Hi Bob,
Since nobody else seems interested in responding seriously to your
question....
SteppIR and ZeroFive are correct: depending on the size of the roof (and
for most average sized houses, it's fine) the metal roof will be God's gift to
radial systems.
Remember, the whole idea of radials, particularly in ground-mounted
applications, is to emulate as closely as possible a continuous sheet of
metal, which your roof is.
You do need to connect the roof to the radial attachment point of the
antenna.
Some things to watch for, however: RFI is one. Have an intermittent or
slightly corroded connection at a seam and you're in for RFI.
Lightning is another consideration. One, I think, to be aware of, but not to
dismiss the idea of a roof antenna. Making sure you provide a solid,
low-impedance path to ground, will be key. There are lightning experts
here who can advise better than I.
73, kelly
ve4xt
> From: Robert Bogash <rbogash@centurytel.net>
> Date: 2006/08/16 Wed PM 05:20:30 CDT
> To: towertalk@contesting.com
> Subject: [TowerTalk] Elevated Vertical with No Radials on Metal Roof
>
> I have an interesting QTH, and am mulling over a new elevated HF
> vertical. I have studied all the usual suspects on eHam etc and poured
> over the Champion report on vertical antenna performance.
> Unfortunately, it is now a little dated and Steve, K7LXC says no
> follow-on work has been done. And, I have corresponded with a few of
> the manufacturers.
>
> My QTH can be seen here: http://www.rbogash.com/ham.html
>
> I have a large expanse of saltwater extending 180 degrees in front of my
> house, pointing at all the good places, which would make a vertical
> really shine. And, I have a large 24 gage steel roof, which I think
> would make a great ground plane, and, er, obviate the need for a tuned
> radial system. I've already experimented a bit by putting a 20 meter
> Hamstick in a mag mount on my roof. This antenna outperforms all my
> other 20m antennas on rx and tx by a wide margin, and it's not even
> tuned very well (more work ahead to fix that.). I figured my house roof
> was way better than a car roof. I've worked the world with this little
> baby, and figure if a little bit of antenna is good, then a BIG antenna
> is even better!
>
> I'm looking mostly at 10-15-20m, altho 40 would be OK too. My existing
> G5RV and Long-wire do fine for me on 40 and 75 now, so I'm not
looking
> for a kick there at this time.
>
> I've gotten emails from SteppIR and ZeroFive saying the metal roof
would
> beat any radial system hands down. Any comments on my roof antenna
with
> no radials? Should the antenna radial connection point be bonded to
the
> roof? And, does anyone have any experience with the ZeroFive
> Multi-band 43 ft monster (tuner required.)?
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|