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Topband: YCCC 9 Circle preamp failure

To: topband <topband@contesting.com>
Subject: Topband: YCCC 9 Circle preamp failure
From: VE6WZ_Steve <ve6wz@shaw.ca>
Date: Fri, 13 Sep 2019 12:55:20 -0600
List-post: <mailto:topband@contesting.com>
After 2.5 years of flawless operation, earlier this summer my YCCC 9 circle rx 
array started to develop some strange inter-mod noise, and random junk showed 
up on 160m when using the array.

I isolated the problem to be the .1 uF coupling capacitors on the input of the 
amps.  This happened on 4 of the 9 amplifiers.
The most likely cause is from TX overload because this array is only about 125’ 
from my parasitic TX array.  (the TX antenna is detuned when on RX and presents 
no issue on receive).
At first I suspected a nearby lightning strike, but the 4 failed amps happen to 
be the closest to the TX array, nothing else in the amp was damaged, and there 
was no other evidence of a lightning event at the station.

Here is a link to a YouTube video I made showing how I isolated the problem.  
Using my scope I show how the output from the damaged amp has significant phase 
and amplitude distortion, and using the multimeter the failed caps are 
evaluated.

https://youtu.be/t6oux3MStDw <https://youtu.be/t6oux3MStDw>

If you have one of these arrays, I show how it is very easy to test the 
pre-amps in the field using your multi-meter to confirm if a similar fate has 
occurred in your system.

73, de steve ve6w
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