Rick N6RK wrote :
It would be interesting
to see if really short beverages exhibit these nulls. Otherwise,
useful as they may be, they are acting a degenerate low dipoles,
but still beat listening on the transmit antenna.
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I too wondered what the pattern of the beverage looked like as its length
was reduced so I did a simple model using EZNEC demo for a terminated 1.8
MHZ beverage (500 ohm termination) mounted 5 feet above ground using a ground
conductivity of 0.005 S/m, for beverage lengths of 150 feet to 550 feet in
increments of 50 feet, and I created a simple website where you can view
the progression of the patterns (3D pattern looking down at the pattern
from above).
The website URL where you can view the patterns I created is
_https://sites.google.com/site/beverageantenna/_
(https://sites.google.com/site/beverageantenna/) and if you click on a
pattern it will expand in size for easier
viewing.
I am by no means an expert on using EZNEC, but I believe the plotted
patterns do provide insight into the behavior of the beverage at different
lengths. It looks to me like lengths of 300 feet or more start to become very
interesting (using the parameters I used) but this does not mean shorter
lengths are not useful (similar to what Rick said), but will let everyone draw
their own conclusion from the plots.
Note : the 500 ohm termination provided a reasonably flat SWR versus
frequency regardless of the lengths I used when analyzed from 1 to 7 MHZ.
73's
Don (wd8dsb)
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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