What do I need to know in order to determine whether I can use this cable for the CB install?

MikekiM

MikekiM

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Installing the CB.

Was going to buy coax cable and shorten it as needed and then remembered I have a roll of high quality coax cable left in my house by the 'cable-guy'. I don't know much about cable specs but this is heavy gauge cable.. not the stuff you buy in the big box store.

What do I need to know in order to determine whether I can use this cable for the CB install? I have professional coax strippers and crimpers. The end fittings and weather sleeves can be found on Amazon.
 
Thank you!!

Estimate on how many feet I should buy to run from the center of the dash, along the drivers side rocker and up to driver side tail light mount for the antenna?
 
That 18' is important...it's the length of a AM wave in that frequency range. Shortening the cable will affect your SWR and the performance of the radio.

Avoid running the coax parallel to power wires.

Grounds are your friend.

-Mac
 
macleanflood said:
That 18' is important...it's the length of a AM wave in that frequency range. Shortening the cable will affect your SWR and the performance of the radio.
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That's nothing but an old wive's tale, really. It has been disproven countless times. Cable length is absolutely unimportant on the unbalanced type of antennas we use on our Jeeps. Not to mention 18' is not a multiple of the 11m (CB) band wavelength.

Here's a good article on the 18' cable myth... https://jeepspecs.com/tj-generation/18ft-coax-myth/
 
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macleanflood said:
Was just reading that... amazing how much info is out there...
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Don't feel like you got duped by that 18' cable length myth, it sounds very plausible to those with a little electronic education. It fooled me at first too despite having had quite a bit of RF and antenna theory training/education.
 
Here's another argument...I'm down for learning new stuff...and after watching the whole thing it comes off as a rambling rant.

 
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Interestingly enough those that tell you that you must run 18' feet do not have a good solution for the extra coax you do not need without creating an RF choke with it.
 
Blackjack said:
Interestingly enough those that tell you that you must run 18' feet do not have a good solution for the extra coax you do not need without creating an RF choke with it.
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Coiling the excess coax cable creates a negligible effect. Go to any large antenna 'farm' with lots of antennas like at an air traffic control site and virtually all of the antennas up on the poles have several feet of excess coiled up coax cable looped off at the top. Yes coiling a wire creates an inductor but coiling a short amount of RG58 in a Jeep is not going to have a significant effect. Not to mention the center conducted is surrounded by a braided shield that is grounded at both ends.
 
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Yup 18' or 118' is plain wrong. The wavelength in coax is also different than in free space like an antenna. Roughly speaking at 27MHz (CB radio), the wavelength in RG58 is 24' long and the wavelength in free space is 36'. But that doesn't matter at all.

RG58 is a conductor surrounded by a braided shield so length is irrelevant. If that RG58 was an antenna then yes, 18' would be a half wavelength in CB frequencies and indeed would be the length of a half wave monopole. But it isn't an antenna.

The only thing to consider is the loss per foot of the RF cable. More length = more loss, crappy coax = more loss and that directly effects your sensitivity. RG6 is about as good as it gets for "RG" and is half as lossy as RG58.

But if you are just talking with the people within a couple hundred yards it really doesn't matter. A couple dozen miles...it starts to add up.
 
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Jerry Bransford said:
Coiling the excess coax cable creates a negligible effect. Go to any large antenna 'farm' with lots of antennas like at an air traffic control site and virtually all of the antennas up on the poles have several feet of excess coiled up coax cable looped off at the top. Yes coiling a wire creates an inductor but coiling a short amount of RG58 in a Jeep is not going to have a significant effect. Not to mention the center conducted is surrounded by a braided shield that is grounded at both ends.
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Still an effect that is just as easily avoided by shortening the coax.
 
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Extra loops of coax on towers are service loops. Cables rarely fail in the middle. Service loops exist so you can lop off the end of a cable and reterminate.

Little extra in a vehicle might let you pull that radio out and look at the back while still connected.

Another good tip on this forum...remove the glass fuse and replace it with a mini...less spares to carry.

-Mac
 
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