Pat,
8 to 10 feet above the barbed wire fence would be your only chance if
you are to use the existing fence lines. I would strongly suggest
reading some (all) of the references you have been offered -
particularly those that include long term experiments.
My information has simply been gathered from the reports of others over
nearly 40 years and confirmed by the performance of the few simple
Beverages I've been fortunate enough to use at various times.
The general consensus has been not to use a "ground wire" under a
Beverage or run it along above/parallel to a conductive wire fence.
Maintain at least 45 degrees and try, if at all possible, to cross
other antennas/conductive objects at right angles.
Ideally, in your case, you might use fewer, stronger supports and
perhaps enclose them in a small 4' x 4' fenced enclosure to prevent
them from becoming the "scratching post". At 10' high, the Beverage
does not need to be as tight as a fiddle string which means you could
probably get away with a support every 100 feet or so unless you were
using extremely soft wire. Again, these are areas of experimentation
and you will need to determine if the decline in performance from the
fence justifies the effort in other areas. Note however, most Beverage
users in the US will find they want/need antennas around 45/225 degrees
(EU and VK/ZL) and 135/315 degrees (Caribbean/East Asia) while a 0/180
degree Beverage has very little use except for Central Asia over the
pole. Getting the most used "quartering" antennas will require some
solution to the "scratching post" problem in any case.
73,
... Joe, W4TV
On 2015-02-03 2:35 PM, Patrick Greenlee wrote:
Joe. Thanks for that info. Your comments and those of others make it to
start not looking good for putting a Beverage wire a couple feet above
one of my fences. I might still try maybe 8 ft above the top wire of
the fence. What do you think of that? Having the Beverage above the
fence, even at 8 ft or more above the top wire is quite attractive as:
1. The fence posts would be easier to extend than to come up with anew
just for the Beverage.
2. We are a working cattle ranch and structures have to withstand cattle
bumping them or chewing on them (They ate my Dish TV coax, a garden
hose, and the wires of a remote weather station. It would be a pain to
have to wrap PVC posts in barbed wire to be able to have them away from
an existing fence. and then they would be in the way of haying.
3, Running a Beverage on its own would require an installation with the
wire's lowest part of its catenary above the reach of the cattle and deer.
A lone T-post or PVC pipe becomes a scratching post and will get shoved
over. Our fence posts survive because they have 5 strands of 4 point
barbed wire stretched tight and secured to them. It is uncomfortable to
push on the barbed wire.
If I were to install a Beverage with its own posts then as a minimum I
would have to have a single strand of hot wire at around 24 inches above
grade. Then you have to switch the hot wire off to use the antenna
because of the once a second 10Kv+ pulses and the RF noise you get. The
herd would have to be rounded up and put elsewhere because if the hot
wire is off too long they figure it out and ignore the wire creating
more repair work to detract from Ham projects. Too much hassle.
Sad story, huh? Not really as there are tradeoffs like room to spare, no
neighbor closer than 1/4 mile, no permits for antennas or towers, no
CC&Rs, no homeowner's assoc, you can pee off the front porch and do
anything you want on the back porch, target shoot up to and over 1000
meters (or yds) and no one will complain. The down side is the
difficulty of finding help. I am one of the two hams in my zip code and
the other guy is not in good physical shape. There isn't an electronics
store better than Radio shack (a 2 on a scale of 10) within 100 miles.
Not a Ham store or store with a ham or electronic hobbyist department to
my knowledge in the state. Staples is the computer store for this area
and that is a 60 mile round trip. Best Buy is nearly a 100 mile round
trip, and those are the best we have.
Would I want to move closer to civilization. NO WAY!!!
Many thanks to those who have shared their experience, knowledge and or
opinions in response to my questions. I will find a way to experiment
with a Beverage.
Patrick NJ5G
On 2/3/2015 7:55 AM, Joe Subich, W4TV wrote:
I'm curious to know if the fence would act similar to good
conductivity dirt WRT Beverage performance.
Anecdotal reports over the years (~ 30?) of Beverage antennas over
an existing conductive wire/fence indicates that performance lags
that over moderate earth. The degradation comes from two apparent
modes: 1) the (typically larger) fence picks up noise and couples it
to the Beverage and 2) the the conductive nature of the fence upsets
the velocity factor (wave tilt) resulting in a shorter effective
length with lower signal strengths and broader patterns.
73,
... Joe, W4TV
On 2015-02-03 8:39 AM, Patrick Greenlee wrote:
Chuck, A very good point.
That is the essence of my interest in the effect of having some parallel
grounded conductors (5 strand barbed wire fence with steel posts) a
short (TBD) distance below the beverage antenna. I'm curious to know if
the fence would act similar to good conductivity dirt WRT Beverage
performance.
If not, then what if the antenna wire were mounted above 3 parallel but
horizontally spaced conductors looking for the beginnings of the effect
that would be achieved theoretically with our old friend the infinite
conductive plane over which we mount our verticals? Why 3? Because it
would be easy to put a strand of wire on either side of the top strand
of barbed wire using readily available inexpensive plastic insulating
arms made expressly for adding electric fence wire to a fence built with
T-posts. With a little more fussing I could attach 2 wires either side
of the center wire giving a better approximation of the infinite plane.
One of our experts can maybe tell me if the parallel grounded wires
need to be tied together laterally or if that would matter.
Patrick NJ5G
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