CB Radio antenna

I would give up on the fiberglass mounting, compared to metal, it will never work to as well as a metal.

Here is what I have used on my trucks. yes you can use this without damaging paint. There are 2 different ones (both found on same link), depending on what your antenna needs to mount to.

I would put this on front hood, forward enough that antenna does not hit overhang of camper. I have used them for years for Amateur radio, but they also work for CB radio

http://www.firestik.com/Tech_Docs/Cab-over.htm

http://www.firestik.com/Tech_Docs.htm

If you use two cb antennas, they use each other as their ground plane.

BradW wrote:

If you use two cb antennas, they use each other as their ground plane.

Not unless one is grounded.

If both are powered, they use each other as a director......which may or not be effective if there is no good ground.

A lot of truckers use an antenna bolted to their wide mount side mirrors.

Seems like a lot of work for an all but dead technology?

I have used CBs for 40 years and they have never been grounded.
bumpy

I used half a mirror arm mount bolted to about 3"x6 plate, clamping the roof rack.

Could not tell you why it works but it does. Electrically the rack is connected to aluminum frame so it is grounded. However I use small magnetic antenna so its only grounding thru the magnetic field. Not optimum but functions.
As far as ground 'plane' do not know whats its using. I assume its the height that compensates for otherwise poor mounting. Using everything underneath as the plane.

Most mounts the shielding sheath of coax also carries ground which is connected to base-typically mounted and its grounded.

It sounds like people are confusing "grounding" like you do with an electric circuit for personal safety with antenna groundplanes. Two completely different things.
The groundplane for an antenna is more of a reflective surface that changes the antenna's radiation pattern. A metal car body serves as an antenna's groundplane. Full size half-wave antennas don't need groundplanes but on CB frequencies they are 9 feet long.
The groundplane changes the radiation pattern from somewhat spherical (and upward) to a lower, more useful pattern (down on the ground where the other cars are).
Twin antennas like you see on big-trucks are there for two reasons... mostly these days just so they look "right" but the original reason we because they affect each other and change the radiation pattern to be stronger fore-and-aft and weaker to the sides. The idea was that was better for talking up and down the freeway.
I'm simplifying a lot here but that's some of the nuts and bolts of it.

Oh, also an antenna will tend to have a stronger pattern in the direction toward the bulk of the groundplane. If you mount an antenna at the extreme rear of a car, it will be strongest forward.

How about this one. Here is a top down view of an antenna radiation pattern when there is just 1 antenna. this first picture shows you how if you can't mount the antenna direct in center of the mass, the shape of the car body affects the pattern.


Now by co-phasing 2 antenna on side of vehicle, the pattern changes as shown below.


Also an antenna is a length of wire (no need to show the math).
in CB frequencies this length is too tall for most applications so they build the antenna with a coil of wire so it still has long wire length, but is shorted physically by the coil

An antenna as a straight wire transmits from the center of that wire.
Now add a coil to the antenna and you change where the electrical center of the wire is on the physical antenna.



Here is what I like about the designs like fire stick uses.
the whole antenna is wound, but the coil is at the top, this raises your physical transmission location to the center of the wire. While it may not raise it much, it raises it enough to get the antennas electrical center above the affects of steel car parts.


in an earlier post I talked about ground plane, I could have used the word
Counterpoise instead.

We have been using the Firestick that does not require grounding for over a year now with great results. I highly recommend it for the RV. Chuck