cb problem

i got a used 18 wx stii i was installing it per the instructions and when i hit the transmit button i get a really lot buzz on my speakers, also my fog light switch lights up. all of my conncetions are good, and i went and double checked all my grounds(when i unplug the ground from my fog switch, i still get the noise). Is this an internal problem in the cb its self? or am i a ****ing *******

*update*


moved the coax away from my amp power cord and that got rid of the buzz, then i put my swr meter in line and it got rid of the short, am i getting too much power from my antenna?

what is your standing wave. im assuming you have a bad ground at the antenna. ill bet you have a SWR abouv 3:1. what coax and antenna do you have out of curiosity. here is my mount

I'd hate to catch that ant. on something! It'd rip the roof off!

i have since notched the tail light, added a spring and run the coax behind the tail light

i have something just like the last guy on the tail light i bought the mount of some guy from i forget his name but it hasnt done me wrong yet

i know this thread is kinda old but this needs to be known. if that mount is bolted to the plastic tail light you arent getting any ground (seeing how plastic is an isulator.) an antenna system needs to be grounded to the body of the vehicle. the metal of the body is half the antenna system. its called a ground plane. the RF travels along the ground plane. im sure if WheelinJR could chime in on this he could explain it better than i. seein how he has his ticket. and probably has a better understanding of this sort.

the antenna system needs the ground to achieve the proper Ohm load of 50 Ohms. without that ground it basicly becomes an open curcit. the SWR (Standing Wave Ratio) is a measure of how effitiantly your antenna, coax, and radio work together. the radio wants to see 50 Ohms, the coax is and wants to give the radio 50 Ohms. the antenna is adjustable (all of them) some easier than others. all mobile antennas for CB, also refered to as 11 meter (physical wavelenght). are 108", or 1/4 wavelenth. a full wave beeing 36 feet. for the antenna to resonate properly it needs to be 1/2, 5/8, 3/4, or full wave. the groundplane of the vehicle is what gives you the other 1/4 wave to be a 1/2 wave. anyway i confused myself, again. fire away with the questions.

juniorXJ said:

i know this thread is kinda old but this needs to be known. if that mount is bolted to the plastic tail light you arent getting any ground (seeing how plastic is an isulator.) an antenna system needs to be grounded to the body of the vehicle. the metal of the body is half the antenna system. its called a ground plane. the RF travels along the ground plane. im sure if WheelinJR could chime in on this he could explain it better than i. seein how he has his ticket. and probably has a better understanding of this sort.

the antenna system needs the ground to achieve the proper Ohm load of 50 Ohms. without that ground it basicly becomes an open curcit. the SWR (Standing Wave Ratio) is a measure of how effitiantly your antenna, coax, and radio work together. the radio wants to see 50 Ohms, the coax is and wants to give the radio 50 Ohms. the antenna is adjustable (all of them) some easier than others. all mobile antennas for CB, also refered to as 11 meter (physical wavelenght). are 108", or 1/4 wavelenth. a full wave beeing 36 feet. for the antenna to resonate properly it needs to be 1/2, 5/8, 3/4, or full wave. the groundplane of the vehicle is what gives you the other 1/4 wave to be a 1/2 wave. anyway i confused myself, again. fire away with the questions.

Click to expand...

You'll still get a ground through the screw - but it won't be as effective as a direct ground (also, he's using the OEM "oxided" screw, switching to a galvanised/Cd-plated screw would also be an improvement.)

You also don't "get power" from your antenna - it's a passive device. However, the description of SWR tuning is spot-on - if it's not set up correctly, you transmit and receive will both suck mightily. Most production CB antennas need to be trimmed a bit for the specific application - which is where the SWR meter comes into play (the closer you can get to a radiating element with 1/4, 1/2, or full wavelength "length" (sometimes, 1/8-wave will serve - but only for HF/LF radio.) In this case, the average wavelength of the CB radio signal is 11 metres. Half of that is 5.5 metres, and one-fourth of that is 2.25 metres (~36.2 feet, ~18.1 feet, and ~9 feet respectively. If you could get it to work, then 4.5 feet, or 1/8-wave, could also happen.)

Note that I said "effective radiating length" - this isn't an absolute measurement of the radiating element. The ground plane has a good deal to do with effective radiating length - so once your antenna is set up, you may as well replace it if you're going to move it to another vehicle, or even to a drastically different location on the same vehicle (if you want it to stay tuned well. Roof to roof would be a minimal change, but could be affected by the change in vehicle mass, roofline surface area, ...) That's why antennae are tuned using SWR as a standard - since you'll need a different length of radiating element for a roof-mount as for a side-mount, as for a hood-mount (akin to a BFM/BAM antenna.)

The antenna has rather more to do with clean radiation than the transmitter itself - which is why antenna tuning is so important. You can make a cheap radio sound much better when the antenna is set up properly, and an expensive radio can sound a good deal cheaper if the antenna is off...

woohoo someone else that knows what thay are talking about. my mobil is going to get real complicated real soon as im getting ready to set up a reflector element and later down the road 2 directors. but thats a hole nuther can of worms, we wont get into that here.

Transmitting antenna MUST be tuned to the radio and vehicle. It must be mounted to a metal surface. The radio needs a good ground. Moving the antenna (even on the same vehicle) requires the SWR be rechecked. A bad enough SWR can wreck the output transisters of the radio. Always check the SWR at channels 1 and 40. Not all antennas can maintain a decent match all the way.

Most folks set the SWR for best match at channel 20 and then check the match at 1 and 40. If your antenna can't maintain a good enough match at one end or the other, you can set it for a good match for the channels you will use and just don't use the channels where the match is too far off. Or, better yet, get a better antenna.

The antenna uses the body to help radiate the signal. Therefore, the higher you can mount it the better it will work and the more metal you have around it the better it will work. Mounted at the rear of the roof will throw a better signal forward. Mounted at the front of the hood throws a better signal rearward. Mounting the antenna on the right rear corner of the vehicle throws the strongest signal off the left front of the vehicle. Good if you use your radio mostly on the road. Think about that as you decide where to mount it.

Best all around location is the middle of the roof (side to side), center (front to back of the whole vehicle, not just the roof) of the vehicle.

CB antennas are 1/4wave (9') radiators. If its physically shorter, you will find a coil on it somewhere. If you run the coax into the vehicle through a door opening, be sure it will not get crushed. Also, don't coil up any excess coax nice and neat. This creates an inductor (wire coil) and inductance will screw up your SWR. Just bundle the extra coax randomly (it'll look pretty messy) and stuff it out of the way somewhere.