[ARC5] Q about modulation transformer.

[J Mcvey]

The original SCR274/ATA setup was different than the ARC 5. SCR274 are screen modulated, while the ARC5 units were plate modulated.A simple solution for the screen modulation is to put an audio output transformer secondary winding in series with the grid circuit. Drive the 8 ohm secondary of the transformer with a garden variety pa amp.
 


     On Thursday, October 8, 2015 7:28 PM, Kenneth G. Gordon <kgordon2006 at frontier.com> wrote:
   

 On 9 Oct 2015 at 9:06, Leslie Smith wrote:

> I'm writing about eBay item #351537579927.
> 
> You can see photos of this item - attached.
> It is listed as part of ART-13.  I presume this is a Collins
> Transmitter.  We rarely see such an item, here in Australia, although
> one fellow in Sydney has one.

That is the audio pre-amp and sidetone oscillator. Its primary input is the 
microphone.

The modulator in the ART-13 is driven by that module, and consists of a pair 
of 811s.

> I'm looking for a modulator I can "mate" with an ATA or ARC T-19
> transmitter.

Well, the output level of that pre-amp is only couple of watts, as far as I 
know, so unless you wanted to use screen or grid modulation, it probably 
won't do.

I CAN suggest that you try controlled-carrier screen modulation with your 
transmitters. The audio power required is very low, and it "almost" sounds 
like SSB to an SSB person.

For my horribly hacked transmitters, I intend to use controlled-carrier 
modulation.

Ken W7EKB
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