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Unread 10-11-2013, 08:04 PM   #1
Bmel17
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CB coax and antenna question

I'm looking at installing a CB, more than likely going with a uniden pro505. I am looking at using a firestik II 2ft antenna mounted on the rear pass side tail light like the terraflex mount and using the 9ft firestik coaxial.

I want to be able to use this on the road as well as the trail, but also to be able to park it in my garage still.

Any reasons why this is good/bad?

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Unread 10-11-2013, 08:22 PM   #2
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Many fit a 3ft firestick back there. Two feet antennas are more challenging to tune. Make very, very small adjustments between reading SWR.

Firestick tech docs have lots of helpful info.
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Unread 10-11-2013, 10:48 PM   #3
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you're right, a 3 ft one will fit just fine using the bracket I'm getting.

just went and measured from where the bracket will be sitting.

Any thoughts on the coax? I have seen arguments in favor of both. I'm just trying to see if anyone has any real world experience
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Unread 10-12-2013, 04:09 AM   #4
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I used the firestick coax with the firering connector. It worked. I currently use a mini 8.
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Unread 10-12-2013, 10:34 AM   #5
Jerry Bransford
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I've had (and currently run) a 2' Firestick FS-2 antenna on two different TJs and it tunes up as readily as any of the longer antennas I have installed or tuned for others many times. I've never had any trouble whatsoever getting it tuned properly, which is good since my TJ is tall enough so a 3' antenna wouldn't fit under my garage door when mounted at tail light height.

You also asked about the type of coax cable to use... do you mean the type of coax or the type of connector? RG-58 is a good choice of cable (no need for anything heavier for the short distance used on a TJ) & between types of connectors, I feel the PL-259 male & SO-239 female connectors are more rugged and less likely to cause problems than Firestick's Firering would be.

I doubt 9' of cable will be enough. While you don't need 18' to get the antenna properly tuned, as some guides erroneously indicate is needed, that's the length I'd go for if you're buying it already put together with connectors on it.
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Unread 10-14-2013, 09:19 PM   #6
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Quote:
Originally Posted by Jerry Bransford View Post
..

I doubt 9' of cable will be enough. While you don't need 18' to get the antenna properly tuned, as some guides erroneously indicate is needed, that's the length I'd go for if you're buying it already put together with connectors on it.
Depends; if you're going to make a choke by coiling some of the cable, or use a ferrite core.
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Unread 10-15-2013, 08:11 AM   #7
Jerry Bransford
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Originally Posted by TheHeretic View Post
Depends; if you're going to make a choke by coiling some of the cable, or use a ferrite core.
Understanding what you're referring to better than you may suspect (my background is EE & 2-way communications), what are you getting at? Such issues aren't a big enough issue with a CB to try to make into something they're not.
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Unread 10-15-2013, 09:10 AM   #8
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Well I ordered everything and it's all on the way. Now I need to get a "trucker speak" dictionary

I ended up getting the 18ft length cable Jerry. I'll cut the excess off. Thanks for the help guys
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Unread 10-15-2013, 02:52 PM   #9
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I'd leave the small amount of excess cable length there, it will probably come in handy later when/if your cb or antenna ever changes location... as mine have several times over the years. That short amount of excess cable won't hurt anything.
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Unread 10-15-2013, 05:11 PM   #10
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Just don't coil the excess wire. Either run it to take up the excess or zip tie it into a skein not a coil.
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Unread 10-16-2013, 08:56 AM   #11
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All the hysteria about "just don't coil the excess wire" really blows my mind. To me, it's much ado about nothing where the types of radios we install into our Jeeps are concerned.

Go coil up your excess CB's excess coax cable & see what happens... nothing. The SWR won't change & the power output won't change. Yes I know all about inductive & capacitance reactance, RF chokes, etc., know their formulas by heart, & can design circuits that make use of such characteristics. However, in practice, it doesn't make a significant or usable difference with the frequencies and antennas we use on our Jeeps.

For example, take a close-up look at antenna farms put together by the FAA, government agencies, & military. It is standard practice, as written by their engineers. to make several coils of extra coax cable & secure it to the antenna mast for future use. I know, I used to install & take care of HF/VHF/UHF antenna farm systems and their transmitter/receiver systems. If coiling of coax cable made the kind of difference on those types of antennas to be significant, then the specs we installed them by wouldn't have been written to include the coils being attached to the antenna support masts. Which were later inspected to make sure they were installed per the specs in the manuals.

If our CBs & 2m ham radios wouldn't work well with excess coil having been coiled up into loose coils, there'd be a whole bunch of us having problems. And a loose coil at those frequencies doesn't have sufficent choke characteristics to be significant.

Not to mention there are a whole bunch of antenna systems throughout the world what can't possibly be working since they commonly coil up extra coax cable & secure it to the antenna mast. Yes there are some instances where coiling the antenna coax cable could cause a signifcant change but not on our CB or 2m mobile antennas. To me, it's a whole bunch of 'the sky is falling' type of concern where our Jeep antennas are concerned.
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Unread 10-16-2013, 11:21 AM   #12
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Quote:
Originally Posted by Jerry Bransford View Post
All the hysteria about "just don't coil the excess wire" really blows my mind. To me, it's much ado about nothing where the types of radios we install into our Jeeps are concerned.

Go coil up your excess CB's excess coax cable & see what happens... nothing. The SWR won't change & the power output won't change. Yes I know all about inductive & capacitance reactance, RF chokes, etc., know their formulas by heart, & can design circuits that make use of such characteristics. However, in practice, it doesn't make a significant or usable difference with the frequencies and antennas we use on our Jeeps.

For example, take a close-up look at antenna farms put together by the FAA, government agencies, & military. It is standard practice, as written by their engineers. to make several coils of extra coax cable & secure it to the antenna mast for future use. I know, I used to install & take care of HF/VHF/UHF antenna farm systems and their transmitter/receiver systems. If coiling of coax cable made the kind of difference on those types of antennas to be significant, then the specs we installed them by wouldn't have been written to include the coils being attached to the antenna support masts. Which were later inspected to make sure they were installed per the specs in the manuals.

If our CBs & 2m ham radios wouldn't work well with excess coil having been coiled up into loose coils, there'd be a whole bunch of us having problems. And a loose coil at those frequencies doesn't have sufficent choke characteristics to be significant.

Not to mention there are a whole bunch of antenna systems throughout the world what can't possibly be working since they commonly coil up extra coax cable & secure it to the antenna mast. Yes there are some instances where coiling the antenna coax cable could cause a signifcant change but not on our CB or 2m mobile antennas. To me, it's a whole bunch of 'the sky is falling' type of concern where our Jeep antennas are concerned.
I know what you're saying Jerry, and I respect your opinion, however. As you know the point of an RF choke is to divorce the feed-line from the radiator. I I do not want my feed-line to act as a radiator, considering how close that cable runs to myself and my passenger. The effects of RF energy on a living organism is not fully understood. Sure, CB is only 4 watts, but err on the side of caution. My HAM on the other hand is pumping 50 watts, and if I connect the RF amp, 200 Watts. That is well into Safety Code 6 territory.
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Unread 10-16-2013, 01:46 PM   #13
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So on the one hand, some are warning against coiling the excess cable because it acts as a choke. Yet on the other hand, others are advising that a choke should be installed to isolate the feedline from the antenna.

A properly tuned antenna should not need an additional choke on its feedline to prevent it from radiating.
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Unread 10-16-2013, 07:46 PM   #14
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Quote:
Originally Posted by Jerry Bransford View Post
So on the one hand, some are warning against coiling the excess cable because it acts as a choke. Yet on the other hand, others are advising that a choke should be installed to isolate the feedline from the antenna.

A properly tuned antenna should not need an additional choke on its feedline to prevent it from radiating.
I think you're looking at this in a perfect setup. Jerry, SWR changes AS THE VEHICE IS IN MOTION. You are never going to get a properly tuned antenna on a moving vehicle, the best you can do is compromise. Get as good as you can get it. Those saying not to create a choke are just repeating what was heard from some incompetent person. As a licensed HAM, I always create a choke as it's: a) good idea, b) rarely is it not required, c) and last but not least, just about every book on Antenna theory, recommends a choke to divorce the feed-line from the system. This is to reduce the risk of harmful RF coming back into the shack. Both my VHF and HF antenna's use chokes. Anyone that says a choke is not a good idea, really has no idea what they are talking about. If you want to see someone that knows nothing about antenna theory, just look to see if they put a spring on the antenna. Incredibly bad idea. You just made your SWR get much worse.
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Unread 10-20-2013, 10:43 AM   #15
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so I understand if I wire the cb to the battery it have much cleaner sound than if I wire it to be switched on/off with the Jeep. How much difference does it make with the noise?
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