At 2/7/2005 02:30 PM, you wrote:
>Hi folks
>
>Imagine this scenario. 2 quality, UHF repeater colocated at the same site.
>Both repeaters are higher power ( > 50) out of duplexers, duplexers are
>high quality BP/BR types. Here's the kicker - they're spaced 25 Khz away
>from each other but not inverted from each other.
>
>Now, theory is one thing as to the interference potential without resorting
>to mulicouplers and combiners. But what is the real world problem
>potential? Anyone want to take a stab at this one?
I've seen more than the expected level of IMD problems for some reason when
dealing with close spaced TXs. There is one site around here with 2
repeater outputs 20 kHz apart. When both are up they sometimes 3rd
order-mix 20 kHz below the lower output & 20 kHz above the upper
output. When present the mixing products are strong enough to be heard 10
miles away. Both systems allegedly have the proper filtering/isolation in
place, so I suspect the mix is occuring in a passive (chain link fence,
tower joint, etc.), which would explain why it comes & goes.
Bob NO6B
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