First of all, your RX antenna should be at the top of the tower, with the TX antenna mounted below and directly in line with it. According to my CommShop for Windows program, you need at least 71 dB of isolation between RX and TX, and that calls for at least 35 feet of separation- which you don't have.
Since a repeater's range is determined primarily by how well it receives and not by its power, your repeater is crippled by both a reversed antenna situation and a poor RX antenna location. Desense is probably a factor, as well. Lose the mag mount antenna and install a good mobile-notch (as a minimum) duplexer to share the Celwave antenna at the top of the tower. For best performance, your feedline should be at least 1/2" Heliax, and all jumpers between the repeater and the duplexer should be double-shielded cable such as RG-214/U or RG-400/U without any adapters or barrels in them. You will be amazed at the improvement! 73, Eric Lemmon WB6FLY -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of agrimm0034 Sent: Saturday, August 01, 2009 10:36 AM To: [email protected] Subject: [Repeater-Builder] duplexerhelp or a good recomendation I am using a UHF GMRS repeater without a duplexer on 40 ft of tower. I use 2 antennas one of a Celwave 6 dB gain on the top as a tx antenna, and one 15 ft up off the ground mag mount to use as a rx antenna. The tx radio is a 45 watt and the rx on the rx radio is .35 uV sensitivity. It seems to me that I don't have enough isolation between the antennas and often have trouble getting through the repeater. Am I out of my mind to look into getting a celwave duplexer or is there any other ideas that would fit my needs?
