At 1/20/2007 08:42, you wrote: >Hi all, > >I've been working on this problem for a while and have not come up >with any good solutions. So I'm hoping to find someone that has "been >there, done that" with some suggestions. > >The issue is that I want to add a same-band remote base to an >existing repeater. The main problem is that the remote base is a >transceiver and I can't find a way to provide proper isolation >to/from the repeater. > >Here are the frequencies, but it looks like it really doesn't matter >all that much. The repeater transmits on 443.300, receives on >443.800. We're using a typical UHF pass-reject duplexer with about 70 >db of isolation between those two freqs. The remote base will >transmit on 444.225 and receive on 449.225. > >I can put two antennas on the tower, but my horizontal space will be >less than 20 feet.
That's not going to help much unless you use a Yagi for the rmt. base antenna & put the side null into the rptr. ant. You really need vertical isolation. >If the remote base had a separate tx and rx, then a band pass can >with a notch can (on the repeater freqs) on each side would probably >work fine. > >Anyone have a good solution? A friend of mine actually brought the RX input of a Kenwood TM-241 out separately so it could be connected to a community RX antenna some 60 ft. away from the 2 meter repeater TX antennas. We were also able to add an isolator to the TX (to be a good neighbor) & filters & pads to the RX line until the IMD dropped to minimal levels. The 241 has rather poor dynamic range. Bob NO6B
