Russian rod pentode circuits

[Murphyv310]

   
Here you go.
I'll add a description over the next couple of days.

[Murphyv310]

Hi.
The circuit doesn't seem to require any adjustment to the feedback, going too low on HT volts and it just stops, go above 110 v and the audio gets very distorted.
Hand capacitance is a big problem so I use a plastic knitting needle to keep me away when tuning. You can add a loosely coupled single turn coil adjacent to L2 at one end to improve reception with it connected to a dipole. Station Separation is not an issue and it pulls in very weak FM stations with ease.
Two disadvantages are, 1.... I'd not say by any means this is hi fi, it is a little distorted on reasonable signals and worse with strong ones. 2..... These super Regen receivers radiate and for a fair distance, Ideally you need an RF stage for isolation.
It may work better in a tobacco tin for screening and reducing hand capacitance.
HT current is between 0.95 and 1.1ma dependent on HT volts.
Have fun.

[Murphyv310]

Hi.
I've tried this in a small tin and found it works very well, I glued a hollow plastic tube to the beehive trimmer and aligned this through a small hole in the tin. The headphone lead was passed through a grommet and a lead from a one turn coil was wound with half a dozen turns round the headphone lead as a loosely coupled cap to use the headphone cable as an aerial. Results are brilliant, I can pull in all the FM stations a decent radio can.
My next thing is to do away with all those PP3 batteries and the 2v cyclon. The little inverter I've used on the pantry TX works perfectly in this radio and from 2 AA NI-MH cells plus they drive the filaments too, the whole thing fits in a coat pocket and is very stable indeed.

[radioman]

Brilliant stuff Trev. - I look forward to seeing and listening to this when I next visit !

Andy

[BusyBee]

That's excellent Trevor. An interesting little circuit. I like simple - I always seem to overdo it with bits and pieces lol. Are you going to produce one of your videos?

Tracy

[Murphyv310]

Hi.
Yes I'll be doing a video in the next few days or early next week . I'm undergoing some tests at the moment at hospital so playing in the shed could be curtailed a bit.

[Murphyv310]

Hi.
I did get some time this afternoon and pulled it all out of the Tin box. I have refitted the original trimmer so I can do a couple of videos. What I will need to do though is to feed the output into an amp as even using an output transformer and speaker it isn't really loud enough for the camera mic to respond. I can hear the speaker audio in a silent room but ears are better than a phone!!!
The little inverter tends to cause a bit of whistling on the audio so I'll be trying to filter it better, the inverter runs between 7-10Khz dependent on load. Battery current for both HT & LT is around 120ma from two NI-MH AA cells, a bit more than I was expecting. Also remember this circuit is demodulating by slope detection.

[BusyBee]

I had forgotton you were using headphones, when thinking about video. It really does go to show though, how wonderful our ears are.

Tracy

[Murphyv310]

Hi Tracy.
I'm determined to do a video of this. So I'm building a second stage using another 1Ж29Б valve as an audio amp and output, for a speaker. So the small tin is a no no. Also the little inverter may struggle. I hope to finish this addition by the weekend and do the video.
I've a suitable larger tin that will house 10 PP3 batteries and two AA cells.

[BusyBee]

I'll look forward to looking Trevor. An audio amp with speaker output is something that I plan to look into. At the moment I have an old module made from a kit (years ago - Germanium transistors) with a little Tandy speaker unit which I use on the bench for tests. A valve unit would be more the part, but the transistor kit is nicely vintage (except perhaps for how I have boxed the amp).

Tracy