Will my whip antenna work ?

[63air]

My Globetrotter has all the wiring in place for the installation of a CB radio but one was never installed. It also had the whip antenna installed ,which I really like the looks of. I plan to install an Intellipower then I can use the CB wiring to power a really nice car stereo system. Will the old CB antenna work for the new stereo or do I have to go to another antenna? Sure be neat if there is a way to make it work.

[Ag&Au]

Originally Posted by 63air

My Globetrotter has all the wiring in place for the installation of a CB radio but one was never installed. It also had the whip antenna installed ,which I really like the looks of. I plan to install an Intellipower then I can use the CB wiring to power a really nice car stereo system. Will the old CB antenna work for the new stereo or do I have to go to another antenna? Sure be neat if there is a way to make it work.

It won't work as well as an antenna designed for FM radio, but it will probably work well enough to satisfy you. I would try it before I decided to install another antenna.
Regards,
Ken

[Phoenix]

Most large whip antennas for CBs are 102", if I recall correctly. The length is 1/4 wave length. If the antenna has a ball mount base and big spring, with a removable whip, you might be able to replace the whip with the proper length for FM. However, it will probably be really short compared to the big whip, and might look kind of silly. Radio shack or an amateur radio operator might be able to help you with determining the proper whip length, if you end up cutting one to size. Also, you might be able to get a wound, loaded whip, but that would be even shorter.

[Tom Nugler]

Some quick calculations found the wavelength for the FM band to be about 3 meters.
Technically, the optimum antenna length should be a full, 1/2 or ¼ wavelength. This makes the standard 102-inch whip a bit too short for a full wave.
Practically speaking it shouldn’t make any real difference as long as there are good connections between the radio, coax, mount, ground to the body and antenna.
Wire it up and see if you like the balance between performance and the look of the vintage whip.

Tom.

[Phoenix]

Tom's comment brings up something that I forgot from my old electronics training: Random length wires are OK for receiving (although, not as good as a tuned, directional antenna). And the reason CB antennas are a specific length, is because they are also used to transmit. The tuning reduces standing wave interference, which reduces effective output power.

I agree; you should check to see if the existing antenna works good enough for your use. One note, though; the coax impedance differs for CB and FM (which is close to the old broadcast TV frequencies). CB is 51 ohm and TV/FM is 75 ohm. If the signal is too weak, you might want to try replacing the CB coax with TV coax before you do anything more with the antenna.

By the way, the old CB whips with no loading coil were 102" for 1/4 wave, and the metal parts of the auto or trailer reflected the other 1/4 wave. If you had a 102" fiberglass whip with a big bulge in the middle, this was probably a 1/2 wave, center loaded antenna. Full wave antennas weren't really practical for mobile applications, due to the size required to simulate a full wave. Other shorter lengths were usually base loaded or center loaded and could be as short as about 18-24".

I hope most of the above is relatively accurate, because this was buried somewhere back in the old gray matter, from the '70s. You might want to talk to an amateur radio operator who would be more knowledgeable. It sounds like Tom might have more info, too.

[Finch]

this might be off topic, but there are acouple CB retailers that sell kits that allow you to use one antenna for the CB and AM/FM radio. tho it is a fibergalls antenna (3 foot) seem to work very well in the auto market

[Safari64]

Will the old whip antenna work for AM signals? How do I do that?

[Finch]

Originally Posted by Safari64

Will the old whip antenna work for AM signals? How do I do that?

with one of these, Firestik AR1A - CB Antenna to AM/FM Splitter - Electronics Superstore www.WalcottCB.com

this will alow you to use one antenna for your CB and/or am/fm radio

[63air]

Sounds like it just might work. Wallcot CB is near us so I will probably head over there and talk to them.

[Finch]

let us know how it goes, i have a feeling there are others interested as well

[overlander64]

The 102" whip antenna on my '64 Overlander International has proven its value in three different applications over the years that I have known the coach. Originally, the antenna was connected to a 12-volt AM radio mounted in the front streetside roof locker. The second owner upgraded to an early 1980s AM/FM 8-track Stereo radio for which it performed as well as any of the contemporary antennas on that era's automobiles. Since the 8-track tape player had ceased to function by the time I acquired the coach in 1995, I chose to install a 40-channel CB radio so that I could receive the daily announcements and news at the WBCCI International Rallys -- works beautifully for that purpose as well. My observation indicates that the cable terminal end was changed each time to match the needs of the electronic device to which it was connected.

Kevin