ok cb people I am new but learning
?
does the antenna cable length matter? short as possible or is it like a wavelength issue where it is a certain length for a reason?

 

If Im not mistaken, the length of cable does matter.
I believe its due to the wave length but Im not 100% positive.
Thats why when coax is supplied with coax its 18' in length.
Also, if adding coax do it in multiplise of 9. ie 9, 18 etc.
Hope this helps.

 

cool thats what i thought

 

234 / freq X 12 gives a 1/4 wavelenght antenna.

IE 234/27.185 X 12 = 103.29"

For Coax you need to find the velocity factor for that coax. most RG/8 and RG/58 have a velocity factor of .66, So 103.29" X .66 = 68.17" for 1/4 wave of .66 velocity factor coax.

 

VELOCITY FACTOR (VF) OF COMMON COAXIAL CABLES


CABLE VF
RG-8 .66
LMR-400 .85
RG-8X .84
RG-11 .75
RG-58 .66
LMR-195 .83
RG-59 .82
RG-62 .84
RG-174 .66
RG-213 .66
RG-214 .66
RG-217 .66
RG-218 .66
RG-316 .79
RG-400 .695
LMR-500 .85
LMR-600 .86
1/2 HARD .81
7/8 HARD .81
LDF all ver .88

 

Okay, scarp, I have no idea what you're talking about.

I'm interested in this also, because I've just re-routed my CB antenna cable, and I'm finding that I need another 3' or so to reach my radio.

I have found some fairly well-informed posts on the internets that seem to land on both sides of the fence -- i.e. 9' increments does/doesn't matter.

I think what I've learned is that yes, there may be some minute theoretical advantage to going with an even 9' or 18' cable length, but for all practical purposes, it does not matter at all.

I plan to pick up an extension tomorrow, re-tune (if that even makes a difference, who knows) and I can report back with my highly unscientific results

 

I have done some rreading as well and do belive you shoud be a foot abouve your Jeep to get the proper bounce of the radio wave. Correct?

And yes you sgould stay in the 9s thats how i understand it

 

1. The length of the coax could be critical if it's part of the antenna (radiating) system, or part of an antenna matching system (i.e., a balun). That's where velocity factor comes in.

2. However, for our Jeeps, the length of the coax is not critical because it's not part of the emitter (the antenna). Of course, shorter is better. However, I recommend making it a couple feet extra in length so if you ever change the rear configuration (say, add a swing-away tailgate with the antenna mounted to it), you're ready to do so without rerunning the coax.

--mark d, retired USAF CMSgt with 27-1/2 years of avionics maintenance and engineering background

 

Thanks Mark, that makes a lot more sense to me intuitively. I was scratching my head trying to figure out how the length of a run of shielded coax would have anything to do with tuning the setup.

This "9 or 18 foot" myth has really taken hold out there though, makes me wonder how that happened

 

It's electronics. And, worse yet, it's RF. Never trust intuition. It's just FM (fricking magic!).