I finally got around to putting up a video of the WBR Regen on YouTube. Unfortunately, I didn’t get many good recordings of SSB – this was mainly due to band conditions and the times of day that I was recording. However, it was time for me to get this thing out so that I can move on. First plan is take a break this weekend. I never quite know for sure what my next project will be or when it will begin. This is a hobby and I simply follow my interests:
Dave Richards AA7EE 
Dave, that’s not at all what I thought a regen would be like to tune. For some reason, I had it in my mind that the regen control had to be constantly adjusted as the receiver was tuned…that the “sweet spot” would change each time the tuning was adjusted. That’s clearly not the case though, at least with this particular design.
At some point I hope to post a little more video of the radio tuning the band but you’re right John – at least about this particular regen. I do remember having to readjust the regen I had as a teen quite often, but that was a general coverage set which was spanning a wider range of frequencies. For optimum reception, you do need to fine-tune the regeneration on this set when you’ve found a station, but for general band-scanning, you can cover something like half the band without the need to readjust – and even then, not much readjustment is required.
The regeneration is probably a bit more critical for AM stations, as you want to squeeze as much gain out of the receiver as possible before it starts oscillating. If you don’t advance the control enough, the gain drops off dramatically, so the sweet spot is quite critical. With AM stations, if you advance the regen to the critical point, the bandwidth seems to lower to just a few kc/s. The effect is noticeable with the relatively wide bandwidth of AM stations, but although I’ve heard that it’s often possible to limit the bandwidth of regens to just a few hundred hertz by careful adjustment of the regen control, I haven’t been able to do that with this receiver. Serious CW operation would require a good audio filter – unless you have the kind of ears that can pick out one signal among 2 or 3. Sadly, I’m a little green at that kind of operation!
To experience the narrowest possible bandwidth a regen can offer, run the regen just below oscillation, zero-beated to the CW signal of interest. Then turn on a nearby BFO tuned to the signal frequency plus or minus your desired beat note. Stray coupling will provide enough BFO injection into the regenerative detector. The BFO level will need to be controlled to be low enough not to phase-lock the detector; this can be done by e.g. physically adjusting the distance between the BFO and the regen. When properly adjusted, pushing the regen a hair above oscillation should immediately result in a heterodyne whistle with the BFO (i.e. regen oscillator and BFO are not phase locked).
Then, pushing the regen just a hair below oscillation will give few-hundred-hertz selectivity. You will notice a hollow ringing sound on the band noise, and CW signals centered in the passband will also ring (of course you can back down on the regen a bit more to reduce this, widening the bandwidth). Even nicer, you will find that you can peak individual CW signals spaced even just a few hundred hertz apart. Obviously the regen adjustment is critical and will need to be adjusted as you move up/down the band. I tested this at 7 MHz with a JFET Armstrong regen design using a throttle capacitor regeneration control. I measured the opposite sideband attenuation to be about 15 dB in this arrangement. Not bad for a simple regen. More details here:
http://theradioboard.com/rb/viewtopic.php?p=30006#30006
http://groups.yahoo.com/group/regenrx/message/12349
Absolutely fantastic Dave…well done from the UK..m1evc
Congratulations Dave,
You made a beautiful job of it! Thanks for the video.
Cheers,
Mike, AA1TJ
I’ve been looking at the WBR idea for a long time. I think now is the time to build one, thanks to this video! It would make a perfect pair for the Sputnik QRP TX!
The video was very well done and the WBR is really beautiful, a work of art. Perhaps you should consider replacing the cover with a plexiglas one ;-)!