I'm attempting to design a system that will have a VHF repeater (freqs not yet determined) sharing an antenna with 2 packet radios (APRS on 144.39 and Winlink on 145.05, either of which may be active as a digipeater at any time).
I'm currently considering a bandpass-only "quadplexor" to isolate the radios from each other.. each radio running through a bandpass filter tuned to its frequency only (that includes the transmitter and receiver for the repeater), on the theory that it is a lot easier to pass one frequency than it is to reject 3 others. Assuming that none of the transmitters run more than 50w, how many DB down do I need to be outside of the passband to minimize desense for any of the 3 receivers ?? Any other suggestions on how I might handle this hookup would be greatly appreciated. I'm nearing completion my trailer-mounted 40ft crank up tower, and I'm having some problems budgeting space for a filtering system with 12 bandpass cavities without cutting into general cargo space.
