CB Radio Antenna type

[Dan n Lisa Lund]

Good evening ladies and gents

I searched the forums and couldn't find an answer to this question. The CB antenna on our coach is mounted about midway down the coach just aft of the refrigerator. Since the body skin of the coach is mostly fiberglass did Beaver use a NGP (no ground plane) antenna or do they have the antenna using the metallic coach structure for the ground plane? I would like to get the CB working but was not sure about the antenna type. I am sure there must be a radio tech out there that has this answer. Any info would be greatly appreciated.

Thanks,
Dan

[Steve Huber Co-Admin]

Dan,
Not sure as to what SMC did, but you should be able to verify the type by hooking an ohm-meter between the base of the antenna and chassis gnd. If it reads high resistance you've got a no ground plane unit. I would think they found an Al "stud" to anchor the unit to but you never know.
If the antenna is a Firestick antenna, the factory here in Phoenix may be very helpful. After I called them and described my issues (poor SWR readings)with my previous Beaver they had me bring the coach to the factory and we tried different antennas until we got the best reading. Cost was minimal.
Steve

[Dan n Lisa Lund]

Good idea on checking for a ground to the chassis. I will give it a try.

Thanks

[Edward Buker]

Dan,

I would not worry too much about SWR with this CB arrangement. It is made to provide short range communication as you know and the antenna is mounted high which is good.

I would want to know three things, with the antenna mast removed (hopefully a connector with a ground and center lead at the antenna mount) does the center lead have continuity to the center lead in the antenna PL259 connector that goes into the CB at the dash. Also does the ground lead have continuity between the antenna mount and the CB connector. Are the two (ground and center lead) isolated from each other. This is easy to measure with an ohmmeter. Measure for isolation, should not have continuity between the center pin and ground. Then use a piece of wire to short the ground to the center lead at one end (antenna or cb), use the other end to measure for low ohms between the center and ground lead at the plug. This tells you that the wiring and connectors are as they should be. I would inspect the antenna for cracks, breaks and if it looks OK remount it. All of the connectors at the antenna end should be moisture free. If this test is fine then I would not worry about the ground plane or swr, it should work fine and there is not a whole lot you can do at these low frequencies to improve things swr wise anyway.

Later Ed

[Steve Huber Co-Admin]

Dan,
Couple of follow-up comments.
SWR mainly affects your radio's ability to transmit. So, if your main use to to listen to the truckers, etc. a poor SWR will not have an impact. If, however you want to use the radio to talk, a poor SWR will have a fairly noticeable effect on your ability to transmit over any distance. Since CB'ers are in moving vehicles, rapidly changing distances can play a big role.
Another way you may be able to verify if you have a NGP antenna is to look at the antenna cable at the junction box. NGP antennas require a special coax. If the coax is thicker for the first ~ 3-9", it's a NGP cable. (At least that was what the cable on my Cobra looked like).
Steve