sent them to me still has some left that he has promised to send. I am not sure when those will arrive, but I’ll post updates to this blog. I don’t think it will be very long.

If you build something cool with these chips, please let me know!

NOTE – SA602 and 604 offer on hold until further notice. I’m almost out, but the very kind gentleman from Oregon who sent me this batch has some more he will be sending soon. I will make a new post to this blog when I have more IC’s in stock.

August 26, 2014

Free NE602’s and 604’s

Filed under: Amateur Radio,Ham Radio,QRP — AA7EE @ 8:29 pm
Tags: , , ,

It’s been on my mind to make this post for quite a while now. Some time back, a very generous ham in Oregon gave me a sizeable quantity of SA602 and SA604 SMT IC’s. They were part of a production run that didn’t materialize. He got a deal on them and has been hanging onto them ever since. Now he would like to pass them on (for free) to other home-brewers, so he asked me to help out. He wants them to go into the parts bins of people who may well use them, and does not want them to go to people who will merely resell them for a profit. He’s perfectly OK with them being used for a club group build, or a club kit designed to raise funds for a QRP club – just not in large quantities to individuals who will turn around and sell them. The idea is to encourage people to build something.

I’m sure you know all about the NE602/SA602/NE612/SA612 oscillator and double-balanced mixer IC. It has, of course, been used in countless numbers of simple direct conversion receivers such as The Sudden. It’s not ideal in the front end of a receiver, being very susceptible to overload in that usage, but it sure does make it easy to build a very simple DC receiver.  It can be used to good effect as the 2nd mixer in a receiver, and as a balanced modulator. In any application where the input levels are within certain defined limits, it performs well. The SA604 is a low-power FM IF chip. I’ll leave you to do the research and check out the datasheets.

Oh – and these IC’s have been through rigorous quality control. Here’s Sprat The QRP Cat checking the roll of SA602’s. They passed the test :-)

Sprat The QRP Cat performing quality control on the roll of SA602’s.

The SA602’s are in an SOIC-8 package and the SA604’s in an SOIC-16 package. Here is one of each, placed on a sheet of W1REX’s MePADS –

Jason NT7S built a really neat SSB rig based around an Si5351 PLL/VCXO chip. He used 2 of these SA602’s as part of the design. you can read about (and see) Jason’s “Simple SSB” rig here. He describes the rig’s architecture in an earlier post here. It’s great stuff and very much in the spirit of ham radio.

I don’t want to make any money from this, but would like to cover my expenses, so I will charge a small fee to cover the cost of a padded mailer, postage and the Paypal fee. Here’s the deal. If you are an individual home-brewer in the continental US who could use some of these SA602 SMT IC’s (which are exactly the same as NE602’s), send me an e-mail – either to my e-mail address on QRZ, or to mycallsign@arrl.net to let me know you’re interested. I’ll reply to let you know what e-mail address to Paypal the money to. For $4, I’ll send you 15 SA602 IC’s. If you’d like some SA604’s as well, let me know but please only ask if you think there’s a chance you might use them.  If you would like a larger quantity for a club kit or group build, send me an e-mail with the info and I should be able to help you out.

Oh – and unlike my recent variable capacitor give-away, I have quite a lot of these, so you don’t need to be the first (or even the 20th or 30th) person to reply. As not too many builders use SMT, I suspect this offer will be available for a while.

I am very grateful to the gentleman in rural eastern Oregon who is the reason for me to be able to spread this little piece of home-brew goodwill!

NOTE – to the gentlemen who left comments, I have deleted them. It occurred to me that having your e-mail addresses and info in the comments section might cause some enterprising scammer to pretend he/she was me and ask you to send the money to them. Having said that, they would have to be pretty desperate to go to all that trouble to make an extra $4!  Best to e-mail me at my e-mail address on QRZ, or to mycallsign@arrl.net

NOTE – SA602 and 604 offer on hold until further notice. I’m almost out but the very kind gentleman from Oregon who sent me this batch has some more he will be sending soon. I will make a new post to this blog when I have more IC’s in stock.


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