Which would you use?

[JamesBrox]

I'll try to make this as detailed and as short as I can. My current set-up in the shack is two external/outside antennas. One for the repeater and one for base.
The first antenna is an Ed Fong DBJ-UHF GMRS w/ 50' Messi & Paoloni (M&P) coax about 43' above elevation. It's my repeater antenna. The repeater is an all-in-one unit with the duplexer (Bridgecom BCR-40DU), it has two 40w radios inside.
Second antenna is a Comet CA-712 EFC w/ 25' of M&P coax about 20' above elevation....this is for a KG-1000G+(50w) base unit.
I understand that duplexers take at least half of the power away. Got it.....nothing I can do about that. I ran a test with a SureCom SW-102. Correct, this is not a "high-end" tester. I do this for a hobby. Here's what I got.

RPT-SWR-DL(Dummy Load) = 1.01 w/ 22.3watts
RPT-SWR-Coax(50')-Ed Fong= 2.8 w/ 17.7watts
RPT-SWR-Coax(25')-Comet 1.2 w/ 22watts

Base-SWR-DL 1.1 w/ 46.7watts
Base-SWR-Coax(50') Ed Fong 2.0 w/44.6watts
Base-SWR-Coax(25') Comet 1.6 w/ 44.5watts

I understand that I've opened myself up to a lot of criticism and that there's a lot of variables, but which one would you put the repeater on and which one for base?

 

[mmckenna]

Well, it really looks like the repeater is happier with the Comet antenna. I'd use that.

I'd also look at the duplexer internal to the Bridgecom repeater. They are not great, Chinese flat pack with no so wonderful specs, but you should be seeing a bit better than that. Having someone tune them for the exact repeater pair you are using would be a good idea, they claim 1.5dB of insertion loss. Ordering them tuned and having them shipped often results in them getting knocked around and detuning.
You can also adjust the power output from the front panel for that repeater. Might be worth checking the output directly at the jack on the TX radio deck before it goes into the duplexer.

I got stuck with a few of those repeaters at a remote site. I tuned the duplexers once they were installed on site. But I'm only running the at 10 watts per the license.

 

[jeepsandradios]

As I said in the other forum buy a real antenna. I dont understand the fascination with ham built junk on repeaters. The antenna system is the most important part of the repeater. Buy a quality LMR antenna and good feedline and the repeater will work much better.

Also as @mmckenna brought up I'd have your duplexer looked at. Normally bridgecomm tunes it in the middle of the GMRS band and ships it. Having it looked at should help.

 

[KF0NYL]

I agree that you should double check the duplexer to make sure it is tuned correctly. My club just bought a Bridgecom repeater but decided to go with our own duplexer. We had a spare duplexer for our 70cm repeaters that we tuned specifically for the GMRS repeater.

You should also be able to tune the Ed Fong to get a better SWR reading. You will need something better than a Surecom to tune the antenna though. Check to see what frequency the antenna is resonant at and adjust accordingly.

 

[MTS2000des]

Duplex operation (transmitting into the same antenna while receiving) requires much more precision when it comes to tuning of the duplex filter itself, feedline, antenna and grounding. All play a factor in performance. A base radio can work just fine on a low rent antenna and cheap coax and produce acceptable results.

Expecting your two 40 watt radios in a box to play nice and not interact with each other using bargain basement components and guesswork tuning is just a time vampire that won't amaze you or anyone.

Proper duplex setup means on site tuning with a proper tracking generator after determining receiver itself is actually functioning to spec. Usually done using an ISO-T. Your antenna and feedline are part of the duplex filter system and WILL affect filter tuning. No way to do it other than right but what do we know.