Stew Perry Topband Challenge
Call: K1LT
Operator(s): K1LT
Station: K1LT
Class: Single Op HP
QTH: EM89ps
Operating Time (hrs):
Summary:
Total: QSOs = 101 Total Score = 238
Club: Mad River Radio Club
Comments:
Jeff, K8ND, loaned me his NCC-2 antenna phasing box. I planned to see
if the NCC-2 could out-perform the circuit hack that I previously used
to tune a 2-element end-fire array to null out my transmitted signal.
Wednesday before the contest I set up the NCC-2 and observed that it
could achieve a deep null, although the tuning was a bit touchy.
Thursday I intended to check to see if the NCC-2 could provide this
null while transmitting 1500 watts. However, when I turned on the
receiver, the bandscope was wall-to-wall with power-line impulse
noise.
I think I have seen this noise before intermittently. It appears when
the temperature goes below about 15-20 degrees Fahrenheit, and hangs
around until the temperature goes over 35 or thereabouts. The noise
is sporadic, and the duty cycle increases as the temperature
decreases. Thursday, the temperature was in the single digits.
The weather forecast called for the temperature to remain quite low
through the contest period, so I was officially worried. Friday it
warmed up to the mid 20s and the noise became somewhat sparse and
sporadic and it seemed like the Beverages were impacted less than the
phased arrays. However, Saturday morning the temperature was again
low and the noise was mostly full-time and much stronger.
I gathered my noise tracking gear and made about 3 attempts to locate
the noise. On Friday, a trip around the 'block' in the car showed the
noise to be loudest on 1700 kHz when on my street, just east of the
house. With the large loop and the KX3, walking east showed the noise
peaking in the direction of the electric pole in front of the east
neighbor's house when I was west of the pole on the east-west road.
But when east of the pole, the loop nulled best when pointed directly
at the power line. When I was east of the next pole, then the loop
pointed back towards the first pole. Though not definitive, the
implication was that the noise came from that single electric pole.
Saturday I repeated the process with the MFJ-852 'noise receiver'.
This time there appeared to be 2 noise sources, one coming from
possibly that same electric pole and another coming from somewhere
else. I walked a longer stretch of the road in front of my house and
saw no other intensity peaks. Meanwhile, the noise seemed to affect
reception on all receiving antennas by raising the noise floor about
25 db.
Around 2200Z, I started operating in S&P mode to see how many contacts
I could make and to see how badly the noise affected operating. I
worked TM6M and OK7K and several east coast stations. I took several
breaks because the noise was very frustrating. I had the noise
blankers enabled on all of the receivers, but as signals got stronger
and more numerous, the noise blankers became less and less effective.
By about 0000Z, the blankers were decreasing the noise level by only a
few db. Any strong signal splattered across the entire band.
Suddenly, the transmit SWR went to infinity. Not just super-high, but
99.9:1 on the K3 meter. The amplifier wasn't happy, either. So,
after 2 non-stop 20 db noise sources and a failed transmitting
antenna, I decided to quit.
After a while I figured I might try walking out to the splice in the
transmit feedline and see if a jiggle would restore operation.
However, previous splice disruptions did not cause an 'infinite' SWR
(just very high) and the last 'jiggle' was actually a 're-tightening'
of the connector. Nevertheless, I took a walk in the fresh 3 inches
of snow under the almost full moon in 10-degree air. I roamed around
in the woods where the feedline was suppose to be, but I could not
find it. When I got back to the house, it occurred to me that I could
use the VNA to 'TDR' the feedline to see if the break was at the
splice. The TDR said that the break was a complete open circuit about
25 feet from the shack, which means it must be where coax transitions
to hardline under the deck.
I tuned up the 80 meter vertical for 160 with the antenna tuner. The
match was not quite perfect (about 2.5:1) and the tuning was a bit
critical, which means high Q which means loss and potential
overheating or arcing. Nevertheless with the amplifier at about 500
watts, I was able to make another 25 QSOs to get my total over 100,
including PJ7/UT6UD after numerous calls.
I took another break. Then I went outside and shoveled the snow off
the deck and peered underneath at the coax to hardline junction.
Everything looked the same as always. I got a stick and tried rapping
the connector, but it was hard to impart much impulse in the
constrained space. So I wedged the stick between the connector and
some other stuff to see if a little strain might make a difference.
But there was no change.
I took another break. Then I went outside to start taking out deck
screws to lift a few boards to gain access to the connector in
question, but my knees got cold. Also it was hard to find all of the
screws in the dark. I abandonded that idea.
I took another break. Now I am typing this report. This is the first
time ever I have abandoned a 160 meter contest effort from this
location, and it feels terrible. Hopefully the noise will hang around
long enough to track it down for certain. I'll probably have to haul
a laptop and the VNC to the basement to get a better fix on the
location of the feedline fault. Once I discover the failure, then I
can learn the appropriate lesson about reliable engineering.
Conditions sounded decent the best I could tell through the noise.
Besides working the 2 Europeans, I could hear some of OK7K's Eu
callers. By 0130Z, the west coast was coming through and the noise
was reduced on the phased array pointed west. Oh well.
Hopefully back to a fully operational battle station by CQ WW 160.
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