CB Radio Antenna Question

[cracked]

hey yall. i recently bought a cb radio for my truck but failed to aquire an antenna. instead of buying one, could i just run a line from my am/fm radio antenna to the cb radio? if not, why? if all of the same frequencies/signals are hitting each antenna and are not filtered out until you reach the actual radio, why cant i do this? the reason i am assuming you cant is because when people have a cb radio, they also have a cb antenna. whats the difference?

and if i can do this, great!

drew

[caddmannq]

The ideal length (or the "electrical length" in the case of a coil-loaded antenna") is different. A CB antenna is best at 103" or so. An FM antenna is best at about 33" or so. An AM antenna is in between. (Lengths quoted are approximate, and I'm not gonna look them up for you )

Now that doesn't mean that it won't work at all...
just that it won't work at it's best.

If you don't know about antennas, there are a lot of little things to consider, including the type and size, and configuration of vehicle you're going to mount it on, the typical usage you're going to encounter, etc.

I'd go talk to a CB specialist if you can.

[nunyadam]

Plus with most cb antenas you will need to set the standing wave.
(think fine tuning) for optimal performance.

magnetic mount units work but the standing wave will change depending on where you place it on the vehicle.

I would recommend FireStick CB antennas. I don't personally have a CB, but a lot of my wheeling buddies do and that's all they use.

[pickel]

Get you some dual antenas. They always worked the best for me...in a pickup truck.

[cracked]

i drive a bronco II and i want to get one of those antennas that bolt onto the rear bumber on one side. is there a specific term for these to know b4 i go shopping?

drew

[caddmannq]

Dual antennas (mirror mount) work well, if you're broadcasting straight ahead or behind of the truck. Great on a straight highway, & so a lot of truckers use them. You can switch one off to improve reception "sideways" to the truck.

A big "ground plane" helps too. A 103" whip up in the middle of a large metal camper roof can be a very high-performance setup in the mountains.

But running around town, you gotta tie it down so you dont break things A whip on the bumper isn't as good, as the major ground plane (metal roof of the truck) is not at the base of the antenna.

A coil-loaded job is a lot shorter & you wont need to tie it down, but it looks like a longer whip to the CB because of the coil in it. It works well up on the middle of the roof too.

Coils suffer some loss that a whip doesn't, however; though there may be some high-tech jobs nowadays that are actually better. I don't know...
I've been outa the CB business for many years.

[caddmannq]

Oh, yeah...all that changes if you've got a fiberglass roof

Glass isn't a good ground plane.

I've got a nice 60" whip sitting in my garage if you're interested.

What you need is a mobile model with high dB gain. Avoid center-load or top-load coils as they generally fail to deliver a good SWR match at the edges of the CD frequency spectrum.

I recommend a quality bottom-load coil antenna, especially if you are only pushing 4 watts. Avoid cheap antennas like the plague, as you get exactly what you pay for, a piece of junk metal.

I have used the K40 with great success, plus can honestly recommend anything from the upper tier of Wilson, such as the W-5000.

And yes, they make a ohms matching transformer that allows you to use your FM antenna, but would hope you are interested in transmitting more than half a mile.

Cadd is correct about mounting. If the antenna is at the corner of the vehicle, then it will have a tendency to concentrate the signal in one direction being in the direction of the longest ground plane. The bumper will work, but you will get back directivity problems with a cheap, low-gain antenna.

Check out this site for antenna ideas:

http://www.copper.com