Author Topic: EL504 as a "QRP" RF amp  (Read 441 times)

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Online A.Z.

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EL504 as a "QRP" RF amp
« on: June 12, 2021, 03:29:52 pm »
Hello folks, a friend has quite a bunch of EL504 (Ok PL504) recovered mainly from old TV sets, now he asked me if it may be possible to use some of those tubes (say 2 or 4) to put together an RF amplifier which, driven by a 5W QRP transmitter, could offer some "QRO" output; seeking on the intertubes, I found this schematic

http://www.cqham.ru/projects/25w_qro.pdf

but my friend told me that, while he likes it, he would like a two or more tubes amp, so here I am asking for pointers
 

Online TimFox

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Re: EL504 as a "QRP" RF amp
« Reply #1 on: June 12, 2021, 03:34:13 pm »
I’m concerned about the mains feed to the HV supply:  is there a transformer not on the schematic page?
A 240V to 240V toroidal isolation transformer would be a good idea.
 

Online A.Z.

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Re: EL504 as a "QRP" RF amp
« Reply #2 on: June 12, 2021, 03:50:01 pm »
Hi Tim

Yes, noticed it, but aside from that schematic, which apparently is the only one around (didn't find much for 504 tubes as RF amps), what I'm asking is if there are other schematics using two or more tubes; to say it all, I suggested going for PL519 or even 813 tubes in grounded grid, but my friend insists about trying to use the 504...
 


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