On Thursday, November 6, 2014 3:15:23 PM UTC-5, wrote:
I'm planning on building a 10 meter ground plane antenna out of PVC pipe and #12 wire radials drooping about 40 degrees. This will be mounted on my roof on a tripod and mast, with the radials also serving as guy wires. The ARRL antenna book mentions that a ground plane antenna should be mounted at least one half wavelength above "ground". I know that this sounds like a stupid question but I have to ask: for this example do I consider the roof, which is more than 5 meters above ground level as "ground" or do I need to be at least 5 meters above the roof. I would like to secure the radials, (guy wires) to my roof, but with the antenna at 5 meters high my droop angle will be off and then I can't guarantee a 50 ohm match. The house is wood frame, no foil backed insulation and a non metallic roof. Thanks for any advice. Lenny

To build this antenna I plan on using an SO239 inside a length of 1.50 or 2 inch PVC pipe, and bringing the 4 radials, which are cut to 1.05 wavelength,(as per the ARRL Antenna book) out through four drilled holes up toward the top of it. Then I'll use an adapter to convert to half inch pipe, cap the top end of the half inch and run the # 12 wire radiator straight up into that. I'll bring my 213 up inside the pipe, connect to the SO 239 and seal the whole thing up with silicone. The thing will be mounted on a tripod and the radials will have insulators on them so that they'll double as guy wires as well.

I built another ground plane years ago and it's still up there and in use using this method for my business band radio. That unit operates in the 40 MHZ band and I recall that I came up with a very good SWR on that one. I'm nowhere near half wavelength above the roof with that one either but I had to ask.

So now I have to ask another stupid question. I'm stripping old Romex for the wire and I mentioned this to a local friend the other day. He asked me if I was using bare wire for the radiator. I said that I didn't think that it mattered. He assured me that it did. I would think that either in free space or inside a plastic pipe that it wouldn't matter. Am I correct or is he? Lenny