Rich, The short answer is: You need to find a bigger duplexer. Four 8" cans would work well such as a Wacom WP-641. You could simply call and order one if Wacom was still in business. (RIP) Unfortunately Tx/Rx bought them years ago for the name and to quash competition. They can be found occasionally for around $600 or so on the used market.
Other alternatives are as follows: 1) You can use two antennas and split the 639 duplexer so that 2 cans are in series between the TX and the TX antenna, and the other two are in series between the RX and the RX antenna. Terry WX3M a list member is doing this with VERY good results on one of his VHF machines. Of course this involves the expense of additional feedline and a second antenna. I think you said you had this machine on an 80' mast. 50' or so of vertical isolation coupled with the additional isolation of splitting the duplexer *may* be enough isolation to get rid of all the desense. TX goes on bottom, RX on top. 2) Buy additional Band Pass / Band Reject (BPBR) cans. You can add these additional cans between the Tx and/or Rx and the duplexer. These cans will give additional isolation. Even if you can find just Pass or Notch cavities, tune them and put them in the correct place. With both of the above options, you are looking to add to the isolation between your transmitter and receiver. You'll find you'll do best by adding cans to your transmitter that notch side-band noise at your receiver's frequency. In other words, do what you can to insure your receiver is not hearing your own transmitter's sideband noise on it's input. Pass cans tuned to the TX frequency or NOTCH cavities tuned to your *RX* frequency placed in the transmit line are your best hope. Good luck, Scott Scott Zimmerman Amateur Radio Call N3XCC 474 Barnett Road Boswell, PA 15531 On 9/8/2010 9:52 PM, Richard Kelly wrote: > > > Hello again Ken, > > Thank you for replying with more info, we appreciate it. My email > address if you want to get off this posting is w2...@arrl.net > <mailto:w2...@arrl.net> > > How would we go about providing MORE isolation than what we have done so > far? > > Rich Kelly W2RRK
