Date: 03/29/06 02:38:29
Subject: [Repeater-Builder] Re: very close frequencies seperation
> "Ian Wells" <[EMAIL PROTECTED]> wrote:
> Hi guys .I am trying to receive 473.575mhz from a 25
> watt repeater ,line of sight , 50kms away and and
> re-transmit it on 473.200 at 25 watt on another
> site.The transmitt antenna is a 6db vertical ,9
> meters above ground and the rx antenna is a 6 db
> uhf beam 1-2 meter above ground ,aimed at the 473.575
> site Is it possible to notch out frequencies going
> into a receiver that are 275 or 375 khz off a uhf
> receive signal or is it going to be too close to
> filter out the TX .
Yes you can, but it won't be easy. You need as much
antenna system isolation as possible, a lot of how
the antennas perform is part of the equation, the
notch Q (quality, number and type), the transmitter
sideband noise and the quality of the receiver front
end (and 3rd order performance) are all factors in
how well the link system plays.
In addition to notch cavities, you'll probably need
band pass cavities on both the receiver and the transmitter.
RF leakage in various parts of the system can also cause
desense. You might also bump that UHF Beam up in size
(number of elements).
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