Multiple Repeaters, 1 Antenna

[libuff]

I'm sure this is simple, and easily searched (i just didn't know what to search for), but heres what I'm trying to figure out:

I currently have 1 repeater on top of a particularly large building, the roof space is at quite a premium. I would like to utilize two or more repeaters on 1 antenna. i am trying to get a frequency licensed close, but what are the technical requirements needed to accomplish this, and what equipment is needed?

[abbylind]

If they are on the same band you will need a combiner. Generally you use 2 combiners though one for TX one for RX. You may need to add some type of notch filter(s) to keep the radios from getting into each other. I'd also add an isolator too, and of course lighting protection.

Fowler

[Jim202]

The other issue that comes up is the combining system gets very lossy. The cost will be dependent on the
frequency band that your using. The lower the band, the more expensive the cavities due to their size.

You can expect to loose at least 3 db per port on the TX side. You also would be advised to contact one of
the combiner companies to have them help in your quest. They will ask you what power level the TX units are,
if they are solid state or not, the exact channels you will be using and things like that.

Hope you have a pile of money, cause your going to need it for the combiner.

Jim

If they are on the same band you will need a combiner. Generally you use 2 combiners though one for TX one for RX. You may need to add some type of notch filter(s) to keep the radios from getting into each other. I'd also add an isolator too, and of course lighting protection.

Fowler

[RKG]

If all three stations are "in cabinet" (i.e., both transmitters and receivers), you will need a combiner/multicoupler/duplexer arrangement. Consult Tx-Rx, Inc. They do all the engineering for you, including a determination of whether your combination of freqs is possible. Very effective. Very $.

[Einstein]

I would also suggest isolators to prevent intermod.

[Batwings21]

You said you were trying to get close, but don't get too close you need to know the specs on your antenna, you neeed to know its freq range and get your two freqs as far apart in that range as you can. Tx rx systems will be the way to go, and if you can get a second antenna, you'll save 3db of loss. If you have to use only 1, you'll have more like 6db.

[libuff]

well since $$ is particualrly an issue, i'll be contacting that company and seeing what exactly this may cost...

another question, if we have a license at a location, and want to have that frequency transfered to another location with higher elevation, how difficult would that be on the FCC end of things?

[Batwings21]

It mainly would depend on how far away your co-channel users are. You should be able to get a licensing company or service shop to help with the forms; or if you want to try it yourself, I think you can do it online.

[Dan562]

I did a Sinclair combiner, with isolators and a duplexer for 4 individual UHF R100 repeaters at a well known International Horse Racing Track in the Chicago suburbs. This system also has multiple power dividers and 500' Radiax for better signal penetration within the building / stands and a RFS / Cellwave +5dB Gain Antenna fed with 1/2" Heliax mounted on the roof of the building. The Motorola R100 UHF repeaters have less than unwanted signal rejection when any radiating antenna or Radiax is mounted close to the individual units which I had. My system had roughly -5 dB RF Path Loss (31.62%) before the signal reached the first power divider and then out to the external antenna and the internal Radiax.

With the use of a common duplexer the Tx F1 through F4 frequencies had to be separated by 250 KHz channel spacing to maintain a reasonable Tx loss through the duplexer. I did not use an Active Rx Multi-coupler otherwise the Desense levels would have been even worst. If you're using the older Micor /MSR2000 / MSF5000 / Quantar stations, Desense should not be a problem in your RF application. This repeater system even with all of the RF Path Losses managed to cover the in-bound RF signal radius around the site of 4 miles using 2 Watt Handheld Portables. In essence select a well known reputable OEM supplier such as, Sinclair, TxRx or RFS and work with their applications engineering and you will do fine with a combiner system

Dan