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

[Phil & Debbie Salas]

"I don't know if others have experienced this issue, but from previous
postings on low power on 10m it's possible...

My K3/100 has the KAT3 auto ATU fitted, when I have the ATU in bypass
and use the antenna 1 socket (as you are asked to when setting up the
K3's power calibration), there is a residual SWR when on the 10m band.
If I select antenna socket 2 there is no residual SWR. I've seen as high
as a 1.7:1 SWR, which not surprisingly results in lower power on 10m
unless I use the internal ATU.  Anyone else seen this?  73 Dave, G4AON
K3/100 #80"

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