Aisen, Changing the RG-8 to LMR400 will reduce the feedline loss by about 0.8 dB, which is a small improvement, but LMR400 is known to cause major problems in duplex service. RG-8 will have about 2.2 dB loss in 50 feet, and LMR400 will have about 1.4 dB loss, at 458 MHz. A far better choice would be Andrew LDF4.5 Heliax with 0.5 dB loss, or LDF5 with 0.4 dB loss. Lose the RG-58 jumpers, and replace them with good, double-shielded cable such as RG-400 or RG-214. These jumpers should be fabricated with the proper high-quality connectors on each end (no barrels or adapters), and should be no longer than necessary.
What is the make and model of your duplexer, and of your antenna? 73, Eric Lemmon WB6FLY -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of aisendwight Sent: Wednesday, June 17, 2009 6:11 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Need tips for repeater performance --- In Repeater-Builder@yahoogroups.com <mailto:Repeater-Builder%40yahoogroups.com> , "NORM KNAPP" <nkn...@...> Well, I guess this is called "A rookie decision"!!!. Sorry, it's been like 18 years since I had any contact with radio stuff (back in my days as WP4MPS) now I'm back at the commercial level and I see I've had a bad start (yeez!!!!) Well., I'll have to find some use for that cable. Ok, keep it coming please... wrote: > > BATTLE STATIONS!!!!!! RED ALERT!!!!!! > We got LMR-400 here! > > ----- Original Message ----- > From: Repeater-Builder@yahoogroups.com <mailto:Repeater-Builder%40yahoogroups.com> <Repeater-Builder@yahoogroups.com <mailto:Repeater-Builder%40yahoogroups.com> > > To: repeater-builder@yahoogroups.com <mailto:repeater-builder%40yahoogroups.com> <repeater-builder@yahoogroups.com <mailto:repeater-builder%40yahoogroups.com> > > Sent: Wed Jun 17 19:41:18 2009 > Subject: [Repeater-Builder] Need tips for repeater performance > > > > Hello everybody: > > I'm into increasing the performance of my repeater. I've already ordered 50 Ft. of LMR-400 to replace the cheap RG-8. Yet, I wonder if there is something else I could do. > > The Duplexer is pre tuned to my freq. (458.0 repeater RX / 453.0 repeater TX). The duplexer is connected to the radios (my repeater is built out of two Motorola M120's) using RG-58 jumpers of about 24 inches long. Could that be affecting performance? When I check the TX power thru the duplexer I'm getting about 10W yet the TX radio is programmed for 30W. I know that I'll lose some power with the duplexer, but seems to me that I'm losing too much. SWR won't go below 2.1 no matter how much I adjust the antenna bays. > > So, what could be done? I imagine that swapping the RG-8 for the LMR-400 will help but I still wonder if that would be enough. Any help will be greatly appreciated. > > Aisen
