Swapping Duplexers in one Repeater

[chuckhodge]

First, mods feel free to move this as needed - it didn't fit squarely in any forum.

I have two UHF licensed frequency pairs (450s and 460s) and a couple of old GR1225 repeaters with duplexers tuned to those pairs. The question is, can I move the duplexers over to my more modern ICOM repeater and a Motorola XPR I am looking to upgrade to without retuning? And let's say I decided to run one of the repeaters on GMRS frequencies periodically - can I just tune a spare duplexer to GMRS and swap it out for the one of the commercial ones? Ideally I would like to program the commercial pair on one channel of the repeater and the GMRS pair on another and swap antennas and duplexers if desired. This would be preferred to going the two antenna route.

I can't seem to find much feedback on how important it is to tune a duplexer to a specific repeater. From the looks of it there is no repeater involved in tuning and it is just hooked up to test equipment and tuned but wanted to get some feedback from the experienced folks on the forums.

Thanks in advance!

 

[mmckenna]

Duplexers are not tuned while connected to the repeater, so which repeater it's hooked up to shouldn't matter as long as the frequencies are the same.

As for swapping duplexers, that should be fine, just keep in mind that duplexers are sensitive to physical shock, so be real careful with them when moving them around.

 

[speedway_navigator]

If your new repeaters are the same freq it should work fine.
Most duplexer tuning by the mfgs is done with 2 port VNAs, vector network analyzers. It is critical to notch out the xmtr freq from the receiver. A 50W repeater is dumping that power into the duplexer which is trying to feed the receiver which can probably receive down to -120 dBm.
50W is 47 dBm so the difference is 167 dB which is about equal to cutting the transmit power in half 55 times in a row.

Most mobile duplexers are notch only to isolate the TX and RX freqs from each other.

 

[chuckhodge]

Duplexers are not tuned while connected to the repeater, so which repeater it's hooked up to shouldn't matter as long as the frequencies are the same.

As for swapping duplexers, that should be fine, just keep in mind that duplexers are sensitive to physical shock, so be real careful with them when moving them around.

That was my thought as well, thanks for confirming. Will likely have them tuned at a local radio shop shortly as one of them has some travel on it.

 

[MTS2000des]

Just remember that duplexer tuning can be affected by temperature and physical shock of transit. It's always best practice to tune on the bench then verify on site and retune if needed.

 

[chuckhodge]

Appreciate everyone's feedback. Info was what I thought, but good to get some reinforcement. My GR1225s have somehow lasted for years and are due for an upgrade. Good to know I can pull the duplexers out of them.