I actually constructed 1/8 of a system of 500 radials 4 wavelengths long
on 20 meters. The 45 degree sector with the long radials was pointed
toward Europe. It was worth an extra 3 dB when using a half wave
vertical, but no advantage with a quarter wave vertical. I also
simulated systems up to 1000 radials 8 wavelengths long on a special
version of NEC. The experiments were in line with that. My QTH is
in an area of high (30 mS) soil conductivity, so the radials may
help more in other places. Complete details of the study are on
my web site <http://www.karlquist.com> .
Rick Karlquist N6RK
rick@area.com
www.karlquist.com
> From: "Clive Penna" <clive@gm3poi.prestel.co.uk>
> Subject: [TowerTalk] Ground Radial Fields
>
> HI, Does anyone have any field strength data, re the lowering
> of radiation angle in a given direction if extra radials are concentrated in
> that direction. ie taken to the extreme 60 radials covering 180deg whether
> that arrangement would have the performance of 120 radials at the mid way
> point,and the radiation angle increasing as you run out of radials. 73 Clive
> GM3POI
>
> ------------------------------
> From: "Jim Reid" <jreid@aloha.net>
>
> Hi, I believe the radial field "density" will not impact the take
> off angle. That is established several wavelengths on out
> from the antenna. The radial field is there to improve the
> efficiency of performance, that is, RF to the antenna
> set up from the rig vs. the RF energy actually radiated
> and not lost in resistive heating of the dirt below, hi.
> 73, Jim, KH7M
>
> ------------------------------
> From: Eric Gustafson <n7cl@mmsi.com>
> Subject: Re: [TowerTalk] Ground Radial Fields
>
> (compared to other directions) will be largely insignificant. To
> really do TOA lowering by improving the ground around a full size
> vertical, the ground must be improved for a great distance out (3
> to 8 wavelengths depending on your goals). The required radial
> density for 3 wavelength long radials is much higher than for 1/4
> wavelength radials. For example, a 3 wavelength radius radial
> field with a screen density at its outer edge equivalent to a 1/4
> wavelength radius field with 120 radials would require
> approximately 1260 radials.
--
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
|