Towertalk
[Top] [All Lists]

## [Towertalk] Dipole setback on a cliff

 To: [Towertalk] Dipole setback on a cliff richard@karlquist.com (Richard Karlquist) Tue, 16 Jul 2002 22:52:05 -0700
 ```FWIW, a couple of weeks ago I took the mobile up to the top of a mesa. It was a really great location for VHF: I could receive FM broadcast signals from 200 miles away with armchair copy on the car radio. These disappeared off the mesa. On the ham rig on 17 meters, however, it was nothing special. Even for signals in the same direction as the FM signals I was receiving. The ham antenna was a 13 foot whip (full 1/4 wave on 17 meters.) I was located 25 feet from a vertical drop of 100's of feet. Rick Karlquist N6RK richard@karlquist.com www.n6rk.com www.karlquist.com > -----Original Message----- > From: towertalk-admin@contesting.com > [mailto:towertalk-admin@contesting.com]On Behalf Of Bill Tippett > Sent: Tuesday, July 16, 2002 7:05 PM > To: W4EF@dellroy.com; towertalk@contesting.com > Subject: [Towertalk] Dipole setback on a cliff > > > W4EF wrote: > > >They have a 160 meter inverted-vee mounted on a 40' telephone pole > close to the edge of a ~500' mesa. Looking in the direction > of the 500' > dropoff, what is the effective height of this antenna? Is it 40' or > 500'? > > I'm not how YT would work for this but I think EZNEC can > handle it...even with one ground conductivity for the near earth and > another for the mesa valley (if that were a salt flat for example). > Intuitively, I would guess that the pattern would be a combination > of two patterns: > > 1. A 40' dipole for TOA's above arctan (40/X), where X is the > distance from the tower to the dropoff boundary, and > > 2. A 540' dipole for TOA's below that same angle. > > In other words, it might look like a low dipole primarily, but > could have some secondary low-angle components below the main lobe > (which radiates most of the energy straight up). > > Interesting question which EZNEC can easily handle since it > can handle two different ground heights and conductivities (but only > two). The two grounds can be either a linear boundary (the cliff > problem you described) or a radial boundary (a circular boundary > with the antenna at the center). I'll let someone else do > the model! > > 73, Bill W4ZV > _______________________________________________ > Self Supporting Towers, Wireless Weather Stations, see web > site: http://www.mscomputer.com > Call 888-333-9041 to place your order, mention you saw this > ad and take an additional 5 percent off > any weather station price. > _______________________________________________ > Towertalk mailing list > Towertalk@contesting.com > http://lists.contesting.com/mailman/listinfo/towertalk > ```
 Current Thread [Towertalk] Dipole setback on a cliff, Bill Tippett [Towertalk] Dipole setback on a cliff, Richard Karlquist <=