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Author Topic: Motorhome Antennas  (Read 1710 times)

Posts: 12

« on: May 26, 2010, 01:49:52 AM »

Antenna installations on Motorhomes have been very well covered on this forum, but most of the RVs seem to have fibre glass shells. My recently bought MH, a Compass Avantgard 180’s shell is constructed from three-layer laminated sheets of insulation board; aluminium; and a plastic surface sheet, over a timber frame.
At the moment I have a dual-band 2M/70cm antenna mounted on an aluminium roof bar, with four aluminium radials on the plate that joins the antenna base to the bar.
I have thought long & hard about drilling holes in the roof, but decided against it because,
A:   It would invalidate the warranty.
B:   There’s always the chance that it would leak.
C:  I’m not sure that I would be able to get a good connection to the aluminium in the shell, due to the plastic surface sheet.

I have been considering mounting a large aluminium sheet either across the roof bars, or glued to the roof, then making brackets to fit the sheet for mounting antennas.
The aluminium sheet should make a good ground-plane for VHF/UHF antennas. I want to operate 6M; 4M; 2M; & 70cm. The sheet would be isolated electrically from the rest of the vehicle.
If I glued two 8ft X 4ft aluminium sheets side by side & bonded together, on to the roof, I imagine that they would have considerable capacitive coupling to the aluminium sheets in the body shell?   That should have VHF/UHF operations pretty much covered, but what about HF?
I have a Screwdriver antenna, and also an SG-230 auto-coupler/whip antenna combo available.
Every guide ever written about mobile HF says to bond every bit of metal together. I’m concerned about bonding the aluminium sheets in the shell to the steel chassis of the vehicle in case it encourages corrosion of the aluminium?

A lot of questions, I know, but what do the experts think?

Best regards,   Stewart  GM0GTU

Posts: 10248


« Reply #1 on: May 26, 2010, 07:15:51 AM »

Peter, K5HAB, drive a mobile home with similar construction. He mounted a plate to the top of the MH, for his VHF antennas. I don't have photos of the actual plate, but it's about 30 inches square, and has 4 antennas mounted on it. It's about as good as you're going to get in this case.

As for the HF antenna. Peter tried to use an SG235 to load the top rail. That's just didn't work for a variety of reasons. In his case, he had a mount made to fit into the front bumper. While not ideal, there just isn't any other place to mount one.

Photos of his motor home are in the Photo Gallery on my web site. Look under OTR & RV.

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