Multiple repeaters on single antenna?

[robertsdoug]

I’m in the process of building my first repeater, so please excuse the ignorance. I am familiar with a duplexer in that it will allow for a single antenna to be used for both transmit and receive. But, is there such a device that will allow for multiple UHF repeaters to be connected to a single antenna? Obviously, it is much more cost-effective to use such a device, if it exists rather than running multiple cables and antennas up a tower.

 

[kb5udf]

Yes. It can get a bit complicated depending on the site, but have a read of this:

http://www.repeater-builder.com/antenna/db/pdfs/db-about-combiners.pdf

Many more articles on repeater-builder

 

[prcguy]

Its very common at commercial sites to combine transmitters on a single antenna and receivers on another antenna. If frequency spacing allows you can combine them all on one antenna but gets expensive. Typically the master receive antenna goes at the top of the tower and the transmit antenna goes further down to achieve a needed amount of isolation. Then a master receive band pass filter is used to cover only the needed receive frequencies feeding a preamp then divider to all receivers. Depending on transmitter spacing a low loss combiner is used with ferrite/cavity types if frequencies are far enough apart and if they are close together a more lossy hybrid combiner is used.

 

[12dbsinad]

To expand on what PRC said about loss, I just worked on a system that had a Hybrid... 100w in and about 23-24 watts out to the antenna. Not very efficient, but it works

 

[mmckenna]

I’m in the process of building my first repeater, so please excuse the ignorance. I am familiar with a duplexer in that it will allow for a single antenna to be used for both transmit and receive. But, is there such a device that will allow for multiple UHF repeaters to be connected to a single antenna? Obviously, it is much more cost-effective to use such a device, if it exists rather than running multiple cables and antennas up a tower.

It's what trunked systems use. Multiple repeaters on two antennas.

It can be cost-effective depending on the specific situation, or it can be quite expensive. It also requires quite a bit of knowledge and planning to do correctly.

 

[jeepsandradios]

Use this setup on many of my UHF repeater sites. Normally 2-3 channels on the combiner with a second antenna for RX thru a multicoupler. As said most all trunking systems use this setup also. I have done this in VHF but the combiner loss normally is much more than UHF.