Dave Richards AA7EE

October 20, 2017

The Manhattan Projects of Bob W3BBO

Bob W3BBO and I have been communicating via e-mail for a couple of years now, and I’ve been meaning to write this post for quite a long time. I’ve been on hiatus from home-brewing, and expect to be in the future too. The brief run of Manhattan projects I built was really fun, but I seem to have scratched that particular itch. About 7 years ago, I began dabbling in micro broadcasting under the FCC Part 15 regulations. I did quite a lot of work on the automated programming for my little music station but the transmitter, on the AM broadcast band, didn’t get out for more than a couple of hundred feet. Recently, I revived my pursuits in this direction, and have had considerably more success, being able to hear my little station over a wider area than before. It’s an ongoing project and at some point I may blog about it, though little homebrew is involved I’m afraid.

Back to the subject of Manhattan construction. Bob W3BBO, has been a ham since 1955. Though a self-described “appliance operator” for much of the early part of his ham career (me too!) he did build a few things along the way, mostly using “ugly” construction. His biggest project was Ted Crosby’s HBR-14 receiver, described in several issues of QST, beginning in the late 50’s and spanning over several years, as well as in the 17th edition of The Radio Handbook. I’m envious – the HBR-14 is a significant homebrew achievement!

Bob says that shortly before his retirement, when living in New Jersey, he was introduced to the technique of Manhattan construction by the NJQRP Club. He says that most of his projects worked, but didn’t look too good. That reminds me of my first forays into Manhattan – I was in exactly the same boat. My projects mostly worked, but they looked fairly ragged and haphazard. Nothing wrong with that, of course – it’s a classic homebrew look 🙂

After reading this blog, Bob’s interests turned to regens and he had a go at building a Kitchin Scout beginner’s regen, using the MePADS and MeSQUARES from Rex at QRPMe. (Incidentally, for builders who like particularly compact layouts, or want to try working with SMT, Rex now has smaller pads, called STIX.)

Look at this – a homebuilt PCB chassis, Manhattan construction, and Dymo labels. A perfect homebrew combination! –

W3BBO’s Kitchin regen. Photo courtesy of Bob W3BBO

Bob sprayed the boards with a thin coat of clear Krylon spray –

W3BBO’s Kitchin regen. Photo courtesy of Bob W3BBO

It sure looks good, but Bob revealed in later e-mails that the performance left something to be desired. After talking with John WA6TLP, he decided to rebuild it using a J310 FET for the oscillator/detector instead of the bipolar transistor that was in the original design. As you know, I’m quite fond of regens, and I think a lot of people underestimate them. A few times, I’ve heard comments along the lines of, “I built a regen once. It was fun, but it didn’t work that well.” Or I hear a declaration that regens aren’t “very good”, and I think to myself that this must have been based on an encounter with a set of subpar performance. Luckily, Bob stuck with it, rebuilt his regen, and ended up with one that worked well. Some folk aren’t as tenacious though, and it bothers me that because of one bad experience, they might walk away with less than stellar impressions of this classic and frugally effective circuit architecture. I’ve heard a few folk say they built this particular regen and had trouble with it. If you did, you might want to read this, from John WA6TLP’s site. I’d like to emphasize that I have had no direct experience with this design. John is perhaps a bit blunt in his assessment of the performance of this circuit, but I’d rather have that type of candid approach than the subject not being broached at all and, as a result, a number of builders wondering what they did wrong – or first time regen builders being put off regens altogether. Also please note that this is not the same circuit as the Scout Regen supplied by QRP Kits (which Charles Kitchin also designed). Everyone I know who has built one of those has been happy with it.

Here is Bob’s modified Kitchin regen, per John WA6TLP. He said it took him a while to begin this one, due to his disappointment with the performance of the earlier build, but was very happy this time around. The signals from it, he said, nearly blew the headphones off, and the performance was much better –

Bob’s modified Kitchin Regen. Photo courtesy of W3BBO.

 

Bob’s modified Kitchin regen as seen from the rear. Photo courtesy of W3BBO.

Around the time that Bob began work on his modified Kitchin regen, he bid on, and won, a National N Dial on eBay. Boy, do I love the feeling of landing a quality vintage part! He’d had it in mind to continue his voyage of regen discovery by building his version of a Sproutie regen, and the National N Dial was the first major step towards that goal. With this goal in mind, the first task he accomplished was to build the audio board, with one of the preamp/filter stages. This particular filter had a very wide bandwidth. I called it a “straight-through filter” and because it has gain and such a wide bandwidth it is, in effect, simply a preamp. Using his modified Kitchin regen as the front end, Bob hooked it up and was able to verify that it was working –

The audio board for Bob’s version of The Sproutie regen. Photo courtesy of W3BBO

The audio board being tested. Photo courtesy of W3BBO.

Bob constructed the chassis from double-sided PCB material. He wondered whether it would be sturdy. Indeed, it is quite a large chassis for this type of construction, but he said that it was adequate, thanks to some judiciously-placed gussets –

Photo courtesy of W3BBO

With that National N Dial and chrome grab handles, it’s really beginning to look like a serious radio! –

The National N Dial gives Bob’s regen a classic look. Photo courtesy of W3BBO

At this point, the lack of a couple of shaft couplers for the tuning capacitors was holding Bob’s progress up. Luckily, he found what he was looking for at a local hamfest, and the “bones” of the regen were complete. Bob says that he likes the flexible couplers, as they allow for slight misalignment when mounting the dials and capacitors. He said that up to that point, mounting the tuning capacitors had been the hardest part of the project. I think very similarly. Building and drilling the chassis, and mounting all the controls is a major step. When I’m at that point, I feel as if I’m “over the hump”. It’s a bit like moving house – when you feel that you’re halfway done, you’re actually only about 33% of the way there! However, it gives you a big boost, because you can easily see how it’s finally going to look –

Tuning capacitors mounted. Photo courtesy of W3BBO

Then, one day, I received the following message from Bob –

Morning Dave,

I’m happy to say that my version of the Sproutie works!  WooHoo!

I left the 12 vdc line for last, hooked that up and then the smoke test.  Connected the antenna and applied 12 volts…nothing at first.  I started to turn up the regen control and after several turns, thought maybe I had something screwed up on the RF board.  Then…wham!  It burst into regeneration and I was hearing signals!  My fourth regen, but it is always a thrill…WOW!

I haven’t built the 700 Hz filter yet, just using the straight thru filter and using a coil similar to your 6880 – 7450, as it seemed simplest and it covers 40 meters.  I’m not sure of my coverage Dave, but I did copy some 40 meter CW and SSB signals a few minutes ago.  

Reading that e-mail from Bob, I knew exactly how he felt. Hearing atmospheric noise and signals from a receiver you built yourself is always exciting – especially those first few times with a new project. Here’s a view of the underside, showing the RF board next to the octal coil socket, and the main audio board underneath it. It is connected to a battery pack, and ready for listening –

A view of the underside of Bob’s version of The Sproutie regen, powered by a battery pack. Photo courtesy of W3BBO.

In this next shot, the empty board will be an extra filter. I believe it ended up being a 4th order, 2 stage 3 kHz filter, which gives a fairly gentle roll-off. Although a filter with a steeper slope would be more ideal for listening to SSB, the gentle roll-off of this filter means that AM SW broadcast stations also sound fine through it. It’s a good all-purpose filter for SW regen listening –

An empty board which was about to become a 4th order, 2 stage 3 kHz filter. Photo courtesy of W3BBO

Bob said that he didn’t detect any microphony, which is a testament to his short, stiff leads and overall solid construction. I didn’t experience any microphony in my original Sproutie either, but do get some in my Sproutie MK II. I think the much larger chassis has a natural resonance that causes it.

Bob housed his speaker in a separate cabinet, an arrangement that reminds me a little of the way that Jim K4XAF did it with his version of Bruce NR5Q’s Ultimate Regen.  Bob constructed his cabinet from a 1/2″ project panel that he picked up from Home Depot. In this photo, the cabinet is held together with brads, but still needs to be pulled apart, sanded, and painted –

The cabinet, before sanding and painting. Love the separate section for the speaker! Photo courtesy of W3BBO.

The last I heard, Bob really liked listening through the 3kHz filter, so his regen had just the so-called “straight-through” filter and the 3 kHz (2 stage, 4th order) one. I built my “straight-through” filter mainly for comparison purposes. Because it’s bandwidth is 20 kHz or more, you hear everything, including a lot of hiss and general static. Listening in such a way can be rather fatiguing after a while, so some kind of filter, even if it’s only to cut down on the hiss, can help make listening for longer periods much easier. Although an audio filter won’t do much for RF bandwidth, it can certainly help cut out interference from nearby stations on CW and SSB .

Here’s the finished cabinet. –

Bob’s finished regen. Magnificent! Photo courtesy of W3BBO.

Here’s how he stores the spare coils, on a drilled piece of wood. Simple and effective –

Coil storage for Bob’e regen. Photo courtesy of W3BBO.

Incidentally, if you want to take a look at some of Bob’s other homebrew projects, Larry W2LJ has featured some in his blog. In fact, he featured this very regen over a year ago. That’s how slow I have been on the uptake recently! I won’t give you all the links to Bob’s projects on Larry’s blog here, but a quick web search should help out. However, this 6L6 transmitter in particular, caught my eye. There’s nothing like a good-looking chassis with tubes mounted on it. You can see another photo of Bob’s very good-looking 6L6 transmitter along with it’s power supply, on his QRZ page.

Bob also built a direct conversion receiver with David Cripe’s Hi-Per-Mite filter (still available, as I write this, from 4SQRP) – as I did with my Rugster. Ever the capable homebrewer, he did a great job –

Bob’s direct conversion receiver using an NE602 in the front end, and a Hi-Per-Mite filter as the entire audio chain. Photo courtesy of W3BBO.

Bob recently acquired an HW8 in pristine condition. He was really impressed with the performance of this Hi-Per-Mite DC receiver, and said that his Heathkit rig could benefit from the addition of a good narrow filter like NM0S’ nifty design.

Bob’s direct conversion receiver using an NE602 in the front end, and a Hi-Per-Mite filter as the entire audio chain. Photo courtesy of W3BBO.

Though not a scratchbuilt homebrew project, while we’re at it, I’d like to show you Bob’s SST, which he built from a kit. I’m a little envious, because by the time I decided I definitely wanted to build an SST, the kit was no longer available in the US, and the Japanese company that was selling them was charging double the price, and wouldn’t ship overseas anyway. I had to scratch-build mine, and remained a little envious of those who had gotten in on the SST craze when it was in full swing, and the kits were available.

Bob painted his SST to match his PFR-3. Look at that beautiful paint job! –

Bob’s SST. Photo courtesy of W3BBO.

– and here it is alongside the PFR-3 and a few other matching goodies –

Lots of yellow! Photo courtesy of W3BBO.

Thank you for sharing some of your homebrew projects with me Bob. For any reader who is interested in seeing more, some judicious searching on Larry W2LJ’s blog should reveal more gems.

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11 Comments »

  1. Thank you, so much, Dave! I’ve always admired and have been envious of both yours and Bob’s home brewing skills. As much as I would love to be proficient at it; it just seems to not be one of my skills. Thank you for shedding light on Bob’s projects in a so much more informed and authoritative way then I’d ever be able to manage. And thank you so much for the posts on your own projects. They keep me inspired. 73 de W2LJ

    Comment by Larry W2LJ — October 20, 2017 @ 6:11 pm | Reply

    • Larry – your consistent dedication to our hobby over many years is something I can never hope to match. Your regular blog updates, support for QRP contesters, and the QRP community in general, is fantastic. We all practice and experience the hobby in different ways, and the QRP community is lucky to have you. A big thank you right back at you!

      73 for now,

      Dave
      AA7EE

      Comment by AA7EE — October 20, 2017 @ 11:49 pm | Reply

  2. Dave. It’s very good to hear from you again. I was beginning to think you might have turned on, tuned in, and dropped out!

    Here’s a thought – why not find a way to simulcast your low-power radio broadcast over the Internet as well as over the airwaves? Larger potential audience while still “broadcasting” over the air. Might be interesting!

    In any event, very good to know you’re still around – stay in touch!

    73, Jeff KE9V

    Comment by Jeff Davis — October 20, 2017 @ 7:48 pm | Reply

    • Great idea Jeff. It’s a music-intensive station and, unfortunately, the streaming and music licensing fees would be prohibitive. Keeping it as a micro-power terrestrial-only operation keeps it simple and affordable. Thanks for the good wishes – I’m still around. As some of the old-timers on my daily 40M net say, I’m still on the right side of the ground 🙂

      Comment by AA7EE — October 20, 2017 @ 11:53 pm | Reply

  3. I couldn’t agree more – the most difficult part of any home brew project is locating the variable capacitors. Not only is getting the screw holes in the right place without having to make the holes gigantic and then covering up the disaster with washers but getting the capacitor shaft to line up in the same vertical and horizontal as the reduction drive is also very character building. I have found mounting the capacitor on a separate piece of PCB and then hanging the capacitor off the back of the reduction and finally attaching the capacitor to the chassis with an aluminium bracket works. (PS you can temporarily attach the alloy bracket to the capacitor with a dot of super glue until you are happy with the fit.)
    Tony VK3CAB

    Comment by Tony Goldsworthy — October 21, 2017 @ 5:35 am | Reply

    • What’s that saying – measure twice, cut once? Well, I tend to measure about 10 times before I cut (or drill)! I love the picture of your shack on QRZ Tony – that’s the shack of a ham who builds things!

      Comment by AA7EE — October 22, 2017 @ 3:04 am | Reply

  4. Dave,

    I fell upon your blog inadvertently recently. Your terrific construction prowess is enviable. I did not realize the level of performance a regenerative receiver can have. My attempts with regens in the past have been less than inspiring. I have checked out Kitchin and other regen receivers on You Tube. (In fact, I find that I have some of his articles from 1990s Communication Quarterly in my files.)

    I am wondering if you have come across the RCA RA7 regen receiver. It was designed for the US Navy and was in use during WWII. This is how seriously the technology was taken. If you haven’t seen this already take a look at:

    The manual can be found at:

    http://bama.edebris.com/manuals/rca/ral/

    The receiver’s schematic is interesting. There are two tuned RF amps before the regen detector and there is a passive low pass filter (nick frequency c. 1300Hz) and a switched parallel tuned circuit resonant at 20 frequencies between 450Hz and 1300Hz.. Obviously, the filters are designed to optimize CW reception. The tuned RF amps are interesting. It seems that some decent RF gain is necessary to help with weak signal reception, as long as the gain can be wound back when not needed. All this is contrary to the more modern renditions.

    Anyway, thanks for your blog.

    Comment by Henry — October 24, 2017 @ 7:50 am | Reply

  5. hello i was a little surpriset.. a (((((( REAL )))))))reflex reciever. thanks for showing …..

    Comment by lm van der linden — November 6, 2017 @ 1:38 am | Reply

    • Regenerative receivers actually, but close. As I understand it, a reflex receiver feeds back just the demodulated AF into the input of the amplifier stage, so that the stage is amplifying AF and RF at the same time. A regenerative receiver feeds back the RF signal.

      Comment by AA7EE — November 6, 2017 @ 8:33 pm | Reply

  6. Very good to see the blog is still active, and inspiring with the posted projects. W3BBO’s work is very clean with some nice part layouts and case ideas. That is the only problem with this blog site Dave, there is so much beautiful work that I tend to forget what I came to look for. Thank you for all your efforts on this blog. 73 N8RVE

    Comment by John Morris (N8RVE) — November 20, 2017 @ 1:19 am | Reply

    • Hello John – and good to hear from you! Apologies for the lack of blog updates, but I can only report on what I’m doing, and I haven’t been doing much. Are you still building?

      Comment by AA7EE — November 20, 2017 @ 5:15 pm | Reply


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