Wayne,
I know what you are saying and agree. In very simple terms, if you
can load it, it will radiate. That was a position that a writer with the
nom de plume of Kurt N Sterba too in a book he wrote. By the physical
law of conservation of energy, it all has to go somewhere. And, that
could be heat or radiation. In his book he claims to have loaded a
shopping cart and talked to people.
Yes, you can do these things as long as you make good connections
and the tuners can handle it. All of the discussion is how to pick a
length that the tuner will accept. Once there, physics takes over. And
just to prove my point, and yours, I just worked the CQ 160 CW contest.
My antenna was a vertical 20 meter dipole center fed with open wire. My
radio is a K3s. I worked across this country, Canada, and some DX with
this 33' wire antenna that by all rights should have been over 200'. I
would have done better, but my local power company added another
handicap, line noise. Bottom line: Throw some wire up and see if it can
be loaded. If yes, go for it.
73,
Barry
K3NDM
------ Original Message ------
From: "Wayne Burdick" <[email protected]>
To: "Tom McCulloch" <[email protected]>
Cc: "Elecraft Reflector" <[email protected]>;
"[email protected]" <[email protected]>
Sent: 1/29/2017 12:40:58 PM
Subject: [Elecraft] The "Kinda Random Antenna" (was: Random wire lengths
for antennas)
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
On Jan 29, 2017, at 7:55 AM, Tom McCulloch <[email protected]> wrote:
I guess we need an alternate definition of "random" ;-)
Tom
wb2qdg
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[email protected]
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [email protected]
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[email protected]
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [email protected]
