UHF help required

[Die Judicii]

Hi all,
I'm about to replace my bull bar mounted fibreglass UHF antennae. (the old one is Roo Ted).

When I fitted it, there was excess length in the coax cable and I just concertinered it all up and squeezed it up into the dash.
My question is,,,,,, for the new one,, can I cut the excess out of it ?

Or are they a "tuned" length, and must stay as they are ?

Cheers,

[deye243]

Having a tuned length is better but if you want to shorten it go ahead just do it in multiples of 68 centimeters as that's roughly the wavelength for 477 mhz ( but it is not critical it's up to you) I think most of the coax these days comes with the smaller TNC connector that'll go into the pl259 so you can thread your coax through small hole doesn't matter you can just use an ordinary solder on not a crimp pl259

[on_one_wheel]

Not a problem with UHF, the wavelength is so short that tuning coaxial cable length isn't necessary.
It's best to just run the shortest possible length.

[Wapiti]

Mate, as already said, shortening the cable will not affect the performance of the unit.
Of course, making sure the re-connection of the plug is done right and not shorted, but you won't have any dramas doing that professionally!

[niteowl]

Having a tuned length is better but if you want to shorten it go ahead just do it in multiples of 68 centimeters as that's roughly the wavelength for 477 mhz ( but it is not critical it's up to you) I think most of the coax these days comes with the smaller TNC connector that'll go into the pl259 so you can thread your coax through small hole doesn't matter you can just use an ordinary solder on not a crimp pl259

Sorry mate but your wave length in this case, for the UHF CB is not applicable, as this coax (which will be RG58 solid dielectric) has a velocity factor of around 65, not as calculated with the formula for wave length. ie 300 divided by the frequency in megahertz.
Regardless, the coax never needs to be a "tuned" length except in some special situations for some and only some 27 Mhz marine "mobile" antennas, due to their specific design.
Any way the length will not be relevant, for your mobile antenna is generally 3 m to cover most installations. Yes the shorter the better but only from a loss factor, although the length at this length will never be a problem.

Sorry about the lesson but I spent 40 years as a radio comms. tech and owned and ran my own radio business.

[Die Judicii]

Thank you gents,,,one and all.

Two things I hate.

> Trying to delve into something I'm not well versed in.
and,
> Finding myself in situations where I have to.

[Die Judicii]

On my old antenna I had put a short piece (ring) of yellow shrink wrap 50mm above the highest point of my rig, so as to be a visible height gauge for when entering low clearance carparks,,,, or driving under tree branches.

The new antenna is going to be considerably lower and useless as a height gauge so I cut the top off the old one at the height marker and put it on the spare antenna mount of the bull bar.
Might look a bit silly,,,,,, but at least it serves a purpose.