Our VHF Repeater-VU2BCM located at a height of 4000feet MSL with a coverage of 200km radius in the plains down, was having so many problems after the shifting to a new QTH nearby.
The equipment is an old Yaesu FTR 2410 ( Pl. do not laugh at us!) with 4 cavity Wacom duplexer on 145.650 -ve shift. Whatever be the new generation equipments this one served the HAM community for more than 20 years, as the best and popular repeater, without any major or minor complaints. Never the equipment behaved the wrong way. But after the change of the QTH to 20 feet away, all the Rx sensitivity lost and on weak signal motor boating or machine-gun fire made the installation useless. Then we ventured into probing the RPT builer archives and with the available information, we made one more visit to the site day before Yesterday. We changed the antenna to Diamond F22( earlier it was X510), changed the coax feeder, changed the Repeater to Kenwood TKR 720 ( No ears! Please help us with our other mail on this), Then looked around the Patch cords, all he connections to the duplexer checked. Power at the RPT TX out with Diamond SX 400-> 10Watt.The output to the antenna is measured to 6Watts. All fine but the early problem on weak signal was persisted allover this trials! Finally the suggestion to try a different length of the Patch cords came out and since the problem was with the RX we tried all possible combination lengths. No success. As the last try before close down- changed the TX patch cord-Distant weak station came in with out any gunfire! A small added change in the length created less sensitivity. We made an exact length of the good patch cord and tried that also worked fine. Put the old one-motor boat came back!! A small patch cord in the whole system- which looks fine, tests fine created all the discomfort! We also reduced the RPT TX power to 3Watts!(earlier 10Watts) The standard S meter reading of full scale came down to less 4 points in most of the reports from the users, but no one complained about any access issues- improved the RX sensitivity and audio quality! Hope the above will help others also in sorting issues related with RPT sensitivity. Before looking into the RX, go to the TX path. PETER VU2PJP
