Joe, Even if your FR-4000 is the correct split (450-470 MHz) for GMRS, it may require tuning of the receiver's front end before being placed in service. I learned the hard way, when I set up some Kenwood TKR-750/850 repeaters, that sometimes there are helical resonators in the receiver that must be optimized. The Icom unit may have a similar design in its front end. Check the service manual to see if such adjustments are required.
Even if no such adjustments are required, the FR-4000 may simply be incapable of avoiding desense from nearby transmitters- even if they are far removed in frequency. If the VHF transmitter on the same tower is on a frequency that falls in or near the range of 155.850-155.908 MHz, its third harmonic will likely desense your repeater's receiver- even if it is within the FCC specs for spurious emissions. You did not mention what type of duplexer you have, but if it is the mobile notch variety, that may be part of the problem. Since GMRS is on UHF channels with a 5 MHz split, mobile notch duplexers work just fine in most applications. The problem with mobile notch duplexers is that they have no pass selectivity at all; the only adjustment is for the notch. Even pass/reject cavity duplexers have only modest bandpass selectivity. Assuming the FR-4000 receiver is properly tuned, it may be necessary to add one or two bandpass cavities between the duplexer and the receiver to tighten up the selectivity. 73, Eric Lemmon WB6FLY Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/