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 Post subject: Modulation: Need informations about double control pentodes
PostPosted: Oct Sun 27, 2019 2:20 pm 
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Joined: May Tue 14, 2013 7:23 am
Posts: 8
Location: Germany, Region M-V (near Rostock)
Hello, radiofriends,

I am developing a transmitter to supply old radios with Musik, only in my house and garden, and tests.

Guideline for me is always the use of very old parts and historic circuits, the tubes and components are mostly old, but unused stock items ("NOS" = New Old stock).
The tubes are mostly old radio tubes, Telefunken, Philips.

In my project, I only want to use stages in A-Class operation, even if that is not economical, just because probably no one has built something like that, I want to realize it.

I realized a modulator circuit from Joe Sousa, a circuit with a dual-control pentode.

The circuit and explanation is here.

I am developing a transmitter to supply old radios.

Guideline for me is always the use of very old parts and historic circuits, the tubes and components are mostly old, but unused stock items ("NOS" = New Old stock).
The tubes are mostly old radio tubes, Telefunken, Philips.

In my project, I only want to use stages in A-Class operation, even if that is not economical, just because probably no one has built something like that, I want to realize it.

I realized a modulator circuit from Joe Sousa, a circuit with a dual-control pentode.

The circuit and explanation is here.

https://www.radiomuseum.org/forum/hi_fi_am_transmitter.html

The circuit works well, but it had to be adapted to the very old tube, these had not been developed for double control.

I am currently developing the following amplifier stages.
I would like to achieve an output power of 2 watts.

I have questions about this:
Does anyone know if this modulation circuit - for normal AM modulation! - was used somewhere?

The circuit works well, but it had to be adapted to the very old tube, these had not been developed for double control.

I am currently developing the following amplifier stages.
I would like to achieve an output power of 2 watts.

I have questions about this:
Does anyone know if this modulation circuit - for normal AM modulation! - was used somewhere?

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 Post subject: Re: Modulation: Need informations about double control pento
PostPosted: Oct Mon 28, 2019 10:09 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 14110
The big pin type 837 can be suppressor modulated, no idea if they are available on your side of the pond.

http://www.nj7p.org/Tubes/SQL/Tube_query.php?Type=837

Dual control types like 6888, 6GY6, 6DT6 etc can be used for a home broadcaster and require less than 200v B+(err EHT_). With a tuned antenna range of 100ft is common.

I built this 9KC6 transmitter just because I could and it is likely only one on planet. A similar circuit can be used to modulate G3 on many std pentodes but amount of negative voltage will vary widely.


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