ZL3IX I think by accident had a fence with a break in it. My not
working Beverage was 4'up over a continuous welded wire fence. Then
some NEC2 modeling of a 600' Beverage 6' above a continuous 3 wire
(wires at 2,3, & 4') barb wire fence, showed poor F/B. Mine was worse
over the welded 6"x 6" mesh fence (it's been a while but I recall none).
Some NEC2 modeling (just re-confirmed with NEC4) showed that breaking
the fence into three 200 ft insulated sections, for the length of the
Beverage solved the problem. More fence continuing off the ends didn't
matter. I didn't build it before I moved.
Having seen a good selection of barb wire fences, many probably don't
have electrical continuity, including many of mine. Since there seems
to be wide agreement and sound engineering reasons that Beverages don't
work over high conductivity ground, so I trust that modeling.
Regarding NEC not working near the the ground, the EZNEC manual claims
NEC2 is ok within a few wire diameters. Neither NEC2 or 4 will work
really close to or with any part of the wire in the ground plane.
N6LF did some very nice work confirming how NEC4 was accurate for buried
wires with some very good experimental data. He includes some comments
about ground variability.
https://rudys.typepad.com/files/qexjul-aug-2016-bog.pdf
Re MikeK's adventure with loading inductor permeability made variable
with DC current bias of the B-H curve, I think it's an interesting idea.
I suspected he was trying to do that and hope he finds a way to make it
work.
Grant KZ1W
On 8/24/2019 10:52 AM, Mike Waters wrote:
As long as the fence is pointed in the right direction. :-)
www.w0btu.com/Beverage_antennas.html#Misc_Beverage_antenna_notes
On this page, there are some links to ZL3IX (?) experiences with his
Beverages mounted at different heights above metal fences.
73, Mike
www.w0btu.com
On Sat, Aug 24, 2019, 12:47 PM Chuck Dietz <w5prchuck@gmail.com> wrote:
And, by the way, K5GN and W5KU report that their Beverage above a barbed
wire fence is the BEST Beverage at their place.
Chuck W5PR
On Sat, Aug 24, 2019 at 12:41 PM Chuck Dietz <w5prchuck@gmail.com> wrote:
I seem to remember someone saying the modelling programs are unreliable
when a wire is close to the ground. Also, there is really no way to model
the properties of "ground." It can vary in just a few feet and the moisture
content varies from day to day. I think this is a "try it" kind of antenna.
Read other's reported results.
Chuck W5PR
On Sat, Aug 24, 2019 at 12:29 PM Mike Waters <mikewate@gmail.com> wrote:
The only way to predict the RDF and pattern is by modeling it. I don't
know
of anyone who has done this. I have a few of my .ez Beverage models in
w0btu.com/files/ as a starting point, but I don't think that I uploaded
everything there.
There are free antenna modeling programs out there. I have only ever used
EZNEC. Maybe someone can suggest something.
73, Mike
www.w0btu.com
On Sat, Aug 24, 2019, 12:05 PM Mikek <amdx@knology.net> wrote:
But what did you mean by "proper pattern"?
I should have said, the best pattern that adjusting the Inductive loads
will provide.
Yes, I understand the pattern changes with frequency. What I want to
do is
inductively load the antenna, so it will have the same pattern as if we
increased the length.
Say I have a BOG with a length that is ideal to give me the best RDF
number available at say 1.8Mhz.
Now, I move down to 1MHz, and I inductively load it, can I get that
same
RDF number?
ie. can I reduce the VF to make it act like the correct length?
What are the caveats?
Thanks, Mikek
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