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Old 06-28-2018, 8:51 PM
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Default Ground Plane bars For A Fiberglass Roof

Our daughter just bought a van conversion camper that has a fiberglass roof. She wants to install a CB radio with a mag mount antenna. She is willing to install a 6" X 6" metal plate for the magnet mount; however, she needs a ground plain. Would it be feasible to weld four, 1" flat bars to the metal plate to give her a workable ground plane on a fiberglass roof? If so, how long would the flat bars need to be?
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Old 06-28-2018, 9:05 PM
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Well, ideally, 1/4 wavelength, which isn't going to happen, so generally you make them as long as you can.

If you can get to the underside of the roof, you can use adhesive backed foil tape, often used in HVAC systems (not duct/duck tape…)

Or, run 3 or 4 small gauge wire down to the body in each corner.

Personally, I'd be concerned on a couple of aspects…
-Mounting a steel plate to the roof to hold the magnetic mount antenna is either going to require some strong adhesives, or drilling holes. I'd suggest if hole drilling is in her future, just go straight for a thick mount NMO and put a decent NMO base antenna up there. It'll likely seal better.
-Steel is also going to rust and leave streaks, so you will need to protect it really well.
-She still needs to get the cable inside to the radio….

Or just find a half wave type antenna and skip the ground plane.
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Old 06-29-2018, 4:57 AM
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Quote:
Originally Posted by mmckenna View Post
Well, ideally, 1/4 wavelength, which isn't going to happen, so generally you make them as long as you can.

If you can get to the underside of the roof, you can use adhesive backed foil tape, often used in HVAC systems (not duct/duck tape…)

Or, run 3 or 4 small gauge wire down to the body in each corner.

Personally, I'd be concerned on a couple of aspects…
-Mounting a steel plate to the roof to hold the magnetic mount antenna is either going to require some strong adhesives, or drilling holes. I'd suggest if hole drilling is in her future, just go straight for a thick mount NMO and put a decent NMO base antenna up there. It'll likely seal better.
-Steel is also going to rust and leave streaks, so you will need to protect it really well.
-She still needs to get the cable inside to the radio….

Or just find a half wave type antenna and skip the ground plane.
Thank you Mmckenna, you are always ready to help. It is very much appreciated.
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Old 06-29-2018, 6:37 AM
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The HVAC wide aluminum tape has worked great for me, especially for VHF/UHF antennas but for CB its best to get as much ground plane as you can under the antenna due to the much longer wavelength.

If the antenna will be a permanent part of the camper and your not concerned with looks you can cover the roof with a sheet of thin aluminum or galvanized sheet metal as big as you can get. 4 X 8ft would be great and even a 4 X 4ft square would be better than a few strips of aluminum tape. You can pop rivet the sheet metal or hardware cloth to the roof and its easy to waterproof with a few dabs of silicone goo where the rivets go through the fiberglass.

I've also seen the entire underside of a fiberglass camper shell covered in aluminum window screen then given a coat of surfboard resin to keep it in place and turning the camper shell upside down while doing the resin made that possible.
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Old 06-29-2018, 7:13 AM
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Quote:
Originally Posted by SnowWalker View Post
Our daughter just bought a van conversion camper that has a fiberglass roof. need to be?

Not sure if I'd want to be sitting underneath that antenna if she's going to be running any power.
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Old 06-29-2018, 8:53 AM
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Quote:
Originally Posted by mmckenna View Post
I'd suggest if hole drilling is in her future, just go straight for a thick mount NMO and put a decent NMO base antenna up there.
Great advice.

Re-engineering the roof to accommodate a mag-mount seems silly.
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Old 06-29-2018, 9:26 AM
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If that van conversion has a metal hood, the mag mount possibly could be placed there for the grip and ground plane. I place a mag mount 56-inch Wilson 500 on the metal hood of my Jeep Wrangler that has a fiberglass roof. I only use it for trips that I need radio communications, and remove the radio and antenna when not needed. It works and communicates quite well.

If there is no metal hood, I'd drill a hole and install a no-ground-plane antenna system on the fiberglass roof. This is a common solution for fiberglass RVs. The performance will be reduced a bit, but it should do well for several miles of highway communications. It is those several miles that are the most valuable for using the CB to get or give information about local highway problems or when traveling with a caravan.
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