Best Mobile Coax

[ctvanover]

I know this has been asked before, but it's been a while since I've been on here, so here goes one more time.

Which is the best coax, the RG-58A/U or the RG8X (Mini 8)? I also need to know what would be the best length to use from the radio to a single antenna setup for mobile use in a Peterbilt rig?

 

[mackmobile43]

CQ
Lo-loss EXTRA FLEX 58

The WireMan - Coaxial Cable

As much as it takes to go from the radio to the antenna.

 

[ctvanover]

CQ
Lo-loss EXTRA FLEX 58

What is Lo-loss EXTRA FLEX 58? Where do I find it? Is this stuff that you're talking about, 129FF 58 CQ EX FLEX TPE from The WireMan - Coaxial Cable?

 

[bluestallion]

I'm using rg 213. Not the best flexiable coax. But i seems to work well. Just my .02

 

[hotrod]

rg 213 is way too hard to route for a mobile much less
a big rig. i reccomend LMR- 195 low loss rg-58 or lmr 240 for high power apps
most installs use 18feet .why? have no idea. i know it just works

 

[W5LZ]

From what you've said, I'd think almost any coax would work just fine, even RG-58U. I think as a general thing, RG-8X or RG-8 ought to be as good as any. That RG-8X is easy to work with, so would probably be my first choice.
Unless the run length gets to be more than 'normal' for a typical mobile installation, the amount of loss any coax feed line will present is just not worth worrying about.
The best length for a feed line is whatever it takes to get from here to there, with a little left over so you can move things around later.
- 'Doc

 

[Robb]

I like LMR-240 UltraFlex.
It is small, has a great velocity factor, is double shielded, and can handle up to 600 watts without a problem. You don't need a long run for a truck anyway, so just about anything will work.

 

[mackmobile43]

CQ
Lo-loss EXTRA FLEX 58

What is Lo-loss EXTRA FLEX 58? Where do I find it? Is this stuff that you're talking about, 129FF 58 CQ EX FLEX TPE from The WireMan - Coaxial Cable?

Yeah thats it, just give them a call and it's the same as lmr-240 at a LOWER price.

 

[triple nickel]

18' of coax was and still today the better choice on some mobile antenna's, Such as the Francis 5' and the Bronco buster also the Striker antenna. Some say 9' is just as good, But from my own comparison the 18' RG-58 worked the best. Also the Braided extra shield coax works better in a semi truck. These are my own comparisons from a 379 Peterbilt and a W-9 Kenworth.

 

[terryj]

You really don't need to worry about the line loss unless your are running your line a couple hundred feet. Line loss for RG-58 isn't that much at 10 or 20 feet. Seeing how coax line is an unbalanced line the lenght isn't that important if it is terminated correctly. If you are using coax line as a tuning stub then the lenght becomes very important, however, I don't see that happening in a typical install.

 

[radiohobby]

I always just buy a fifty or hundred foot roll and cut it to fit the job I am working on with a little extra for moving things around and then attach the pl-259s. Have always done it this way weather I am installing the old 102 whip and ball mount or the ones that use the pl-259 on both ends and the antennas have always had less than 1.5:1 swr on entire band. Just get a good coax and use solderon and not crimpon for best results.

 

[CDX-007]

I have always used 12' or 24' lengths of 66% VF coax because at 12' it is a non-resonant 1/3 wavelength which helps make it unattractive for RF feedback due to CMC, plus at 66% VF, 12' is ½λ so the phase angle at the antenna (180°) nicely mirrors that of the RF as it leaves the transmitter.

 

[W5LZ]

CDX-007,
I'm curious, how did you arrive at those electrical length figures? Those 12/24 foot lengths being both 1/3 wave and 1/2 wave at the same time?
- 'Doc

 

[CDX-007]

CDX-007,
I'm curious, how did you arrive at those electrical length figures? Those 12/24 foot lengths being both 1/3 wave and 1/2 wave at the same time?
- 'Doc

Hi Doc,

How did I arrive at those lengths? I kept finding that length stopped the RF feedback in mobile systems I helped with back in the '70s when almost all my friends had radios & amps.

It just works out that 12 FEET OF 66% Velocity Factor RG-213/RG-8/RG-8M is a 1/2 wavelength inside and 1/3 wavelength on the outside shield as the CMC sees it.

For longer runs 24' of 66% VF also works well as it's a full wavelength inside and 2/3 wavelength outside.

 

[WR0220]

I use LMR-240UF for mobile installs, but that's just my preference. It's easy to route, low loss, double shield and the outer casing holds up well for years of trouble free service.

Hi Doc,

How did I arrive at those lengths? I kept finding that length stopped the RF feedback in mobile systems I helped with back in the '70s when almost all my friends had radios & amps.

It just works out that 66% Velocity Factor RG-213/RG-8/RG-8M is a 1/2 wavelength inside and 1/3 wavelength on the outside shield as the CMC sees it.

For longer runs 24' of 66% VF also works well as it's a full wavelength inside and 2/3 wavelength outside.

I'm curious as well. If you have CMC wouldn't that indicate a tuning problem with the antenna? Wouldn't you see better results by adjusting the antenna rather than altering the coax length? I thought that CMC only traveled on the outside (shield) of the coax. How do you get CMC on the center conductor?