Hello,
Well here is one that cant be figured out locally, thought I would
throw it to the experts. My high school radio club has recently made a
few upgrades to our VHF repeater. We replaced the Ringo Ranger antenna
with a Comet GP-9 Antenna, replaced the 9913 coax with Andrews 1/2''
Heliax, and put a Mirage Pream inline. The problem we are having is
mainly with the preamp (I think)
I will describe the setup and give all the specs first. The repeater
Rx and Tx is from a 110 Watt Motorola Mitrek power out from the Mitrek
is 50 watts. The power supply is an Astron RS-70M, Duplexer is a
Sinclair Q202G (yes, it is properly tuned and working as it should)
the antenna is rooftop on the schools theater building (the roof is
about 75 feet AGL and the antenna is on an 8' mast pipe) there are no
obstructions for at least 5 miles around. The preamp setup is as
follows, it is after the duplexers and before the reciever. We have
the preamp directly connected into the duplexer and a jumper going
from the preamp to the Rx bulkhead on the repeater cabinet. The preamp
has two settings, a higher gain and a lower gain setting, initially we
had it setup to the higher gain setting but I went up today and
switched over to lower gain and turned the power output to 30 watts.
The problem we have is the Rx is not what is should be. It is a tad
worse then when we were running the repeater at 15 watts without the
Preamp. I would really like to get the preamp to work like it should
in the repeater system, I just dont have any ideas on what to do next
to get better sensitivity on the machine. Any thoughts and ideas would
be appreciated. Thanks.
Alexander KG4OGN
P.s, all jumpers are made with double shielded ridgid coax, so thats
not the cause of the problem.
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