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[TowerTalk] Too much antenna?

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Subject: [TowerTalk] Too much antenna?
From: (
Date: Sun, 17 Feb 2002 10:32:30 EST
For 40 meters I now have a HF6V @ 10 feet with 4 elevated radials for 80 and 
40, and my TH-7 boom @ 65 feet converted to 40 with an Omega match per N4KG.
Rig is an IC-765. Although both antennas are tuned to the CW segment of the 
band there is enough difference between them that I have to retune the radio 
when changing antennas. I find an "clear" freq near the center of the 
segment, cut the power to 5w and go to RTTY mode. The 765s internal tuner 
quickly matches either antenna. I then crank it back to 100w and away I go.
The problem I'm having is the TH-7 conversion makes my shack RF city at 100w 
on 40m.

During the ARRL DX CW contest I was S&Pn JAs on the vertical quite 
successfully until the sun was above the horizon when even the KW JAs became 
hard to copy and they couldn't hear me at all. Still S&P I thought I heard a 
VK5 with a big pile up going.
I switched to the TH-7 boom, tuned it as above and got distracted by the XYL 
for a bit. When I got back to the radio (about 5 minutes later) I could just 
copy the VK and he was just working US west coast stations, although there 
were many east coast guys calling too. I decided to give it a shot and 
dropped my call. He came right back to me (I'm in TN) through the pile! 
During my exchange I noticed no RF at all on the monitor. I was still at 5w 
After bit of playing I found that the monitor went nuts at 10w, but was FB at 
5w. I was still having trouble copying the rapidly fading JAs but they were 
coming right back to me at 5 - 7 Watts! I had NO copy at all on the vertical.

Anyone have any idea what's going on here?

I've checked EVERTHING that I can think of and everything seems fine. I put a 
coax choke at the antenna, but it didn't make any difference at all. The 
tower's about 40 feet from the radio, the TH-7 proper and the conversion have 
seperate RG-213 feeds with the coax shield grounded at the antenna and the 
bottom of the tower, they then run a couple of inches below the ground to the 

This thing should ROCK at 100w, but the computers won't handle it --- They 
make a thumping sound on CW and just lock up on SSB. Running QRP there is no 
indication of a problem.

Maybe this thing is just toooooooo much antenna for LP? I'm suspecting the 40 
feet from the radio is the problem, but don't have a solution. Moving either 
the tower or the shack is out of the question.

Thanks in advance for any help,
Don - K4BEV

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