That is a myth.....it has so little effect in regards to the wavelength that it isn't even much of a consideration. The co phasing works fine if the distance between the antennas is as close to 9' as possible but it isn't critical. I guess you would have to better define "work properly". Though, my twin Wilsons were matched individually they give outstanding performance as a pair but I do concede that a properly set up single does have noticably better omni directional performance. I'm not sure that there is a big truck out there that has co phased antenna spacing that actually measures 9' since that is usually past the generally accepted max legal width of 8.5'.

From the Firestik website:

"Spacing of the antennas in a dual antenna installation will have an affect on the radiation pattern of the antennas. Technically, spacing between the antennas should be nine feet (2.7m) to have the most balanced pattern. If that distance cannot be achieved, that alone should not discourage you from using co-phased antennas as you will still receive most of the benefits of a dual antenna set-up. However, spacing less than five feet (1.5m) may require some special tuning skills in order to achieve satisfactory SWR readings."

 

They'll work best with at least 9 feet between them, but mine work just fine.

I have more front and rear signal than side to side, but that's what you want on the road anyway.
Side to side is still fine, just not "perfect".

phox

 

I have dual firesticks on the mirrors of my truck (only one is hooked up currently as the coax got shredded by the door) Once i get them both hooked up and working , how do i tune them?

 

Firesticks usually have a threaded adjustment under the plastic cap on top.

 

I was assuming that you have an SWR meter and knew how to use it... if not you will need an swr meter and a short section of cable. You connect the meter inline between the cb and the antenna cable. Switch it to channel 20 and key it up and modulate the radio a little bit. Adjust the antennas up or down until you get the lowest ratio possible.

 

Adding an amp shouldn't increase your standing wave ratio. The wilson is a great antenna but the best antenna for 11 meters that you can acutally use mobile is a 102" steel whip. You can trim the steel whip or file it down to adjust the SWR as desired. Think of the directional stuff like this. If you place an antenna on the back right bumper. You will have more "gain" towards the right front of the vehicle. If you place it in the center it will be more omni-directional. Get the best antenna (you have a good one) and a decent radio. Then hook up a variable modulator and feed a 16 pill Davemade. Make sure you have an alternator (or alternators) that can handle your amp. draw. Also don't skimp on the coax. I always cut off the mfg coax and buy the high dollar stuff and waterproof it. Good luck and 73.

 

I have no idea what you just said.

 

Here are 2 shots of my set-up. I am also running a Wilson Firestick. The right antenna is my am/fm, the left one is my cb.

Showing the way I have it mounted:

 

The right way to do it is to remove one antenna, and replace it with a 50 ohm dummy load. Tune the other antenna. Then swap the dummy load to the one you just tuned, and do the other one. Here's a cheap dummy load that will do the job.

 

Great idea ! For those of you not familiar with electronical stuff a dummy load simulates a perfect antenna. A great troubleshooting tool as well.

 

I sure am glad JR posted that link.

All this talk of Dummy Loads.....




I was trying to figure out how this would help me tune my CB radio.


Self-Edited to eliminate any possibility of perceived impropriety

 

Hey this is a family site......


>see my edit above

 

I don't have an SWR meter , don't know what it is , or how to use it, how much does one of these gadgets cost?

 

http://www.radioshack.com/product/in...entPage=search

I think mine was $15 or so about 20 years ago.


phox

 

As previously stated a dummy load would be the proper way to do it if you wanted to invest in a dummy load and an SWR meter. The average user doesn't want to spend more on tuning gadgets than they did on the radio. I have an old oil filled dummy load someplace. Your best bet would be to find someone in your area that has the gagdets and pay them a little bit to help you.