[Elecraft] Help with K3 & THP amp

[Jim Brown]

On Mon,12/7/2015 7:51 AM, dlrwild1 at verizon.net wrote:
> Previously I used this same set-up with my IC-756PRO2. The THP amp has a variable pot on the rear panel to adjust and set ALC voltage or relay voltage? for various radios. I don’t think that I need to readjust this with the K3, but not sure. I don’t want to damage the relays in either the K3 or THP amp.

I don't know this amplifier, but in general, it is VERY bad practice to 
use AGC from the amp to set drive power from a rig. Doing so usually 
results in bad splatter and key clicks. As long ago as the early 1980s, 
mfrs of decent power amps (in this case, Ten Tec) were telling customers 
(in the user manual) to NOT use AGC to set drive power.

The K3 is very well behaved as an exciter for power amps, so the right 
way to set drive power is to use the Power Out knob on the K3. I've 
never done it any other way, including with a TS850, FT1000MP, and a 
K2/100.

The ONLY good use of AGC between a power amp and a rig is to protect the 
amp if something in the antenna circuit fails. To do that, hook up the 
AGC and carefully set it so that it does not reduce drive power in 
normal operation at the highest power at which you operate.

FWIW -- I have NEVER used AGC between an amp and a rig. My amps are a 
KPA500 and Ten Tec 425s (legal limit tubes, a pair of 3CX800A7s).

73, Jim K9YC