This was another fun event for those of us that like to listen to a lot of
band hiss in between our CQ's. .
Conditions seemed better at the 7 PM start then they did when I stopped at
10PM in fairly hard rain.
Band Mode QSOs Grd
420 CW 7 4
420 USB 7 4
Total Both 14 8
This is a new grid total high for me on this band, even though 3 adjacent
grids were not contacted.
As I've reflected before, being focused on just one band offers a good
chance to test drive your latest station changes to try and determine if
they are really improvements. My venture into 70 cm is in its infancy so
there are plenty of things I've needed to work on, and still do. The last
event "seriously" trying 70 cm was the January ARRL VHF contest and that try
was quite discombobulated. Since then, here is what has changed.
Antenna: the last event used a dinky 6 element yagi mounted at 50' on the TV
tower that is attached to the house. Since I live on the side of a hill,
this antenna has a reasonable shot downhill to the W and SW, but looks into
dirt on the uphill side to the E and NE. It was hard to make contacts in my
own grid in the dirt directions. I put up an identical dinky 6 element yagi
on a "real tower" that is taller and farther up the hill. This new antenna
is about 95' higher than the first one. It is above dirt in all directions,
but still not above the treetops up the hill to the northeast. The intention
is to stack the two antennas, but for now I had them both hooked up with a
coax relay in the shack so I could make comparative signal reports. Results
were as hoped. The high antenna was never worse in any direction. (But given
that its tower is higher and 250' from the house, its extra 4-5 dB of
feedline loss means it is actually hearing better by at least 4-5 dB.)
Secondly, to the E and NE, it heard signals very well that were inaudible
(!!) on the lower antenna pointing into dirt; no I guess no surprise here!
Receiver: My 70cm radio is an FT-897 and it is deaf on this band. An ARR
preamp was added, but this necessitated building up a PTT sequencing circuit
for the T/R relays and amp to make sure it gets safely switched out of the
line on transmit, since the 897 has no separate RX input. I had tested out
this circuit with a cheap preamp before putting in the ARR one. Everything
worked fine; at the end of the sprint, the preamp was still working. (And a
side benefit of the preamp is it gets the receive hiss level above the
annoying com port polling noise that the 897 passes onto the receive audio.)
Amplifier: During the Jan contest, my converted 6155 amp's over-temp circuit
would trip out the HV if I CQ'd repetitively for a few minutes. The root
cause was traced to this circuit's trip point having been lowered when the
amp was converted to use an internally generated 12V supply instead of the
intended external 20V. Changed a resistor value, and the amp did not trip
out this time, even under hard use. Yeah!
For the evening, nothing broke, no mouse turds were noticed, no carpenter
ants came out of the amp, no Nikes were raised to the ready, and I still see
potential for further improvement.
Thanks for the Q's, and to the sponsor,
Chet, N8RA
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