[Elecraft] K3 low power on 10m - was Wattmeter Calibration

[Dave G4AON]

Phil

Several replies to the "Wattmeter Calibration" thread mentioned lower 
power levels on 10m only, which was what I saw. The SWR was as high as 
1.7:1, but mysteriously dropped to around 1.3:1 after trying the ATU and 
going back to bypass. Maybe in my case it's more a case of an odd length 
of coax, or some component that gives an odd impedance on 10m as seen by 
the SWR circuitry? Why it should drop after trying the ATU - and stay 
there is very odd...

Dave, G4AON
=============

Dave - I had this same problem. But it occurred only after I'd been using
the radio for a little while. I was operating on 20M CW into a high SWR
(7:1) using the tuner, when suddenly the tuned SWR popped up. I retuned,
and everything seemed fine. After that though, I found that the residual
SWR was around 1.2:1 on 17 meters, and about 2:1 or 3:1 on 15-, 12-, and 10
meters. I also had several more occurances of the tuned SWR suddenly
changing, resulting in having to retune when operating on other bands.
Elecraft sent me a new tuner and that fixed the problem. I wondered if
maybe an output transient suppressor failed under a high voltage condition
due to the high SWR. Shouldn't happen, but maybe a bad batch of transient
suppressors got put into the tuners? Or maybe a set of relay contacts
shorted or stayed open. This is just a guess on my part,. All the relays
were operating correctly (I stepped through them manually). It wass very
funny that the residual SWR problem was only on those few bands (even
6-meters was OK). I had the problem on both A & B antenna ports, which
tends to support the idea of a bad realy, as both transient suppressors
would have had to be bad to affect both ports - but I guess this could
happen. However, since you are having this on one port only, you might look
at that one transient suppressor on that port - maybe cut it out of the
circuit and see if the problem goes away.

Phil - AD5X