Topband: YCCC 9 circle preamp failure test

[Lee STRAHAN]

Hi Guys,
  Assuming your verticals have a very good insulator there is NOTHING to stop that input capacitor from charging to very high like kilovolt static voltage levels. What I don’t understand is why leakage in that capacitor would cause any trouble or differences if it were not even there.  All that would happen is the vertical would assume about 5 volts DC on the elements. This problem rearing its head would indicate the vertical insulators or something in that path must be compromised as well. Or is the 8055 possibly going in to oscillation with a leaky connection to the element.
  Something does not add up here.??? What is the clue that tells you the capacitor has failed. Lack of performance/directivity or noise. Noise might indicate oscillation. 
Lee   K7TJR
Hi-Z Antennas



-----Original Message-----
From: Topband <topband-bounces at contesting.com> On Behalf Of VE6WZ_Steve
Sent: Tuesday, September 24, 2019 11:09 AM
To: topband <topband at contesting.com>
Subject: Topband: YCCC 9 circle preamp failure test

Yesterday I decided to measure the actual voltage at base of my short HI-Z verticals while I transmitted on the TX array.

Since I first posted about the coupling capacitor failures in these units, I have received private emails form 4 others with the same problem.

My question is what has caused these failures? Is it a lightning event,  is it high-potential wind static on the vertical elements or is it from TX RF overload.

TX overload seemed possible at my location because my array is less that 100’ from the TX antenna.  I built a diode detector probe and in the field measured the actual voltage when TX.  The results indicate at most I see 50 v at the pre-amp.  The coupling caps are 63v rated units.  This would indicate that RF overload is not the cause, but I would really like thoughts and opinions from others.
I have redesigned the amps to include a relay to short out the antenna when not powered up, so I feel I am protected from any cause.

Here is a link to a YouTube video that shows the test set-up and the actual measurements I made in the field.  I also talk about using gas discharge tubes as a remedy.

https://youtu.be/TmM_YnLob68 <https://youtu.be/TmM_YnLob68>

73, de steve ve6wz

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