[Elecraft] KPA1500 in the IARU Contest Last Weekend

[Ray Spreadbury]

Hi

I was a member of the UK HQ team for this 24hour IARU event last weekend and
was one of the two Ops on 40M SSB. 

We took it in turns to be the Run station every 4 hours and I was using a
40M 2-El yagi at 60ft. I noticed that every 30-60mins, I needed to do a
re-tune on the KPA1500 to keep the SWR at or near to 1.1:1, as it seemed to
gradually creep up over time. The amp temp peaked at 70C but was mostly at
about 55C. The SWR never got above 1.5:1 using KPA1500 screen but I know
that the yagi was really presenting about 1.6:1 at the run frequency. When
not operating as the Run station the other Op was in Partner mode spotting
mults & helping with call identification.

We were using the WinTest logging program as this enables us to private
network with the other UK HQ stations (one on CW & one on SSB for each
contest band ie. a total 12 stations at any one time, plus Partners).
Because of Covid, this year we were all single Ops working from home rather
than just a few multi op stations.

My K3S & the KPA1500 worked faultlessly for the 24hours as did Wintest but I
wonder what was the cause of the SWR increasing over time & needing a
re-tune?

73 Ray G3XLG