Re: RF speech processor

by Andrew Wed Feb 01, 2023 5:33 pm

Glenndk wrote:Hi Andrew

You could camouflage the circuit as a tube - important: Bandpass filter your audio before rf-speech processing:

http://earf.co.uk/rfprocessor.JPG

From:

http://earf.co.uk/weaver.html

Well, camouflaging it would be cheating Very Happy

... but thanks for the idea and the pointers, at any rate the processor is now built... a solid state one Very Happy

by Glenndk Wed Feb 01, 2023 5:23 pm

Hi Andrew

You could camouflage the circuit as a tube - important: Bandpass filter your audio before rf-speech processing:

http://earf.co.uk/rfprocessor.JPG

From:

http://earf.co.uk/weaver.html

by Andrew Wed Jan 11, 2023 5:34 pm

Ivan wrote:Hi Andrew,
a double balanced mixer based on triodes or pentodes is fairly complicated and two mixers are required here. This may be the reason why nobody has designed such circuit.
I am thinking about a device consisting of:
- a ring modulator with 4 vacuum or germanium diodes;
- a triode or pentode (ECO) RF oscillator;
- one stage tube amplifier, perhaps not necessary;
- a neon lamp or two zener diodes as a clipper;
- a crystal filter;
- ring mixer with 4 diodes as a demodulator;
- an output tube AF stage.
It should be reasonable especially if semiconductor diodes were used in both mixers.

Just an idea.

VBR from Ivan OK1SIP

Thank you, Ivan, I think I finally convinced him to go solid state Very Happy

the circuit chosen, at end, was the PA0FRI one

thank you again !

by **Ivan** Fri Jan 06, 2023 8:33 am

Hi Andrew,
a double balanced mixer based on triodes or pentodes is fairly complicated and two mixers are required here. This may be the reason why nobody has designed such circuit.
I am thinking about a device consisting of:
- a ring modulator with 4 vacuum or germanium diodes;
- a triode or pentode (ECO) RF oscillator;
- one stage tube amplifier, perhaps not necessary;
- a neon lamp or two zener diodes as a clipper;
- a crystal filter;
- ring mixer with 4 diodes as a demodulator;
- an output tube AF stage.
It should be reasonable especially if semiconductor diodes were used in both mixers.

Just an idea.

VBR from Ivan OK1SIP

by Andrew Thu Jan 05, 2023 3:35 pm

Hi folks, hope you all will have a nice 2023

Getting to the topic, let me start from this

https://pa0fri.home.xs4all.nl/Diversen/DSBclipper/dsb-clipper.eng.htm

now, the above is a "classic" RF speech processor, where the AF in amplified, converted to RF, clipped (in this case, or limited in other circuits), converted back to AF and then used to fed a TX audio (mic) input

Now, the above circuit is ok, but let's say one owns a boatanchor, say a Collins KWM, and would like to add a TUBE based processor; I searched the intertubes a lot, but it sounds like all those processors are "solid state"; any pointer to a vacuum tube circuit ?

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