[VHFcontesting] Polishing the Yagi

[Chet S]

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 at contesting.com> On Behalf Of John Young via VHFcontesting
Sent: Tuesday, December 25, 2018 7:08 PM
To: vhfcontesting at 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
_______________________________________________
VHFcontesting mailing list
VHFcontesting at contesting.com
http://lists.contesting.com/mailman/listinfo/vhfcontesting