At 06:48 AM 5/30/2009, Bob Bruninga wrote:
Other Car Tips: Convert from RG-58 to LMR-240-UF or RG-213.
I'd take that with a grain of salt. The length of coax in a car is about say 10 feet. The loss of 100 feet of RG-58 is say 5 dB? and the loss of fancy stuff might be 3 db? But the diffrence for only a 10 foot run is only .5 dB versus .3 dB or only 0.2 dB. Nothing at all to even consider compared to all the work it will take, and the lack of flexibility and trying to run something almost like pipe through places where a simple wire (RG-58) fits.
My lesson was learned 40 years ago when I go my first 100 lb UHF mobile rig (tubes) just after highschool. The boat anchor filled the entire trunk of my MGB. But the first thing I did when we go the lot of them in my club was spend a day replacing the 8" internal piece of RG-58 in mine from the Transmitter output over to the chassis connector with a 8" run of RG-8. It was hard work getting that 8" piece of RG-8 coax inside the radio and routed all around the internal chassis.
The elmer at the time laughed. He said you just wasted a day and all that work to save 0.01% of loss. So now your radio works at 100% where as before it worked at 99.99%. Losing 3 dB of course is one thing (50%), but trying to worry about that last 1% when the effort is tremendous is just not effective.
Anyway, just my 2 cents...
Bob, Wb4APR
Yep. Commercial NMO mount mobile VHF/UHF antennas typically come with 17-feet of RG-58 and a connector to install when coax is trimmed for the particular installation. I have way too many 100w mobile installs in my past ;-) Of course, FM repeater design is for overkill on signal margins so no one sweats coax loss for mobiles.
The repeater sites may see 100-150 foot hardline runs, though. I have one 120-ffot tower with 17 antennas and the coax are 1/2 or 7/8 inch Heliax with the longest run 180-feet.
73, Ed - KL7UW