Bill,
There are many factors that could impact on his system
effectiveness. The one that most comes to mind is height above ground.
160 meters can be a real problem. If it is a horizontal, the average ham
antenna height of 35-50 feet is very, very low electrically. Two things
would happen here. First, a lot of energy is being lost to ground, and
second, the radiated signal will be at high angle. Remember, a quarter
wave on 160 meters is on the order of 135 feet which is the point where
you get maximum radiation straight up. At lower heights, gains upward
goes down and doesn't fill in toward the horizon. The means electrically
low antennas are not effective.
The other area that comes to mind is the feed system itself. Not
mentioned is whether open wire is being used. I would guess that the
system SWR may be very high meaning losses on coax should be much
greater than a 1 db. And, some tuners are not low loss when operated at
their extremes.
I get away with what I do ONLY because my 20 meter vertical antenna
is less effected by being low, I feed it with ladder line which has low
loss even at absurdly high SWRs, and the tuner I use is designed to be
used with antennas that are no where near optimum.
From what I did this weekend, I could surmise that my 33' radiator
was radiating everything it received. If there is someone who really
wants to do a math problem, I'll measure exactly the transmission line
length, but I suspect that basically the about 60 feet of open wire
helped. I would guess that the antenna reflected a very low impedance
with a large reactive component, and the line length helped in
translating the antenna impedance to something better handled by the
tuner. Therefore, my losses are contained.
73,
Barry
K3NDM
------ Original Message ------
From: "Bill Johnson" <[email protected]>
To: "'Barry'" <[email protected]>; "'Emory Schley'"
<[email protected]>
Cc: "[email protected]" <[email protected]>
Sent: 1/30/2017 9:42:35 PM
Subject: RE: [Elecraft] The "Kinda Random Antenna"
OH YES, the headaches from looking at the formulas at this stage of
the
game. A friend added two coils to the end of his 75 meter dipole for
160.
He loads it but has no clue as to impedance and loading. He tunes it
for
160 but it is not effective. The idea is to get loading into an
efficient
radiator. OK to accept less to operate, but great to be efficient. SO
if
it is working, sometimes leave it alone. Erect another before taking
down
or modifying what works.
73,
Bill
K9YEQ
-----Original Message-----
From
Yep. A good antenna tuner and ladder line hides a whole lot of stuff.
Where would I be with my 40' X 110' yard if I really worried about
being
exact. I have DXCC mixed, CW, and SSB, and I never ran over 100 Watts
nor
had a real "resonant" antenna. And, I've forgotten all of the math I
ever
had in college more than 50 years ago; I get a headache when I think of
ever
having to do math again.
73,
Barry
K3NDM
------ Original Message ------
From: "Emory Schley" <[email protected]>
I've found over the years that a McCoy Dipole works pretty well, often
MUCH better than expected. What is a McCoy Dipole? Named after Lew
McCoy, it follows his rules of construction. "Make it as long as you
can, get it as high as you can, and feed it with ladder-line." No
math,
no measurements, no sweat. But a TUNER (transmatch) is definitely
needed.
Emory Schley
N4LP
Kurt N. Sterba was correct. Textbook antennas aren't always
possible, or even needed. If the situation is difficult, any radiator
is
better than none. However, hams in general are anal animals on the
subject of antennas. My attitude has always been what's a db or two
among friends, and quite often that is the number we are sweating.
But,
if you can't make it exactly like Kraus writes, get as close as you
can
and let your antenna tuner worry about the match and don't think about
that extra db.
73,
Barry
K3NDM
------ Original Message ------
From: "Fred Jensen" <[email protected]>
N6BT famously set up a "phased array" of 3 light bulbs in a V-beam
configuration and achieved WAC. He called it "The Illuminator." Kurt
N. Sterba [a regular in the old WorldRadio] is correct, the power
will
go somewhere. My home antenna is a 136' wire strung along the wood
fence on electric fence insulators. Fed at the end, no overt
counterpoise [the outside of the coax shield handles that]. Not
spec'd
for 160 but the KAT3 matches it fine. Invisible to HOA. NVIS on 160
and 80, semi-NVIS on 40.
One thing to remember: feeding electrically long wires results in
complicated radiation patterns. The higher in frequency you go, the
more it's going to squirt your RF in different directions, not all of
which point at the DX. But, mine works very well considering it's
about 1.8 m off the ground.
73,
Fred ["Skip"] K6DGW
On 1/29/2017 10:26 AM, Barry wrote:
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
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