> The local repeater is running 30 watts on 146.85 to a DB-224
> at about 125 feet. The link is on 145.11 10 watts to an
> 8-element beam at about 70 feet.
How good is the path between your site and the target repeater? If it's
LOS, you can probably put a pad in front of the link receiver and still have
a usable signal. Just throwing out rough numbers here, assume the distant
repeater is 100 watts ERP (+50 dBm). The path loss on 2m is about 109 dB
for 30 miles. We'll assume a worst-case scenario of your link antenna
system being unity gain (i.e. assume the antenna gain is offset completely
by the feedline loss). If you need, say, -80 dBm for a full-quieting
signal, you could put a 20 dB pad on your link receiver with no ill effects,
and likely take away the majority of the desense caused by fundamental
overload from your repeater transmitter.
If you really want to play with stubs (notch filters), I'd suggest getting
the largest-diameter scrap of heliax you can find. You will get a much
higher-Q notch than you would as compared to using something RG-8-size. It
will be difficult to cut the Heliax in such small increments to do fine
tuning - here's a way of getting around that problem. Incrementally cut the
heliax until you have the notch a little HIGHER than the frequency you're
interested in notching (146.85). Then, crimp the Heliax slightly, bringing
the shield closer to the center conductor (but not shorting!) , at the far
(open) end of the stub, to lower the resonant frequency as a makeshift way
of field-tuning.
--- Jeff WN3A
