John,
The other culprit could be water in the connectors. Don't know if you are
using N connectors or PL259's but a little water in those puppies can go a
long way with SWR.
John K4SQC
On Wed, Dec 26, 2018 at 4:51 PM John Young via VHFcontesting <
vhfcontesting@contesting.com> wrote:
> Chet,
> I expect you are correct, the sudden change from the week before the
> contest where it would take a tune anywhere to about halfway into the
> contest where it barely worked at 51MHz was probably due to water in the
> gamma match. That felt like way to sudden a change to be due to slow
> oxidation. I will see what I can do to prevent water intrusion. Thank you
> for suggesting this. I knew I needed to address water in the gamma match
> it but have been afraid to touch it since took a full day of work with a
> spectrum analyzer to get set close to 50ohms and flat across SSB and FM. I
> will dive in and seal them up. If I get it wrong I know my buddy Jacek and
> his magic blue tooth remote head spectrum analyzer will get it dialed in
> next weekend.
> Jay,
> Thanks, I got very lucky with conditions and a great turn out from Hams on
> FM.
> You asked.......but who does that? Well I do, sort of. I keep Anti-Sieze
> on all hardware thats R&R'd, I also keep a die grinder and spare hardware
> on hand. I did have my 6m telescoping elements seize up January of 2017
> with ice so I now coat all my antenna's with silicon spray (including
> inside the telescoping tubes) before the January contest. The silicon
> spray is used to keep ice from forming inside the tubes locking the
> telescoping tubes together (I pull outers for transport). It also lets all
> antenna's shuck ice as it forms during the contests. 0300 UTC, 25 degrees
> and dropping, soaking wet, numb fingers, all alone on a mountain top trying
> to pack up with seized telescoping elements, ah the joyous memories we
> make contesting.
> Thanks guys. I appreciate the advice. Always learning.
> 73JohnKM4KMU
> -----Original Message-----
> From: Chet S <chetsubaccount@snet.net>
> To: vhfcontesting <vhfcontesting@contesting.com>
> Sent: Tue, Dec 25, 2018 9:01 pm
> Subject: Re: [VHFcontesting] Polishing the Yagi
>
> 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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