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Old 27th February 2013, 07:46 AM   #1
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Default 1625 tube radio?

I got some RCA 1625 I love to build a tube radio using it. I wanted to check if anybody has any experience? there are some Radio schematics on the web


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Old 27th February 2013, 09:57 AM   #2
DF96 is offline DF96  England
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Google tells me that the 1625 is a version of the 807 output beam tetrode. I know enough about valves and radio not to use one as a radio receiver, except possibly as the audio output stage. Radio transmitter, yes, but for that you need a licence and the knowledge to obtain a licence.
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Old 27th February 2013, 10:29 AM   #3
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This isn't useful except as some kind of a dull art project. As DF96 said, it's a waste of a good tube.

You don't really need experience for something like that. It's no Superheterodyne or PLL, just a simple regenerative receiver consisting of a single tube which does all the work (and it does that badly). Here is everything you need to know: Regenerative circuit - Wikipedia, the free encyclopedia
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Old 27th February 2013, 11:56 AM   #4
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It was used several years as RF and AF power stages in AM transmitters, in 80 to 20 meters hams bands (3500 to 14000 KHz), and a couple of them are capable of modulate a 100W AM emitter in class AB2. There was a common set made by two of them in parallel feeding a PI LC tank, and transformer modulated by other two of them in Class AB2 and a couple of 866 mercury vapor rectifiers. I had one of them several years ago. In ham radio, specially at AM modulation levels, audio quality is not a priority, and the usually shorts duty cycle permits these configuration. Keep in mind, that to modulate a 200W AM transmitter, is needed only a 100W AF output, hiding the performance in RF (Class C)and AF (Class AB) plate efficiency.
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Old 27th February 2013, 12:34 PM   #5
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Real men build something like this: Das Hydradio-Projekt, von Hermann Scharfetter
Even has a mercury vapor heater rectifier !

The GU81 regenerative receiver is nice, too: GU81
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Old 27th February 2013, 12:43 PM   #6
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866's in a variable load as a class AB2 or B are wonderful analog vu-meter :-))
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Old 27th February 2013, 07:25 PM   #7
Cassiel is offline Cassiel  Libya
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Quote:
Originally Posted by the_manta View Post
Real men build something like this: Das Hydradio-Projekt, von Hermann Scharfetter
LOL That doesn't look too masculine. Unless you mean ugly/manly. And no, I don't like the 'arty' radios either. Now that I think about it most vintage radios are nice looking, in those days it was easy to find a beautiful radio - not anymore. Same can be said about tube amps.

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Old 1st March 2013, 07:33 AM   #8
Doz is offline Doz  United Kingdom
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One wonders whether it actually receives anything with all the hash coming from those mercury recs....
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Old 1st March 2013, 08:00 PM   #9
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Been there; done that.

That was my first foray into electronic design: a regen variation that used a 1624, operating at 600Vdc. I was ten y/o at the time, had little idea as to what the hell I was doing, but it worked. I needed to add fixed bias to prevent red plating, as the usual grid leak bias wasn't getting the job done, and so needed to be supplemented with external bias.

It worked, and was basically a "just because I could" project.

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If he's going to the time and expense of making this Rube Goldberg contraption, you'd think he could invest in some proper plate cap connectors, wouldn't you?
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Old 4th March 2013, 11:22 AM   #10
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A regen with 600VDC? Are you crazy? For regen operate properly, use as low plate voltage as you can, there are lots of examples where a 9 to 12V in plate is more than adequate. My project works pretty fine ith 28VDC.
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