Having an issue with my KPA500 and a non-elecraft radio. I’ve got an Icom 
IC-705 connected to my KPA500 and KAT500. By dropping the 705’s output power to 
4 watts and pressing Tune on the KAT500 with the amp in OPER mode, I’m able to 
get the tuner to give me a good match on just about all bands to my Zerofive 
Flagpole Vertical. Then, turning the power level up to max (10 watts) on the 
IC-705, the amp gives me anywhere from 210 to 250 watts output, depending on 
the band. And that’s fine for me right now.

However, what I’m seeing is that when the amp is in OPER mode, my receive 
signal strength drops way, way off to the point I have to go full AF volume to 
hear signals. If I put the amp in STBY, signal levels go back to normal. I also 
notice that the amp fan doesn’t take too long to crank up to high speed, and 
the PA temp is sitting around 67 C. 

I also have a K3. When I power up the K3 and switch the antenna over to the K3 
on the same band as the IC-705 - there is no drop in signal level on it when 
switching between OPER and STBY on the amp. And, yes, when I’m using the 
IC-705, I press the corresponding BAND button on the amp.

OK - some further info: if I have the K3 sitting on the same band as the IC-705 
this does not happen - going from STBY to OPER on the amp makes no difference 
on receive level on the IC-705. But if I power off the K3, the IC-705 reverts 
to its partially-deaf state.

Somewhere long ago in a far distant galaxy, I recall Jack W6FB mentioning that 
the K3 pulls some signal to zero when it is powered off. I suspect that may be 
what is happening here but for the life of me I can’t recall the exact 
conversation. I’d like to get to the point where I can run the IC-705 with this 
tuner and amp without having the K3 in the equation, as the K3 will be going on 
the sale block in the near future, in anticipation of a K4D delivery. 

Any ideas?  Jack - are you listening? :-)

Jim / K7TXA

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