I take care of several repeaters both commercial and amateur. I would choose a two antenna system any day over a single antenna using a duplexer. Of the 7 ham repeaters that I assist with, only 2 use a single antenna and duplexer, and this is due to tower space limitations.
My favorite way to do this is anywhere from 50 to 70 feet or more vertical separation, a 8 to 12" pass can on both transmit and receive, an Angle Linear preamp on the receiver if the noise floor of the site allows the overhead, and an isolator on the transmitter if there are any other nearby transmitters. Putting the receiver on the top antenna is the preferred method. I have had to receive on the lower antenna on one of our sites due to our top antenna being close to a FM transmitter with 80 KW ERP. Due to the surrounding terrain I have not noticed any change in coverage in swapping the receiver to the lower antenna on this site, but the receiver is much happier being further away from the high level of RF. I was involved with the first ham repeater our club installed in 1972, it was then and still is today a two antenna system. Can not knock 35+ years of good performance. Good Luck with your project. Joe - WA7JAW --- In Repeater-Builder@yahoogroups.com, "wb0goa" <aero...@...> wrote: > > Have chance to install a DB 224 at 450' and another one anywhere below it. > Using LDF6 on both runs. RF solid state 110 watts out. Wanting to know the > pros or cons of running both antenna close together for more height with > duplexer or spacing antennas for isolation without duplexer? >
