Hi John,
If this antenna has a gamma match, my guess is that water got into the gamma
rod, thus changing the effective series capacitance, and de-tuning the match.
73 and Merry Christmas,
Chet, N8RA
-----Original Message-----
From: VHFcontesting <vhfcontesting-bounces@contesting.com> On Behalf Of John
Young via VHFcontesting
Sent: Tuesday, December 25, 2018 7:08 PM
To: vhfcontesting@contesting.com
Subject: [VHFcontesting] Polishing the Yagi
In sept of 2017 a buddy came over with a spectrum analyzer and we dialed in the
vswr for my four low band Yagis to under 1.5:1 for FM and under 2:1 for SSB.
Everything was great through the weekend before september 18, though I did need
use the radios built in tuner for 6m going into sept 18.
Midway into the sept 18 contest I got rained on quite a bit and 6m vswr started
rising to the point where the tuner couldnt get the 6m vswr under 3:1 on 52.525
(which cut power way back) but I could just barely get a tune around 51MHz so I
QSY'd FM to there. No problems working SSB in the 50's using the tuner.
The antenna is a cushcraft 5el beam with telescoping elements. The smaller
tubes have wraps of tape on them for stops so I can disassemble for transport
and quickly assemble it.
Last week I disassemble the elements and found light oxidation on all the
mating surfaces. Using 220grit paper in a dowel rod as a flapper I polished
inside the tubes and then polished th outside of the small tube by hand with
220 grit.
Today I got around to testing. Without the tuner I got 1.5:1 @ 52.525 and was
able to 1.2:1 with the tuner from 50 to 53MHz. Hope to get to 1.1:1 on 52.525
after it gets hooked up to the analyzer.
Heard that polishing is an XYL's tale but I am a believer. Anyone had a
similar experience?
73
John
KM4KMU
Sent from AOL Mobile Mail
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