[ARC5] Modulation for ARC-5 transmitters.

[Dennis DuVall]

The circuits in the references are cathode modulators. Both articles present the same circuit which works quite well but provides 
only a limited amount of incidental “carrier control” action.  Also, make sure only the cathode of the output amplifier tube(s) is 
connected to the “key” jack before you try to use these circuits.  

There are several schemes to achieve true carrier control, see many of the older editions of the ARRL handbook, CQ magazine
articles, etc..
.
Dennis D.  W7QHO
Glendale, CA

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> On Oct 8, 2015, at 4:56 PM, Kenneth G. Gordon <kgordon2006 at frontier.com> wrote:
> 
> Leslie:
> 
> There was an article some time ago in Electric Radio Magazine on 
> controlled-carrier AM modulation which I found to be a very well-done article, 
> and it explained a lot.
> 
> There was also a recent article in ER on the same subject, but I was very 
> "under-whelmed" by that article. I found it very difficult to follow.
> 
> My first transmitter, a Heathkit DX-35 used CC modulation, and I have 
> always liked that mode ever since.
> 
> You might also consider this modulator:
> 
> http://www.w7ekb.com/glowbugs/projects/SimplestModulator.pdf
> 
> Which plugs into the key-jack of any cathode-keyed transmitter. I tried one of 
> these once and was very pleasantly surprised at how well it worked and how 
> good it sounded.
> 
> Here is another article on that same modulator with different info:
> 
> http://www.w7ekb.com/glowbugs/projects/SimpleGridModulator.pdf
> 
> Using CC modulation, you should be able to achieve output equal to the full 
> plate dissipation capability of your final amp tubes, which in the case of a 
> pair of 1625s, should be close to 60 watts. (807/1625 has 30 watts PD rating 
> in ICAS)
> 
> Also, CC modulation works extremely well when fed into a modern linear 
> amplifier, unlike straight plate modulation, which must be "dialed back" 
> severely to prevent the following linear from being overloaded.
> 
> Ken W7EKB
> ______________________________________________________________