I have not had the opportunity to construct a 4-square or other phased
vertical array yet, but the planning has been going on in my mind for a
long time. In particular I have pondered the question of how I would
construct the grid of the ground plane. Even though I may change the exact
configuration a number of times before I finally get to the project, the
following are my conclusions of the general concept together with the
reasoning.
When constructing a ground mounted vertical array we are always attempting
to achieve the most perfect reflector possible in the radial (ground plane)
system.
I have been involved in VHF/UHF communications for many years and the most
effective location for mounting mobile antennas is on the roof of the
vehicle, preferably in the center of the roof. In all cases it is
desireable to mount the antenna at least 1/4 WL from the edge of the roof.
If we are mounting multiple antennas for many bands (10, 6, 2, 1 1/4, 3/4
meters, etc.) they are all grouped quite closely together on the roof,
especially on a pickup truck. We attempt to keep them as far apart as
possible (to prevent possible mutual coupling) but they all share a common
ground plane.
Taking this concept to the HF and MF bands, it would stand to reason that
the more extensive and complete the ground plane can be made, the better
the performance will be. The key is to make the ground plane as
symmetrical as possible, in particular for a phased array for a single band.
This is a quick reply, is not all encompassing, and certainly contains
nothing more than my personal thoughts, observations, and conclusions.
Good luck to all, and thanks for the replies to my questions on feedline
isolation and the 205-BA.
73 de Milt, N5IA
--
FAQ on WWW: http://www.contesting.com/topband.html
Submissions: topband@contesting.com
Administrative requests: topband-REQUEST@contesting.com
Problems: owner-topband@contesting.com
|