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@contesting.com> On Behalf Of VE6WZ_Steve
Sent: Tuesday, September 24, 2019 11:09 AM
To: topband <topband@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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