help on upgrade

[brin831]

guys we have a mototrbo xpr 8400 repeater running just 4 watts in a mobile duplexer running analog ... for now ... having issues with desense ... our supplier has spec'd a new sinclair Q3220 or a Q301GC used duplexer they have available. my question is this ... is the larger duplexer worth the additional size and cost. Do we just need a preselector to filter out the rx side ? lots of other uhf in the area much stronger and bothering us.

thanks for any simple recommendations ... the issue being that at different times of the year we have different events in with hundreds of additional radios they can come out and test and say yes this will help solve your problem now but may not in the future i've been reading as much as i can and spec wise the larger duplexer provides greater isolation but does it filter out enough adjacent noise that much better ?

i know without tests there is no way of really knowing but this question is a general ... in everyone's well informed opinion what would you recommend if you were spec'ing a system.

 

[kayn1n32008]

Get the Q3220.

 

[12dbsinad]

The first thing would be a real duplexer, not a mobile duplexer. It may require some notch/bandpass cans. Like you said, this is almost impossible to diagnose on the internet. You'd need to find the frequencies in use at the site and how they will affect your frequency/equipment. This is where site management comes into play. We have some prime sites around me that are well managed as far as users/frequencies/equipment are concerned. Then we have the free for all's, allowing anything and everything. NOTHING can be skimped at a high RF site.

 

[N1GTL]

The first thing would be a real duplexer, not a mobile duplexer.

THIS! Typically those mobile duplexers are notch only, no pass. I wouldn't spend money on a preselector until you have a real duplexer in and still see a problem.