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Old 10-18-2017, 08:47 PM   #1
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CB radio antenea

I have a fiberglass highroof, my van has a plastic hood...

I'm kinda new to CB, but have done the youtube research. I know that some types of antennas need a ground plane like a steel roof or steel hood.

Where do I mount and and what type of antenna do I use?

Edit: My interest in CB is two-fold. A) communicating with members of a group while out on a 4x4 trail (mostly for my Samurai) B) as a back up 'get help' system while on solo trips
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Old 10-18-2017, 09:03 PM   #2
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Quote:
Originally Posted by TomsBeast View Post
I have a fiberglass highroof, my van has a plastic hood...

I'm kinda new to CB, but have done the youtube research. I know that some types of antennas need a ground plane like a steel roof or steel hood.

Where do I mount and and what type of antenna do I use?
Google "Marine CB Antenna" and you will find some that do not require a ground plane. Made for fiberglass boats....
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Old 10-18-2017, 09:35 PM   #3
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I use a Firestik CB antenna on my Bronco. On the page below, on the left-hand side, there's a "No-Ground Plane", CB Antenna Kit:

CATALOG Main Page (Frame Setup)

My Bronco has a soft top, and a fiberglass hood, so there's a distinct lack of a ground plane, and it works just fine.


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Old 10-18-2017, 10:20 PM   #4
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Interesting read here re: Ground Plane. Seems like we still have sufficient metal to have a ground plane vs a boat. A non Ground Plane antenna may create some issues???

"ground plane for a CB radio antenna is the metal surface required below the antenna. In mobile applications, the vehicle body/frame acts as the ground plane (reflective unit). The metal surface enables the signal generated when transmitting to reflect off the surface and travel into the atmosphere"

https://www.wearecb.com/cb-antenna-ground-plane.html

I have just purchased a Cobra CB and Firestik Firefly 4 ft. antenna so this was timely , the 4 ft get s the top of the antenna up above the pop top and rack by by a little bit.
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Old 10-18-2017, 10:45 PM   #5
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Can you mount a ground plane up on the rack?

Quote:
Originally Posted by 1der View Post
I have just purchased a Cobra CB...
Which model did you buy Ray?
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Old 10-18-2017, 11:43 PM   #6
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Can you mount a ground plane up on the rack?
Good question;

or would the expanded metal and 1-1/2" crossbars at the rear of my custom rack act as a ground plane?

I'm very interested in how well your system works when you get it up and running, Ray.

As Broncohauler points out, Firestik offers a $60 non-ground plane (NGP) antenna and molded side mount that sounds good. I read a little more tonight, Jeepers with soft tops like NGP antennas. It looks as though I could mount it on the side of the fiberglass highroof, as though it were a fiberglass capped class C motorhome. The big rig guys must have the same dilemma with those big fiberglass tops.

The reason I ask is because from what I've read, it seems a guy can put together a poorly though out POS of a system and have only a few miles of coverage (if that), or 'figure it out' and get 5-6 miles, or more line of sight.
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Old 10-19-2017, 12:08 AM   #7
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I simply bent up a piece of flat bar steel to go from one of the fender bolts, through the seam between the hood and the fender, and then horizontal with a hole for the antenna in the horizontal part. It doesn't stick above the roof, but I still get a few miles range, and since I never talk to anyone I'm not traveling closely with, it serves my purpose just fine. For additional range, I always have my 2M / 440 ham rig. Its antenna uses a similar mount on the other side of the hood.
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Old 10-19-2017, 12:15 AM   #8
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Back in the 70's I was always told a lot had to do with location of the antenna in respect to the shape of the ground plane. Marine antennas work well on water but may not perform as good as one that's properly placed on a metal roof especially in wooded hill type terrain. My radio covers a few bands and have an antenna with a load to make it work OK over the frequency range spread. My roof rack is aluminum but placing it in the middle wasn't an option. But that was a long time ago It's in front of the penthouse.
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Old 10-19-2017, 12:19 AM   #9
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I think the expanded metal would definitely provide the ground plane IF it is grounded to the rest of the body/frame. That may be easily accomplished, or not.

That being said, and I considered it would be easy to add a plate or grate on my roof rack but decided against I did not want three plus more feet of anything above my roof line. I am already pushing 101" to the pop top surface and another 9" for the rack so just over 9 feet.

My plan is to mount the antenna on one of the swing arms or on the box towards the middle of the back of the van. This is why I went with the 4 ft version so I can get the top of the antenna about 8 inches above the upper part of the rack and the 12" of fiberglass top will essentially be transparent. Who knows, I will get it installed and finely tuned and then I will see what it really does, lol! Stand by, good buddy
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Old 10-19-2017, 09:46 AM   #10
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A couple of general rules with vertical antennas.

1. Radiation comes from the current in the antenna and that is at the base of 1/4 wave length vertical antennas. So it doesn't help much to have the top peeking over the top of your rig. You will still have distortion in the radiation pattern.

2. If you use something like a plate or wire or other thing to create a ground plane the shape and length is important. You should have at least 8 feet in some direction from the base of the antenna for CB frequencies.

3. Some antennas that don't require a ground plane use the coax cover as the ground plane and that makes the length of the wire to the antenna critical. Others create a 1/2 wave length poll which moves the highest radiation part up the antenna and they usually work better.

4. You need a way to measure SWR. If you have a 1/1 SWR then you are in good shape. It means your power is going someplace and not back into your radio.
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