Camilo, Thanks for the kind words. Heliax is considered to be "bendable" rather than "flexible." Being copper, it will eventually work-harden after many flexings, and will likely fail due to stress cracks.
Although it is not cheap, both I and my local radio club use genuine MIL-spec RG-214/U coaxial cable on antennas that are moveable or rotatable. We leave appropriate slack to allow movement, and have yet to suffer a failure. The double braided shield of RG-214/U cable seems to survive years of movement. Perhaps other list members have a better solution...? 73, Eric Lemmon WB6FLY -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Camilo So Sent: Wednesday, June 17, 2009 7:27 PM To: [email protected] Subject: Re: [Repeater-Builder] Re: Need tips for repeater performance Hi Eric, I know you have been helping every one on this group. Can you please help a inexperienced person like me solve one problem on a crank up down tower here in Miami? Due to hurricanes, the tower have to goes down. What is the best choice of coax cable to use, because when the tower is down the coax length is loose so have to coil it and tie down to the tower? My question is what number of Heliax that is capable to roll it at a diameter of about 12"? Your recommendation is highly appreciated. Thank you. 73 Regards, W4CSO Camilo ----- Original Message ----- From: Eric Lemmon <mailto:[email protected]> To: [email protected] <mailto:[email protected]> Sent: Wednesday, June 17, 2009 9:34 PM Subject: RE: [Repeater-Builder] Re: Need tips for repeater performance 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: [email protected] <mailto:Repeater-Builder%40yahoogroups.com> [mailto:[email protected] <mailto:Repeater-Builder%40yahoogroups.com> ] On Behalf Of aisendwight Sent: Wednesday, June 17, 2009 6:11 PM To: [email protected] <mailto:Repeater-Builder%40yahoogroups.com> Subject: [Repeater-Builder] Re: Need tips for repeater performance --- In [email protected] <mailto:Repeater-Builder%40yahoogroups.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: [email protected] <mailto:Repeater-Builder%40yahoogroups.com> <mailto:Repeater-Builder%40yahoogroups.com> <[email protected] <mailto:Repeater-Builder%40yahoogroups.com> <mailto:Repeater-Builder%40yahoogroups.com> > > To: [email protected] <mailto:repeater-builder%40yahoogroups.com> <mailto:repeater-builder%40yahoogroups.com> <[email protected] <mailto:repeater-builder%40yahoogroups.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
