CALIFORNIANS ACHIEVE
NEW WORLD 75GHz DX RECORD
On
Friday, March 1,2002, we
completed several QSOs that we believe set a new North
American and new world record on 75GHz.
At 12:30pm PST W0EOM
completed a QSO from Mt.St.Helena, California (CM88QQ) to
KF6KVG on Mt. Umunhum (CM97AE) on 47.040GHz. Signal
levels were 20+dB out of the noise. Several
minutes later, W0EOM and AD6FP both completed QSOs from
Mt.St.Helena to KF6KVG on Mt. Umunhum on 75.600 GHz.
Once again signal levels were 20+dB out of the noise. The
distance from CM88QQ to CM97AE is calculated as 175.3km.
After several false
starts in arranging a record attempt, Will, W0EOM,
finally got everyone to agree to go out on Friday, March
1. Will and Gary AD6FP went to Mt.St.Helena, Bob KF6KVG
went to Mt. Umunhum and Lars AA6IW was in Los Altos Hills.
Previous tests indicated we might have difficulty with
paths longer than 160km on 75GHz so Lars was positioned
156km from the Mt.St.Helena end.
Arriving at Mt. St.
Helena Will and Gary found the traditional operating spot
in disarray. High winds the previous evening had caused a
tower to fall partially destroying the wooden deck that
is usually used by the local microwave crowd. The winds
were also still pretty high, estimated at 35 to 40mph.
After some exploration we were able to find a sheltered
spot out of the wind and set up the radios.
A quick try of the 10GHz
radio resulted in nothing heard from the local beacon or
Lars’ high power transmitter so we concluded the
transverter had failed. We were hoping to use the 10GHz
signals to determine bearings to Mt.Umunum so when the
radio failed things were looking dismal. Luckily Will
was able to find the signal from Bob on 47GHz with a bit
of panning of the dish. Once peaked up on 47GHz we had
a good optical target to use to sight the 75GHz dishes.
The 47GHz signal
levels were sufficient to allow Bob to complete the
exchange using NBFM rather than CW. After aligning the 75GHz
dishes on the same heading as the 47GHz dish, the 75GHz
signal from Bob was quickly located on the Mt.St.Helena
end. To our surprise, the 75GHz signal level was as good
as the 47GHz level! The two 75GHz contacts were quickly
completed from both W0EOM and AD6FP to KF6KVG. The 75GHz
signal from Mt. Umunhum peaked 23dB out of the noise with
6-8dB fades.
After working Bob on
75GHz, Will and Gary repositioned their dishes and worked
Lars, AA6IW, on 75GHz at 156 Km distance (this would have
previously been a 1km increase in the 75GHz world record).
Signal levels from Lars on the 156km path were comparable
but slightly less than the levels from Bob on a 176km
path.
The equipment used at
each station is as follows:
W0EOM: 47GHz: 60mw
xmit power, 2' cassegrain dish, 4dB NF rcv.
76GHz:
8mw xmit power, 18" cassegrain dish, 15dB NF rcv.
KF6KVG: 47GHz: >20dbm
xmit power, 2' prime focus dish, 4dB NF rcv.
76GHz:
10mw xmit power, 1' prime focus dish, 15dB NF rcv.
AD6FP: 76GHz: 4mw
xmit power, 3' cassegrain dish, 15dB NF rcv.
AA6IW: 76GHz: 4mw
xmit power, 18" cassegrain dish, 15dB NF rcv.
All the radios use LOs
that are locked to either precision OCXOs or Rubidiums.
Weather conditions
were very favorable for mm-wave propagation:
18% to 26% rel.
humidity along the path. 40 to 65 degree F temperatures
On the way down Mt. St.
Helena we could easily see the snow capped peaks of the
Sierras over 150 miles away. The unusually low humdity
as well as the clear atmospheric conditions were major
factors in making QSOs on this record path.
Best regards to all
from:
Will W0EOM
Bob KF6KVG
Gary AD6FP
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