TheRadioBoard

Has anyone built a superhet using a triode autodyne circuit? Since the term "Autodyne" has been used for a number of totally different applications, I should clarify that I'm referring to a single tube (triode in this case) self-oscillating mixer for a superhet.

I think the first popular one was the Pressley circuit, and then some others came along with various improvements. For example, the Van B. Roberts circuit allowed the use of a ganged tuning capacitor because the rotors of the RF and LO caps were both at ground potential. Most of these circuits used some type of signal canceling arrangement at the antenna input to minimize radiation of the local oscillator signal.

I've had a hankering to build one of these, and it might be my project for the summer homebrew contest. But, I'd like to hear opinions on the various versions of the circuits.

Well, close.
http://www.sparkbench.com/ll/ll.html

I made a a fake 'dubbleroosterlamp" with a 5672 and got this old LL set going. Ok, not a triode.

tried copying the same circuit using a 22 on a breadboard and could not get it to fly.

I'd really like to make a good-looking OLD tube (like a 22) work as a 1AD in spite of the limitations. I'd be interested to hear your results.

Hi Bob

Have you seen the Round Autodyne?

Have no further info than that unfortunately, and no detailed expalnation etc..

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regards,

George ..
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I thought I had amnesia, I just forgot I didn't.

Thanks guys.

Bill,
I think I've looked at that receiver before, but with all the tubes in it, I hadn't noticed that it was an autodyne mixer. Interesting circuit. It looks like both grids on V1 are control grids. Which tube did you use for a sub, and how did you wire it?

George,
Thanks for the interesting information. I followed up by doing a search for patents by H. J. Round, and came up with probably a hundred or so, but couldn't find the autodyne circuit. I didn't look through them all, only the ones with promising titles. I'll have to spend a bit more time looking through them. It's also possible that some of his inventions were only patented in Britain, and I don't think the site I was searching included British patents.

My plans at this point are for a 3 triode receiver. the first stage would be an autodyne mixer. The second stage would be a regenerative detector. The third stage would be audio (and possibly a reflexed RF amp). I plan to use modern tubes, since I don't have a good supply of old ones. If it works well, then I might attempt building an old tube version of it later.

Hey Bob,
How about using a triple triode compactron tube?

Dave

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Please visit my website at: http://www.makearadio.com

Umm, the idea had crossed my mind.

Hi ex:
Liked the LL section on your site. Had not seen that one before. As you said, hang on to those Phillips tubes. They are even scarse as duds (fillers).

By the way, I'm sure that many of you have seen this, but for those who haven't. The "Radio News Superheterodyne book" can be downloaded from this great site:
http://www.tuberadio.it/docs.htm

The book has a number of superhet construction articles from the early 1920's including the Pressley autodyne circuit.

Meanwhile, I'm thinking that if I have a reflexed RF stage, then I don't need to worry too much about local oscillator radiation. So, that may simply the choice of mixer circuit. I've been thinking of the mixer circuit used in the Philco 80 and 84. I could probably sub a triode instead of the pentode used in that circuit.

Bob,

I'm all ears on this one. A three triode compactron superhet would make a unique, compact set. It will be fun to follow this project. Keep us posted.

Looks like an "arms race" has begun. Hmmm, may have to consider finishing my double twin triode set that I started a while back!

"Rob"

The autodyne converter I've had considerable success with consisted of an antenna tuned circuit coupled through a small capacitor into the grid of a cathode feedback oscillator. While radiation of the oscillator is inescapable with such an arrangement, I never encountered any issues with tuning interaction or signal overload on the BCB. For an HF application, such a circuit would be unsuitable. If you're willing to use more that one triode then a cathode injected mixer offers decent performance while a double triode Pullen mixer meets or exceeds the strong signal and low noise performance of beam deflection tubes.

73's

This may be a little OT, but it's about triode superhets. A while back, while surfing through cyberspace looking for info on the Western Electric 215-A "peanut" tube, I ran across a page devoted to a 1926 vintage super that used ten of the little rascals:

http://www.theoldradiofixerupperguy.com/su10.html

The thing that most impressed me in the article was the exceptionally long filament life claimed for these little tubes. It appears they can still be found, and although kind of pricey, they're still a lot less expensive than a WD-11, and apparently are a lot more robust. One downside is that sockets are harder to find than the tubes themselves, but a dedicated DIYer might be able to make something that would work.

I think I can see a couple of peanut tubes in my collection sometime in the future, and they will be used in a project of some sort.

What are you using to view the files? Thay are all in some strange format I've never seen before.

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Secret of Electronics - keep the smoke _in_ the wires.

AUTODYNE

Although a receiver can be called many things, and I dont wish to argue with what exactly constitutes an "autodyne receiver".

The modern general cosensus of what an autodyne is, seems to be:

A receiver who's detector generates its own oscillations(Local Carrier) in order to demodulate a radio signal all the way down to an Audio Baseband.

If you accept this definition there are 2 receiver types that fall into the category of "autodyne detector" receivers. The regen(when oscillating), and the Direct Conversion receiver.

This is apparently the most modern and well accepted definition, but hey its all a matter of terminologoy.

73,s kb0lxy

edited for clarity

microbes, djvu is a "portable" documant format, about like PDF. look here for more.
http://djvu.org/

i use Linux and in Debian they just pop up if i double clock them in the filemanager.

Oh boy, I've been out of town for a few days, and the responses have been piling up.



Not sure about an arms race, but since I was trying to keep to one active device for the winter AD contest, the summer contest will be a nice opportunity to spread the wings a bit and fatten up the parts count.



I'd like to build a Pullen mixer on some future radio project, but with a three tube limit, your first suggestion sounds like a better fit this time round. I'm getting less concerned about radiation all the time.



I agree. The meaning of "autodyne" has evolved over time. During the early days of superhets, it was used to mean a one tube oscillator/mixer, and then over the years, I've seen it used for various regen circuits, etc.



Now I have to get busy and start pulling a bunch of parts together, and start building something.