Coaxial Cable Antenna

Thread Starter

biferi

Joined Apr 14, 2017
390
I Live in the USA and I was going to get a CB Radio in my House.

I will have a Coaxial Jack for a Coaxial Cable to go to an Antenna.

So the one End of the Coaxial Cable will go to my CB Radio and the other End of the Coaxial Cable I was going to take apart.

I know I can have the Center Pin go to the Right Antenna Lead and the Outer Shield can go to the Left Antenna Lead.

I only want my Antenna to have the Right Lead so what would I do with the Outer Shield?

This will be going in a Window I can not have it Out Doors.
 

SamR

Joined Mar 19, 2019
5,039
The coax should have a PL-259 coax connector on each end. This simply screws into the coax jack on the radio and on the other end screws into the antenna jack. Unless the antenna comes with coax already built into it and has a PL-259 on the end of it already, then a S0-239 adaptor is used to screw the cables together. The center of the coax is the signal, the outer sheath is the ground connection. To use the center conductor of the coax as an antenna is problematic to say the least. It should be exposed (unshielded so remove the coax shield) for at least a quarter-wave of the 11meter frequency you wish to use. Even then it won't fit in a window and would still need some fine tuning to work properly. An automobile mag-mount antenna might fit on a windowsill because it uses a wound base and sometimes a wound wire on top of a fiberglass rod so that it is a 5/8 wavelength but coiled in order to be a very compact antenna. Either way it will not work very well. The key to CB antenna's is elevation above ground with a good ground plane under the antenna.
 
Last edited:

bassbindevil

Joined Jan 23, 2014
826
Check out some books on diy antennas at worldradiohistory. CB on 11 meters is similar to ham radio 10 meters, or there are CB specific books with antenna plans. It would help to have an antenna tuner if your antenna is a compromise. Back in the CB heyday, I remember articles on making an antenna that looked like a short flagpole that could mount on a window frame or apartment balcony, or using a Slinky toy as a collapsible antenna that could be dropped from a balcony and retracted using a fishing reel and line.
 

Ya’akov

Joined Jan 27, 2019
9,117
If this is 75Ω coax, of the sort used for cable TV, you can’t use it directly. You will have to provide a matching device of some kind, like a balun or a stub to match the 75Ω feedline to the 50Ω radio.

The antenna will also have a characteristic impedance that must be matched to the feedline as well. The feedpoint of the antenna is one way to influence the impedance. It is lowest when the two legs of the antenna are equal and increases when it is moved towards the ends.

It is almost certainly best that you find and follow plans for a covert CB antenna instead of randomly cobbling together something. You should also get an SWR meter, it will be the cheapest and easiest way to check that you have gotten the antenna right.
 

Externet

Joined Nov 29, 2005
2,216
There is several ways to bypass prohibitions to install antennas.

- A less-than-1mm-diametre copper wire dipole suspended with fishing nylon can be invisible. Keep the coax section indoors.

- There is a law that nobody can prohibit to install a flag pole. Use it. ;)

- Any wire tossed/hanging can perform well with an antenna tuner.
 

MisterBill2

Joined Jan 23, 2018
18,442
A CB radio antenna will need to be well matched and resonant only if the goal is to communicate with others not nearby, within shouting distance. So a single wire will work adequately to communicate a few hundred feet. If a greater distance is desired then the second half of the dipole antenna is required, and the antenna must be the correct length to resonate. Consider that the maximum power output of the transmitter must not exceed 3.5 watts, and most radios deliver closer to 3 watts to assure that they are legal, an adequate antenna is required. The arrangement described by the IT IS NOT an adequate antenna. It will sort of work to some extent, but the results will not be nearly as satisfactory as doing it correctly.
 
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