This is probably NOT what you are looking for but it's about random
length antennas...it goes back to Jan 29, 2017.
hope this helps:
I'd call an ad-hoc antenna that works on multiple bands with an ATU a "Kinda-Random
Antenna" (KRA). (Apologies to linguistic purists.)
A simplified definition might be:
A. long enough to work within the maximum limits of the ATU's L-network on
the lowest band used
B. presents a reasonably low impedance on all bands used (e.g., doesn't look
like an end-fed half-wave)
ATUs have limited monotonicity and granularity, as well as stray impedances, so
in practice there is a third criteria:
C. tunable on each band used despite specific L-network idiosyncrasies
This third criteria is the hardest one to predict for a given ATU design, as
the idiosyncrasies vary with PCB layout and actual component values. They may
only impact the highest bands, or for a particular antenna, the bands on which
Q is the highest. For our ATU designs, we try to minimize strays and keep the
network monotonic by using tightly toleranced capacitors and toroidal inductors.
While a wide range of wire lengths will meet the requirements of a "KRA" in the
field, we've found from experience that something in the 25'-28' range works on all bands
from 40 meters up, and roughly twice this for 80 meters up. Since it's impossible to
predict the effect of ground losses, obstructions, deployed wire angles, etc., you may
occasionally need to add or remove wire to obtain resonance on all bands used.
73,
Wayne
N6KR
Tom
WB2QDG
K@ 1103
On 9/6/2018 11:57 PM, JEROME SODUS wrote:
Hello,
I want to re-read a post that Wayne n6kr made about a wire-antenna tossed up a
tree and the location of a counterpoise; this was relative to portable
operating a kx2 or kx3, if I recall correctly.
But my archive search has come up empty.
My recollection is he recommended placing the counterpoise in a direction
opposite to the wire-antenna.
I need to verify that recollection.
Hopefully someone has saved that post.
TIA for any help.
73 Jerry km3k
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