Second Generation Nissan Xterra Forums banner

1 - 16 of 16 Posts

·
on line
Joined
·
8,599 Posts
Discussion Starter #1 (Edited)
My antenna cable got torn open by the rear hatch opening and closing. So I decided to revise my CB setup. I had some free stuff laying around in my garage so I figured it would be better than buying all new stuff. My setup now is dual center load antennas on the front bumper. I decided to go this route cause I had a proper dual antenna coax laying around as well as the antennas.

It's not the best setup for the trails and will most likely swap them out with shorty whips. It's not the most appealing also. Probably will only use these antenna on long road trips. Also I'm aware the scepticism about running dual or single antennas. Also the reason for mounting them on the bumper, was I'm tryin to limit the clearance issues. I can still fit in parking garages and in my garage.

But I've found a good resource for info and figured I would share.
http://www.rightchannelradios.com/cb-radio-resources.html

Post up any good sites that u find!!
I've been talkin to a friend that gave me the stuff and he's giving me a few tips that I haven't seen on the net. He said that looping excess antenna coax will decrease power to the antenna.
Posted via Mobile Device
 

·
on line
Joined
·
8,599 Posts
Discussion Starter #6
I haven't really gotten much range testing on it yet. Haven't even tuned them yet. I put them on this mornin. Center load is suppose to be the best for a long metal antenna.
Fiberglass top load is next best.
You should go through ur current setup and make sure its grounded, tuned, and ur coax isn't damaged.
Posted via Mobile Device
 

·
on line
Joined
·
1,739 Posts
Co-phased antennas should be 8-9 feet apart for best performance.

Antennas should be mounted as high as possible for best performance.

For trail use you're on your own as trees will tear high mounted antennas down.
 

·
on line
Joined
·
8,599 Posts
Discussion Starter #9
See, I've read a few things on the net saying dual antennas need 8-9' apart. But also read where a guy hooked up dual antennas to some fancy thingamajig and took readings at different distances apart.
Here
http://www.cosjwt.com/index.php?a=20

Close together they have a even zone. The further they are apart, it becomes more directional. Which is preferred by semis.
Posted via Mobile Device
 

·
Registered
Joined
·
1,049 Posts

·
on line
Joined
·
8,599 Posts
Discussion Starter #11
Yea I know duals arent optimal or that's what some people say. But it seems controversial on it being not as good as people make it out to be. I've seen people say it's not good but also seen people say its just fine with them mounted close. Also like I said I had the stuff just layin around.
Thanks for the links. I'll have to read through them.
Posted via Mobile Device
 

·
Registered
Joined
·
1,011 Posts
So by "dual antenna coax", I assume you mean 75 Ohm coaxial cable, or just that you have a coax splitter? Is the length of coax to each antenna exactly the same? Dual antennas are harder to tune; have you done it before? Your setup is likely to be extremely directional (and not necessarily perpendicular to the antennas like you might expect.)

A little theory for the curious: Two antennas CAN reinforce the radiated signal in a given direction, IF they are mounted approximately 1/2 wavelength from each other. For CB radio (11 meter band), this equates to about 204", which is wider than any vehicle on the highway. For that reason alone, the best setup for an antenna on a vehicle is the center of the roof, grounded to the body to make the roof a ground plane for the antenna. Semi trucks have good reason for mounting 2 antennas on the cab (because the bulk of the truck/trailer is in between, blocking the signal from the other side).

The other problem you may have is that your antenna loading coils are well below the roofline. I predict your signal strength and reception quality will be OK out the front of the X, but noticeably worse when communicating with stations that are behind you. That type of antenna is really better off on your roof, or at least mounted so the loading coil is above the roofline. I would put you at the back of the trail convoy for better comms with the group :D
 

·
on line
Joined
·
8,599 Posts
Discussion Starter #13 (Edited)
The cable is one piece, I did not use a splitter, and it's same length since it's one cable technically.
Like I said about not wanting it on the roof. I had a antenna, roof lights, roof basket, hilift, spare, and all that fun stuff up there before. I didn't like it up there. I don't want to have to fold or disconnect it to get I to my garage or parking garages in the city. So bumper mount was what I wanted. Yea not optimal of a set up but optimal for what I want. The antennas were free and probably some of the better antennas out there, so that would be better than having shorter whips or so, on the front bumper.

I've read plenty articles sayin duals aren't good because they are directional. But also have read that they only become directional the further they are apart. When they are with in 4-5' they basically have the pattern of a single antenna but slightly oblong. It doesn't become extremely directional until they seperate further and have more of a 8 pattern to it.

Definitely not gonna have that great of range behind me but obviously I will still be able to talk to someone with in a 1/4 mile.

Here's some really good info. It would be nice if it was orginized a little better.
http://www.firestik.com/Tech_Docs/63Things.htm
That was one that Rocknhd had in that link.
Posted via Mobile Device
 

·
Registered
Joined
·
1,011 Posts
What you said about the antenna pattern is basically correct, the oblong (elliptical) pattern is what I was referring to- the short axis of the ellipse can represent an actual decrease in range over a circular (single antenna) dispersal pattern. As for the cable, I'm having trouble understanding how you connected 2 antennas with 1 cable. Are they connected in series? If so, only one of the antennas is really doing anything (the one that is closer to the radio along the wire.)

The only way I know of to connect 2 antennas to a single radio is to use a Y splitter and equal lengths of coax. If the coax lengths aren't equal the signal gets biased toward the closer antenna- just like the series discussion above.
 

·
on line
Joined
·
8,599 Posts
Discussion Starter #15 (Edited)
It is one complete cable. Not 2 individual cables. It has one connector that goes to radio and comes out a little then splits to two cables with a connector on each end. Being one complete cable made for dual antennas. But it's not a splitter connector with 2 individual cable connected.
Posted via Mobile Device
 
1 - 16 of 16 Posts
Top