[CQ-Contest] CQ-Contest Digest, Vol 247, Issue 21

[Jim Brown]

On 7/23/2023 10:01 AM, dbmcalpine73 at gmail.com wrote:
> Thanks for the comments, Jim.  The problem seems to peak on 20M but can
> occur on higher bands as well.  The strange thing is that it doesn't usually
> occur until I have been operating for five hours or more.  Then, it
> continues tog et worse for a while until I QRT.  

I don't understand the problem. I thought you were experiencing RF noise 
from the hub. What are your symptoms?

I'm trying to isolate the
> inputs to the USB Hub to see if I can tie it down to one or two culprits.
> It seems to manifest itself in higher power output in the K4, e.g., 150-200W
> out which is kinda hard to do with a 1100W rig.  That overdrives the
> KPA-1500 so I have to turn the power on the K4 down to about 5 watts.  I
> have a LPA-100 wattmeter in line with the K4//KPA and it seems to confirm
> that the power is higher than it should be.

I run 100W contests like I think you're describing -- 2-3 W from the K4 
to the KPA1500, with an LP100A in line with two probes, one in the 
output of the K4, the other on the output of the 87A. In digital modes, 
I set audio drive to the K4 for ALC indication of 5. I operate this way 
because the radios on my operating desk run from a 100Ah LiFePO4 battery 
that is float-charged from a re-purposed PSU for a vintage Thinkpad; it 
can keep up with SO2R at the levels needed to drive amps, but not at 100W.

73, Jim K9YC