Batboard

k, i'm getting coordinated for another frequency pair. i currently have a 451.350/456.350 pair. i'm going to get a 451.275/456.275 pair. i'm thinking about mounting these in the same cabinet and sharing one antenna for both. i'm not very well versed on duplexer specs, but is the channel spacing appropriate or is it too close/too far?

thanks

Your description is a bit vague .... Are there two physical repeater stations that will be simultaneously be in use or a two channel / frequency repeater?

Since you have only 75 KHz Tx to Tx channel spacing you will need what is referred to as a Hybrid Combiner System and it would not be a bad idea to have Dual Circulators / Isolators on each Transmitter leg.

If I were putting multi-frwquency transmitters on one antenna, I would try to separate the Tx Frequencies a minimum of 200~250 KHz and a maximum of 1 MHz to provide up to 4 or 5 repeater Transmitters. You would still need a Tx Combiner System w/ Duplexers and Rx Multi-Coupler to make the system work correctly. Any time you add Tx Combiner to your RF system there will be more RF losses involved. I would expect to see a -4 to -6 dB losses depending on how many Tx are installed into the system.

You may want to contact the Sales Engineers at the following web links:

http://www.rfsworld.com/index.php?p=1&l=1&fv=7&js=1

http://www.sinctech.com/

http://www.txrx.com/

thanks for the quick reply. yeah, that sounds like alot of money to spend and still get stuck with a -4-6 dB loss. these are going to be two completely independant channels on two separate MTR2000 repeaters. both in use by different user groups simultaneously. i'll just locate the 2nd channel at a different site down the street and save myself alot of trouble. thanks again.

My two bits worth:
I have built several such systems.
We used a ferrite hibred combiner with a 4 can Pass-reject duplexer.
The receive side had a amplifier and power splitter so several receive channels could be supported.

The ferrite combiner has 3 db loss for a 2 channel combiner.

I have several spares.