2 channel vehicle repeater/ duplexer

lunzac · Post by **lunzac** » Thu Oct 20, 2005 12:44 pm

hey guys
im installing a mobile repeater made up of 2 m120s into my vehicle using a duplexer and 1 single antenna. my question is this.....
i have 2 different frequency pairs that i want to be able to repeat, a commercial pair (once i get it liscenced and have the coordinator tell me which one it is going to be) and a GMRS (havent decided which one yet). i only want to be able to repeat on one frequency pair at a time, so tell me if this would work....

take the antenna port on both m120s and put a T adaptor on them sending one radio to the Tx sides of two seperate duplexers and the other radio to the Rx sides of the duplexer. also, on the antenna side of the two duplexers could i use another T connector and bring this all back to one antenna (an antennex phantom) that covers both frequency pairs. remember, i am only wanting to be able to use one frequency pair at a time and one duplexer would be tuned to the commercial pair and the other duplexer would be tuned to the GMRS pair.

-zach

tvsjr · Post by **tvsjr** » Thu Oct 20, 2005 1:51 pm

Umm, no way. May as well not install any duplexers... power would flow out the duplexer that does not have the notch (whichever of the two that is) and back in the other side. You'd have a loop.

The right way would be a combiner, but you probably don't want to put that in a vehicle. And the duplexer passband isn't wide enough to handle both splits.

I suppose you could do something sexy with a few coax relays to switch between two duplexers but it would be verry error-prone.

I do question why you want to have a mobile commercial and GMRS repeater. There's always the "because I can" logic, but I don't see much need.

lunzac · Post by **lunzac** » Thu Oct 20, 2005 2:05 pm

what about if i used two seperate antennas, one for each duplexer. still T on the radio side of the duplexer but then on the antenna side just have each duplexer go to a seperate antenna?

tvsjr · Post by **tvsjr** » Thu Oct 20, 2005 2:44 pm

You'd still have a loop.

Don't forget that repeaters are licensed at a certain place... unless you run low power and license it especially as a vehicular repeater, you're in violation of FCC regs.

EC-7 · Post by **EC-7** » Fri Oct 21, 2005 2:51 am

I'd say to get some coax A/B switches or use BNC connectors to quicly switch between duplexers.

I'd think it would be ok to use a T connector at the antenna side, going to oth duplexors and either a switch on the TX and RX to the radios or BNC quick release connectors. I'm no duplexer and antenna expert tho.

EC-7 · Post by **EC-7** » Fri Oct 21, 2005 2:56 am

I'd say to get some coax A/B switches or use BNC connectors to quicly switch between duplexers.

I'd think it would be ok to use a T connector at the antenna side, going to oth duplexors and either a switch on the TX and RX to the radios or BNC quick release connectors. I'm no duplexer and antenna expert tho.