Is the preamp in a shielded box?
Is the power to the preamp via a feedthrough capacitor?
How does the repeater perform without the preamp?
What does the transmitter look like on a spectrum analyzer?
How does the repeater work with a simple 1/4 wavelength vertical?
Is all of the cable going into the duplexer, from both the transmitter and
the receiver, double shielded (RG-214/U or better)?
The MITREK shares a common board between transmitter and receiver making
duplexing difficult without desense. HOw does the repeater perform using a
second MITREK as the receiver?
Some ideas as to where to look.
Hope you find the problem.
73
Glenn
WB4UIV
At 10:18 PM 05/20/05, you wrote:
> 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.
>
>
>
>
>
>
>
>Yahoo! Groups Links
>
>
>
>
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