When I was a novice, I lived in Corpus Christi, Texas, in high conductivity
soil about 3 blocks from the Gulf of Mexico. Crystal controlled on 21.106,
I became a DXer. Every time I would hear something and not work it, I
would go out and install three more radials in the ground around my 14AVQ.
I ended up with more than 60 countries and more than 60 radials. When my
general ticket arrived, I put up a 40' Rohn push up mast with a 108" mobile
whip at the top with a loading coil at the base of the whip and four
sloping radials. I carefully tuned the coil and radial length for
resonance and adjusted the slope of the radials to lowest SWR. On 15M, the
elevated GP beat the 14AVQ ground mount every time in every direction at
every distance except 3 blocks away. A three element "Gotham" beam (
anybody ever modeled one of those historical curiosities?) at the same
height as my GP was slightly better (less than 3 db) than the GP. And that
14AVQ was probably in the best possible environment for a ground mounted
vertical (although I guess I could have been 1/4 wave from the water ala
6Y4A). In Central Texas soils where I live now, I won't even consider a
ground mounted vertical, but a would do an elevated GP if that was fit for
the space and supports available.
-----Original Message-----
From: Tom Osborne [SMTP:w7why@mail.coos.or.us]
Sent: Thursday, July 23, 1998 1:03 AM
To: TowerTalk
Subject: [TowerTalk] Antenna Comparisons
Hi All
Last week I was on an extended camping trip and thought I would
take the rig along to pass the time. I wasn't sure what type of antenna
to use, so I did some experimenting.
The first antenna was an elevated 20 meter ground plane with the
base about 10 feet in the air. It seemed to work real well as worked
some good stuff on it. Not being satisfied, I took it down and put up a
delta loop at about 30 feet. It didn't work nearly as well as the
elevated 20 meter G.P. with 4 radials. I've seen posts on the reflector
about elevated GP's but I didn't think the elevated GP would work that
much better than the delta loop. I think I'll raise the verticals I
have here and see if they work better. 73
Tom W7WHY
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|