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Topband: Shunt tower feed question

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Subject: Topband: Shunt tower feed question
From: "James C. Hall, MD" <>
Date: Sat, 30 Oct 2010 18:13:25 -0500
List-post: <">>
Hello All:

New tower setup: 120 feet Rohn 45 with two large yagi's at the 120 and 60
foot level, both with 44 foot booms. The shunt feed is attached at the 55
foot level and the drop wire is about 4 feet off the tower.

I have a 10kV 500pf vacuum variable capacitor mounted at the base in a
Hoffman enclosure. Just with that, I could get to 3:1 SWR at 1823 kHz (my
chosen low point).

I have never set up a gamma match before but I had a couple of 50pf doorknob
capacitors rated at 5kV. One didn't do it, but with both in parallel I
managed to get the SWR to 1.3:1 at 1823 kHz. The bandwidth I have seems
narrow at about 40 kHz at 2:1 SWR points. So far I have just nine 60 foot

Any suggestions to this setup ? Comments ?

73, Jamie

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UR RST IS ... ... ..9 QSB QSB - hw? BK

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