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Old 28th August 2009, 09:11 AM   #1
Arnulf is offline Arnulf  Europe
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Default OT: vacuum diode AM detector schematics ?

I've been googling for practical (= complete with component values) AM detector schematics employing vacuum diode for the last two days with no success. There is plenty of theory to be found, many sketches but no components values anywhere.

While this isn't related to amplifiers directly I'm sure there are many of you who know of such schematics online and can hopefully point me in the right direction.

Thanks!
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Old 28th August 2009, 01:18 PM   #2
Arnulf is offline Arnulf  Europe
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To answer my own question: this is the only schematic that I've found on the subject. There surely are more out there ?
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Old 28th August 2009, 01:39 PM   #3
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I think you will find what you are looking for (and more) in the Radiotron designer's Handbook. Both the 1940's edition (350 pages) and the 1950's edition (1500 pages!) are online at http://www.pmillett.com/technical_books_online.htm

While you're there, you might also look at the book "Radio Reciever Design".

Last edited by Tom Bavis; 28th August 2009 at 01:52 PM.
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Old 28th August 2009, 01:46 PM   #4
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Couldn't see any schematic in your last post.

I suspect you will find nothing about this topic on the internet, it stopped being an area of interest long before the internet ever happened, so why would anyone go to the bother of scanning old books, schematics etc and posting them?

I did quite a lot of R&D on this topic back in the late 60's, early 70's and got most of my ideas from the Radiotron Designers Handbook. The infinite impedance detector proved to be the best. Also suggest you take a look at the schematics for the Quad AM tube tuners, AM2 & AM3. That will give you a good working example of a diode detector - but the infinite impedance one sounds far better.

Regards, Allen (Vacuum State)
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Old 28th August 2009, 04:37 PM   #5
rtsang is offline rtsang  Hong Kong
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Default Do you mean detector after the IF stage of a superheterodyne radio?

Here is a web page with full schematics and explanation for the All American Five radios.

All American Five - Detector Section

I also have a schematics of several German AM/FM tube radios that I owned.
I can post it if you are interested.

Raymond.
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Old 28th August 2009, 05:49 PM   #6
kevinkr is offline kevinkr  United States
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Not sure what your specific interest in tube diode based am detectors might be, but if you are planning to build an actual radio you might want to consider a triode based regenerative receiver instead.

http://www.lindsaybks.com/bks/twin/index.html Check out the Doerle Twinplex as an example of a radio that people are still building today.

There is quite a lot of stuff available online if you google for it, and Lindsay Books has republished a lot of the Gernsback radio series from the early 1930s and there is quite a crowd building these things. (Myself included)

Doerle Twinplex: http://dzabcik.home.texas.net/doerle.html
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Old 28th August 2009, 06:27 PM   #7
Arnulf is offline Arnulf  Europe
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Thanks for replies guys !

I already checked RDH (chapter 27). There is plenty of theory there but no practical circuits, alas I will look into this "infinite impedance detector" (which BTW sounds like something that uses an active, high-impedance input device, therefore not the thing I'm really after).

There are plenty designs using active device(s) (triode/pentode) described online. I'm not after these. I have a simple pentode-based regenerative receiver breadboarded, waiting for (ferrite) antenna + coil.

What I'm after are functional schematic od vacuum diode detectors. Why am I interested in these ? While I was bored and had nothing better to do over the course of the last weekend I came across serveral websites which outlined the history of vacuum tubes and/or electronics and they all mentioned (Flemming's) vacuum diode as the thing that started it all, alegedly allowing big advances in radio technology (this was in the days when crystal detectors were practical means of receiving AM with relatively low forward voltage drop). The only practical use for device with Vf of 100+V I see (mains rectifier/battery charger) has nothing to do with miniscule signals that aerial picks up so I'd like to see a couple of practical examples of vacuum diode AM detectors I was under the impression that DeForrest's tiode (Audion) was by far more influential so these schematics ought to prove me wrong.

The link I posted above has a simplified schematic right on top with components described in the text below. It shows up correctly for me but I want more schematics in order to be able to compare them.

That's all
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Old 28th August 2009, 07:12 PM   #8
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I am sure you will like it:


http://www.noding.com/la8ak/24a.htm

12P2000 pentode used as very sneaky detector.

Click the image to open in full size.

Speaking of what started it all, it was a Silicon Carbide diode actually. That means, going for the earliest radio technology, you have to use the latest semiconductor one.

Last edited by Wavebourn; 28th August 2009 at 07:16 PM.
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Old 28th August 2009, 10:15 PM   #9
6f6 is offline 6f6  United States
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Go to www.antiqueradios.com and look under the Archive section; there you will be able to download the whole Elements of Radio Servicing Book and learn all about detectors as well as superheterodyne radio theory.
If you want to look at random schematics, go to www.nostalgiaair.org; there you will find schematics for nearly every radio from the 20s, 30s, and 40s. I would look at random radios from Philco, RCA Victor, Zenith, General Electric, and Silvertone (Sears&Roebuck) if I wanted to see the most common practices.
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Old 28th August 2009, 11:43 PM   #10
kevinkr is offline kevinkr  United States
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A very good vacuum tube diode for AM or FM detectors would be the 6AL5/12AL5.. Equivalents 5726 and EAA91.

They are quite useful detectors and may be used as low voltage bias rectifiers in amplifiers if you must have all tubes.

Quote:
Originally Posted by Arnulf View Post
Thanks for replies guys !

I already checked RDH (chapter 27). There is plenty of theory there but no practical circuits, alas I will look into this "infinite impedance detector" (which BTW sounds like something that uses an active, high-impedance input device, therefore not the thing I'm really after).

There are plenty designs using active device(s) (triode/pentode) described online. I'm not after these. I have a simple pentode-based regenerative receiver breadboarded, waiting for (ferrite) antenna + coil.

What I'm after are functional schematic od vacuum diode detectors. Why am I interested in these ? While I was bored and had nothing better to do over the course of the last weekend I came across serveral websites which outlined the history of vacuum tubes and/or electronics and they all mentioned (Flemming's) vacuum diode as the thing that started it all, alegedly allowing big advances in radio technology (this was in the days when crystal detectors were practical means of receiving AM with relatively low forward voltage drop). The only practical use for device with Vf of 100+V I see (mains rectifier/battery charger) has nothing to do with miniscule signals that aerial picks up so I'd like to see a couple of practical examples of vacuum diode AM detectors I was under the impression that DeForrest's tiode (Audion) was by far more influential so these schematics ought to prove me wrong.

The link I posted above has a simplified schematic right on top with components described in the text below. It shows up correctly for me but I want more schematics in order to be able to compare them.

That's all
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