Topband: Ground screen advantages

[Herbert Schoenbohm]

Several inquires were sent to me on where to obtain "expanded copper
mesh" which  when used properly is said to reduce E plane losses in the
vicinity of a vertical marconi type radiators.

S.C.M.C. Inc. in Charlotte, N.C. (800-438-6040) sells a high quality
expanded copper mesh sheet (8' x 24') for $249 each.  Four would be
needed for a first class symmetrical system.  They are ups ship able as
they are shipped rolled rolled up. Some years ago a BC antenna guru
wrote a paper about a field strength  test he conducted over average
soil wherein a station used both an expanded copper mesh ground screen
and 250 1/4 wave radials.  With a fixed reference field strength
measurement at a mile in 8 directions, the radials were removed one at a
time.  the author reported that no significant loss in FS was noted
until 20 radials were left.  At this point the remaining radials were
rolled up and the ground screen remained with only a 20% loss in signal
(less than 2 db).  His theory explained that most of the big losses
occur in the near field and in some cases buying up property to run lots
of radials may not be cost effective.  The problems with AM BC stations
of course are the filing requirements and the ability to maintain
certain required  FSmeasurmeents at 1 mile.  With directional systems
these requirements are even more demanding.  Yet there are probably
numerous Am stations that have ground screens and have lost radials over
the years that haven't noticed the difference on the air. (Radials
disappear quickly in some areas, especially in PR-VI where copper wire
is sold for scrap and/or used for making durable ocean fish traps. That
is perhaps why some stations have resorted to barbed wire radials as an
alternative.)

There may be some point where a copper mesh under you antenna may make
more sense than running hookup wire through the neighbors back yard
before a contest.

S.C.M. also sells copper straps 2" or 3" in 50 foot lengths for only
$49.00.  If you are concerned about ohmic loses or need some special
lightning protection at the ATU or in the shack, this is the way to go.
It is better than #2 and you can put it under the carpet in the ham
shack.

Good luck,


Herb (KV4FZ)


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