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View Full Version : Is there any advantage to running 2 antennas on a tractor trailor vs 1 antenna??????



easy2517
05-03-2013, 07:10 AM
I'm thinking of going back to 2 antennas on my Peterbilt. Has anyone seen any advantage running 2 vs 1 antenna even with power??

Thanks

onesixdoublezero
05-03-2013, 07:35 PM
Running with two antennas on a tractor trailor helps to even out the transmit pattern as transmission patterns tend to pull more to were the body mass is. Mount the antenna on the left the transmission pattern will be greater to the right, the same will happen if it is mounted on the right the pattern will be greater to the left. When two are used they give a more even transmit pattern to the front and back. If using power with a cophased antenna system keep in mind that the coax used in most kits will only hold about 1500watts P E P.

Moonchild 747
05-04-2013, 08:15 AM
Another thing to remember when adding a co-phased end fed mono-pole antenna system is ensure you use a equal amounts of 75ohm coax and try to keep the distance of the antennas close to 1/4 wave length part to keep your radiation patterns symmetrical...EZNEC is a great antenna design program to mess around with and it show you everything you would like to know about your antenna set up and design flaws. 75 ohms coax is used because the impeadance increases from approx 36 ohms of a standard 1/4 wave design to nearly 75ohms with a dual phased system...ensure you join to a good 50ohm T and run back to the radio with good 50 ohm coax. 8 ft seperation may not be possible but try to get the most separation you can...reason truckers place on mirrors instead of roof, that and it easier too...

Silverado 996
05-19-2013, 12:03 AM
http://www.cosjwt.com/index.php?a=20

peterwo2e
07-15-2013, 05:50 AM
The advantage will not be noticeable if any. Antennas are too close together. 2 antennas 2 headaches. Co phase antennas work better when a certain feet apart. A truck is not wide enough. I tried this many years ago and notice no advantage in my van.

Moonchild 747
07-21-2013, 09:58 PM
The advantage will not be noticeable if any. Antennas are too close together. 2 antennas 2 headaches. Co phase antennas work better when a certain feet apart. A truck is not wide enough. I tried this many years ago and notice no advantage in my van.

Exactly...Dual antennas should be 1/4 wave length apart to achieve the right 50 ohm match at the radio and intended directional RF pattern...But you'll see them on trucks anyway and they because putting one up on the side of your truck will pull the signal toward the opposite side of the truck...Placing two on opposite sides but closer that 1/4 wave length or 8 ft will just give you more balance with your signal, much like placing the antenna in the middle of the roof giving you omni direction.