ARRL 160-Meter Contest
Call: K7QA
Operator(s): K7QA
Station: K7QA
Class: SO Unlimited HP
QTH: MT
Operating Time (hrs): 18
Summary:
Total: QSOs = 671 Sections = 77 Countries = 12 Total Score = 115,752
Club: Big Sky Contesters
Comments:
Several Murphy-induced equipment SNAFUS struck that wasted significant operating
time here. Had not yet ran a recently acquired used IC-7300 on 160 for contests
yet. I use 2 different switchable rx antennas, a 3ele HiZ array and a fw 160
H-loop, both over 200 feet from the shunt fed 63 ft tx tower. Early Friday
evening I noticed my amp output power was dropping with VSWR increasing
randomly. First thought was something went haywire with the T matching net or
the slant wire feed. Redid all the connections and checked cap values but
nothing bad found there. Then I noticed the output changes were tracking with
switching the HiZ rx directions. And the H-loop was unusable for rx while
transmitting. Uh oh...RF from the tx antenna getting into the rx antennas and
recirculating thru the IC-7300 into the amp. I never had this problem with the
old K2/100.
Apparently the IC-7300 front end is very sensitive at the separate rx antenna
input spigot modification. Or the isolation is a lot worse than in the stock
separate rx antenna input of the K2/100. I had no inline attenuators handy, so I
trudged thru the cold and snow to remove the preamps at the rx antennas. That
solved the problem. The IC-7300 input sensitivity and AGC is good enough to
compensate to hear weak sigs well.
If recirculating RF thru the exciter didn't cause enough problems, the other
self-inflicted gotcha made the mess worse. While trying to compensate for the
decreasing output power and VSWR jumping around, I cranked up the IC-7300 drive
to the amp a bit too far causing the PA tube to go spurious. Dick, K4XU tracked
me down and let me know about the mischief. The 3CX-1500 output tube shorted
right after I got the used amp and was replaced with a used softy that has been
getting softer ever since. Looking at a spectrum analyzer today, I can only hit
the amp with 20 watts max before the spurs start to form on most bands at less
than 500w out. Time for Santa to bring a new tube. ($1800 list new).
Getting back to the contest, we were hoping the excellent polar EU path would be
open like it was for CQWW. But we only heard and worked a few Russians and JAs
in this one. Seems like everywhere else in the US was hearing and working EU. MT
is truly an RF black hole. Otherwise we worked just about everything heard or
called. The band was fished out by 1300Z Sunday from here.
QA
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