Dulles Repeater Fixed
fgentges at mindspring.com
Wed Jun 16 15:12:24 CDT 2010
We have had several repeater problems. They have been fixed and the
repeater is back on the air.
We were chasing down several problems, none of which were discussed on
the Internet. I had to find each solution on my own even though the GE
Mastr II is well covered. Craig Brown, Allon Stern, Rick Miller and Mike
Nowlen all helped with suggestions and encouragement.
1. Receiver sensitivity was down at 1.6 microvolts and shold be more
like 0.3 microvolts. After much effort we tried adding a 5 picofarad
capacitor across an 18 picofarad capacitor. That silly little 5
picofarads changed the sensitivity to 0.23 microvolts. That should give
us better range. Let us know if you are able to get into the repeater
from sites you could not do before.
2. We all were finding times when the repeater went into a mode where
it had really bad buzz at 60 hz., transmitted ID but did not respond to
input signals. We were puzzled by this problem that came and went.
Finally, Allon Stern suggested we look into the power supply. After
some thought, it seemed possible that one of the three big filter
capacitors was intermittently going open circuit and putting raw
rectified DC on the power amplifier. We placed three external caps we
had tested across the existing ones. This saved us the work of carrying
the power supply down in another trip to the building. Time will tell
if this is a fix.
3. The tone coded squelch being transmitted was way down from where it
should be. After some signal tracing we found a missing connection. We
do not know why but added a jumper wire and it fixed the problem.
I will be at Saturday's meeting and will give a summary of the problems
and try to answer questions.
The repeater is now returned to amateur service and encourage everyone
to once again use it. The repeater is on 145.31 with CTCSS tones of 77
Hz in and out. We have programmed the repeater to not transmit the
tones when it is doing normally timed identification on CW and voice.
This will let you put a radio in the shack and only hear the repeater
when someone is using it.
I feel bad it has taken so long as life and Hamvention went on and I
want everyone to get back into the habit of meeting on the repeater.
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