Posted by
Don Wilhelm on
Sep 08, 2018; 2:13pm
URL: http://elecraft.85.s1.nabble.com/searching-for-post-by-Wayne-n6kr-about-counterpoise-tp7644921p7644928.html
Tom and all,
One of the KX2 Field Testers found that a 58 foot resonator and a 26
foot counterpoise worked well on 80 through 10 meters.
I use half those lengths for 40 through 10 meters.
No feedline, both the radiator and the counterpoise are connected
directly to a BNC to Binding Post adapter on the KX2.
The direction of the counterpoise does not make a lot of detectable
difference. Antenna modeling may show some difference, but working
quickly in the field may not allow you to set up the "perfect" situation
- use what you have available.
The KX2 internal tuner is a wide range tuner that might even be able to
match a metal window frame or the proverbial "bedsprings".
Let's face it, this is a compromise antenna that can be thrown into a
tree and give us the opportunity to make QSOs in the field. For home
station use, a proper antenna up in the air will be better.
73,
Don W3FPR
On 9/8/2018 9:50 AM, Tom McCulloch wrote:
> 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
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