Cb antennas

[TexasCowboy]

Does anyone know of a good dual antenna set up for a truck

 

[Vortec Lover]

Does anyone know of a good dual antenna set up for a truck

doesn't exist

if both are hooked up they interfere with eachother, if you run duals (like me) than one is just a dummy.

And you want a longer cb whip because theoretically you need about 2/3 above the highest point of the vehicle for better reception. Some think 4' is overkill, I think it is about perfect, cosmetically and functionally.

just make sure you get a quality whip, good coax and a halfway decent radio. You can make a cheap set up sound good, you just need to make sure the antennae and coax are good quality

 

[1997chevydriver]

When you run duals, your talking range is directional instead of a even radius around your vehicle. With both antennas hooked up your range is farther front to back than it is left to right. I have both of mine hooked up.

 

[Vortec Lover]

I mounted my whips to my toolbox, ran the coax between the cab and bed, over my exhaust heat plates, into the engine compartment and through my firewall.

 

[NacIK]

When you run duals, your talking range is directional instead of a even radius around your vehicle. With both antennas hooked up your range is farther front to back than it is left to right. I have both of mine hooked up.

Actually it is the opposite for a pickup. With at pickup the range will be further side to side because the radio-waves are attracted to the other antenna.

The reason this works so well for tractor trailers is because they are so long. I can't remember the exact reason why, but something about the metal in the truck makes the signals run stronger from front to back, which is desirable for truckers because they want to talk to others on the same road most of the time.

I found this on one of the CB forums when I was researching speech processors.

 

[great white]

http://www.gmt400.com/forum/showthr...im-looking-for&p=404387&viewfull=1#post404387

Coles notes for your question:

Dual antenna's a pretty much pointless except for looks. More in the link above.

Truck tool boxes are horrible places. You get too much reflected wave from the vertical surface of the cab and this drives your swr up. SWR can kill your transceiver. Truck boxes are also not well grounded. Note that is RF grounded, which is a very different beast from DC grounding. If you must use a truck tool box, get at least two 1" wide copper braids and make a good RF ground on either end of the tool box and the truck bed. Scrape both down to clean bare metal at each end of the braid. Then do the same for at least the two front corners of your bed to the frame if not all 4 corners. This is the difference between getting out a mile or two and getting out 5-10 miles. Theoretically, CB is no longer effective past about 12 miles, although hitting skip can get you thousands. Skip listening is done on almost any CB, skip talking usually requires the power of SSb radios although you can on the regular 40 channels if conditions are just right.

If you really want dual antenna's, install one with regular rg8 50 ohm coax and leave the other one unhooked. A single will perform better than a dual on a pickup. Dual antenna's on a pickup are too close together to "co-phase" and be directional. Even semi's are too close together to co-phase. Co-phasing is what makes you antenna directional. Co phasing also requires 75 ohm coax of identical length to a splitter then 50 ohm coax to the radio OR identical length 75 ohm coax all the way to the radio. Dual antennas are also a major PITA to get your SWR set on as each antenna has to be identical lengths. As in less than 1 MM difference, even then it very difficult to get SWR down to acceptable levels.

Really, just install one live antenna and one non live if you must have the dual antenna look....cheaper and easier and it will talk better than trying to cophase them.

Cheers

 

[Vortec Lover]

you are a great assett to this forum greatwhite-

 

[great white]

Actually it is the opposite for a pickup. With at pickup the range will be further side to side because the radio-waves are attracted to the other antenna.

The reason this works so well for tractor trailers is because they are so long. I can't remember the exact reason why, but something about the metal in the truck makes the signals run stronger from front to back, which is desirable for truckers because they want to talk to others on the same road most of the time.

I found this on one of the CB forums when I was researching speech processors.

The signal in a mobile application is, for lack of a better word, "drawn" to the area where the most metal is present:

You must be registered for see images attach

a little known fact about rigs is that most run with one hooked up and one dummy. When they split one on over head signs and whatnot, they switch the coax to the good antenna.

Rigs are also front talkers, not rear although there is still signal rear. The trailer is not rf bonded well enough to the tractor to be part of the "dipole" and just becomes a big vertical surface that blocks the signal rearward at best and reflects the signal back to the antenna and raising SWR at worst. The foot is slipping and bumping around (as well as greased within an inch of it's life) and the air/electrical lines do nothing of significance in RF. Most rigs are wondering what's in front of them so the loss to the sides is kind of immaterial and when they're talking rear is usually not very far. Couple miles at best, maybe a bit more with a strong signal from a "footwarmer". This is also fairly irrelevant and they only really care about what's up around the corner or when the loading dock wants them to pull in. Footwarmers usually just make them louder at best, and splatter over adjacent bands at worst.

Most new tractors are a nightmare to set up well because vast portions of them are fiberglass which completely frigs up good signal propagation. There are many many fixes and workaround guys are struggling with on the newer rigs. May very well be the last nail in the coffin for the biggest users of cb these days...

It's all kind of moot anyways, cb is effected by so many factors that on one day you may talk 20 miles, the next day you may get 2 miles and the day after you might skip 150 miles. Sunspot cycles change everything again with skip. It all makes it nearly impossible to compare the performance of one antenna to two antennas unless you have them both ready to go with a coax swap at the radio (or a switch box) and someone sitting a known distance away at N,S,E and W evaluating your signal. Even then, each of the 4 listeners would have to have identical setups in order for it to be a useful comparison.

Cb is just for fun brothers. Do it as inexpensively as you can, as simply as you can and go have fun modulating!

 

[West Mi Mudder]

you are a great assett to this forum greatwhite-

x2. No matter what the subject is, Great White is there to give you his knowledge.

 

[great white]

x2. No matter what the subject is, Great White is there to give you his knowledge.

Oh, that doesn't mean I'm 100% right 100% of the time.

I just do my best to be as accurate as possible and try not to step on my d!k too much....