Although it really only masks the problem, you can use CTCSS tone to avoid hearing the distant transmitter. Of course, the repeater you're linking to must encode CTCSS, and your link must decode it.
A more technical approach is to use a modest-gain Yagi antenna pointed directly at the offending transmitter, and adjust its position relative to your primary Yagi to develop a signal that is 180 degrees out of phase with the same signal that leaks into your primary antenna. The resulting signals are then combined to feed the link receiver. Although this solution works, and I have used it to cancel multipath pickup at television head-end sites, it is subject to changes in weather and varying power levels. Rather than actually move the sense antenna closer to or further away from the primary antenna, I used a phase-shifting device made for the cable TV industry. A less-expensive method is to experiment with varying cable lengths to find the appropriate delay. Obviously, you must prevent the link TX signal from getting into the sense antenna. But, before you put too much effort or money into the solution, try rotating your link antenna while monitoring the signal from the offending station, to see if you can find a null in the back pattern while still receiving the desired signal. You might also experiment with other directional antennas that have superior side-lobe rejection and high front-to-back ratios, such as a corner reflector. 73, Eric Lemmon WB6FLY -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of n2len Sent: Saturday, September 27, 2008 10:00 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] UHF LINK ANTENNA QUESTION HELP NEEDED! Can anyone please offer me some assistance. I am trying to link my VHF repeater to a club machine on 440 MHz. For now I received permission to link directly on their input until the club installs a remote base and Yagi next spring. Their repeater is about 20 air miles away. I am using a 5 element UHF Yagi about 45 feet up a 170 Rohn 65 at my hub site! The Yagi is facing due West. The link works fantastic with 5 watts however I am receiving a 440 MHz repeater on the same input over 100 air miles away to the South. 90 degrees off the side of the Yagi. So my question is. Any input to solve this antenna related problem to buffer that weak signal from the south? Any move of the antenna lowering, different antenna etc... Any ideas would be greatly appreciated....
