At 8/31/2009 06:33, you wrote: >Hi Guys, >We spent most of yesterday working on a UHF Mastr II Exec. Repeater, we >are using a TRAM 1481 Dual Band Antenna on. This is the high gain 8.3 dB >VHF/11.7 UHF. The system uses UHF Repeater, VHF Simplex, and IRLP. The >antenna works very poorly on UHF and much better on VHF. The SWR is about >3-1 on both frequencies. The antenna is not DC Ground and there is no >shorted connectors. Lack of help prevented us from taking the antenna down >and apart at this time. We ran tests by putting the antenna on a portable >and working a fixed base and again the VHF pinned the meter and the UHF >was weak, only a couple of S units better than the portable rubber duck. >Has anyone had a similar problem. I understand that the antenna is a >compromise and not as good as a single band folded dipole for example, but >several of us have these and they work great except for this one. I am >thinking there are enough Tram 1481 out there and someone may have had the >same problem.
I can't speak for the 1481 since I never had one, but I never had any matching or duplexing problems with the 1480 (lower gain 8' version). I also have a few Comet GP9s in service & they work fine, with advertised gain on both bands - no compromise. >Also there has been many posts about the LMR400 used in repeater service. >It is my understanding that the foil type should NEVER be used between >duplexers, from the TX, RX to the Duplexers, but I am not sure about >between the duplexer and the antenna. Comments please! You definitely don't want LMR400 any place where duplexed signals are present. This means between the duplexer & antenna. Not sure why it would be a problem for the TX & RX connections to the duplexer unless the connectors weren't installed properly, but then again why take the chance on a short jumper where loss isn't an issue? Silver-plated RG-214, RG-393, RG-223, RG-400, or RG-142 is known to be safe for that application. Bob NO6B
