oh man, that's funny. and yes you did say you'd come up with something better. but i still gotta give it to you for your first idea too. that was pretty good.

BTW, i like how you stick to your word

 

Actually when you have 2 antennas it creates what is known as a phased array. Optimally the antennas should be a certain distance apart and they need to have a certain phase relationship from the energy being fed to them but there are no cut and dried rules here.

The difference in length of the coax feeding the antennas determines the phase relationship. This can be calculated by first multiplying the velocity factor of the cable which is always less than 1 by the wavelength of the frequency you're using. For CB at 27 mhz 1 wavelength is generaly 36' or 11 meters. 1/2 wave is 18' and 1/4 wave is 9'. If the coax has a velocity factor of .85 then 1/2 wave of coax will be 18 X .85 = 15.3'. I don't remember what the velocity factor of RG58/u is and I'm to lazy to look it up.

By using an equal length of coax to each antenna they would be considered to be in-phase and if they were very close together (inches) they would tend to act as one antenna with very little directionality.

I'll assume that truckers would want better transmission ahead and behind their truck to talk to other trucks so the coax is probably set for 1/2 wavelength phasing. In this case the closer the antennas the more they would tend to cancel each other out but that energy has to go somewhere and if it isn't radiated it will go back down the coax and show up as a high SWR.

If you had 1/2 wave of difference in the coax feeding the antennas and they were 1/2 wavelength apart then the energy would add in the direction of a line at right angles to a line drawn through the 2 antennas. The energy would be canceled in a line with the antennas.

With the same separation and equal length of coax feeding the energy would be canceled best at right angles to the line through the antennas and would add in line with the antennas.

Sooooooo.... Optimally they should be 18 feet apart and in phase or 1/2 wave out of phase depending on which direction you want your energy to go.

If you could mount your antennas 18 feet apart on the trailer in line with the road and phase them with equal lengths of coax it would radiate best down the road in front and in back.

Or you could just mount a 6 element beam and a rotor on that sucker.

 

Good info. Anybody else playing with the skip tonight? I'm at Fort Knox, and just got a 5x5 check from a guy at Fort Campbell. About 140 miles.

Running bareback with the little radio, on a single 9 Foot whip.

Ed

 

Been there, done that, gonna' do it again real soon in the next VHF/UHF/microwave contest.
Rotatable 5element 2M VHF beam and an 19" mil-surplus X-band radar dish for the 10Ghz SSB microwave transceiver all mounted on a 316SS barstock mast threaded into the gooseneck ball hole in my PU bed..
The beam stands highway speeds really well, but the dish doesn't. Working on a pneumatic raise/lower system to get the dish below the roof line for travelling at speed.

Get stares? Do ya THINK?

I love the expressions from kids... They are awed...

K.

 

I like the 9' whip on the car. When you have it tied down in front and somebody is tailgating, just let it loose. It's puts a little dent in their hood and they back off.

Edwin

 

You are an EVIL man