I sent Roy a copy of the EZNEC file that I sent to you. Anyone else
who wants a copy of those files, send me an email.


I didn't get it, for direct mail take noSaddam out :-)

I will post your comments on eHam.net.

Which forum/topic?
--
73, Cecil, W5DXP

The article and follow up comments are at:

http://www.eham.net/articles/6512

Yuri, www.K3BU.us

G4FGQ:

When ground loss is very small (zero if antenna is a pair of two
back-to-back radiators to form a dipole) efficiency is relatively high
anyway, maximumum efficiency perhaps occurring with the coil located in the
lower half of the antenna. The slight improvement relative to base loading
(as part of a tuner) may not then be worth the mechanical inconvience of
fitting a coil in the antenna anyway.


But not in the far field, affecting low angle radiation. Practical results and
measurements show that it is worth the mechanical inconvinience to place the
coils where they belong. Just ask Cecil about results of mobile antenna
shootouts.

An important factor, not considered quantitatively by anybody, is that a
mobile antenna is not just a loaded vertical - the vehicle body, just by
looking at it, obviously forms the major portion of the antenna and is
floating above ground.

At this time it is "bad" enough to look at this one aspect of loaded antennas.
Of course in mobile antennas, the vehicle plays important role. W9UCW excluded
that, used "perfect" radial field ground to eliminate other variables in order
to have a closer look at the current distribution.

Another interesting finding was that there was almost negligible difference in
Q of coils. When they compared "perfect" loading coil (Bugcatcher type) with
"poor" coil of Webster Bandspanner, thay saw fractions of dB difference.

Yuri, K3BU/m

Yuri Blanarovich wrote:
Practical results and
measurements show that it is worth the mechanical inconvinience to place the
coils where they belong. Just ask Cecil about results of mobile antenna
shootouts.

I feel the same way, Yuri, but at a shootout, +2dB is worth it's weight in
tachyons. +2dB may or may not be noticeable during normal operation. I use
a screwdriver even though I know how to do better.
--
73, Cecil http://www.qsl.net/w5dxp



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Yuri Blanarovich wrote:
The article and follow up comments are at:

http://www.eham.net/articles/6512

Egads, did I get the last word? (so far) That's proof of action
at a distance. I'm a thorn in the side of hams who are not even
on the same newsgroup as I. :-)
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil Moore wrote in message ...
Yuri Blanarovich wrote:
The article and follow up comments are at:

http://www.eham.net/articles/6512

Egads, did I get the last word? (so far) That's proof of action
at a distance. I'm a thorn in the side of hams who are not even
on the same newsgroup as I. :-)

Dunno...I finally got up enuff courage to wade thru a bunch of that
myself. Both had some decent points..But....Just using my built in
"BS" filter only, which rarely seems to fails me, and ignoring all
other influences, I still have to side with Tom. I still think the
current is fairly constant. But not perfectly so, and can vary due to
the antenna and it's mount, etc. I guess I'll just wait until the
smoke clears to see how far off I am. This will be a good test of my
filter unit. :) As far as who wins, I could care less. Nothing
personal either way...But I have learned never to ignore my BS filter,
so I'm going with it. :) MK

But....Just using my built in
"BS" filter only, which rarely seems to fails me, and ignoring all
other influences, I still have to side with Tom. I still think the
current is fairly constant.

Nothing
personal either way...But I have learned never to ignore my BS filter,
so I'm going with it. :) MK


Same here,
did your filter filtered out W5DXP pudding? The "theoretical" proof is right
there. Or are you drinking the same coolaide as Tom? :-)

Yuri

Reality vs. Speculations? Duuuh?

Mark Keith wrote:
Dunno...I finally got up enuff courage to wade thru a bunch of that
myself. Both had some decent points..But....Just using my built in
"BS" filter only, which rarely seems to fails me, and ignoring all
other influences, I still have to side with Tom. I still think the
current is fairly constant.

The key to understanding is to realize that the net current is the
phasor sum of the forward current and reflected current (on a standing-
wave antenna). Assume a 10 degree phase delay through the coil on the
frequency of operation. Ifwd-in and Iref-out are on the same side of
the coil. Ifwd-out and Iref-out are on the other side of the coil.

Ifwd-in-- coil Ifwd-out--
-----------------------////////////-------------------------
--Iref-out --Iref-in

Assume that |Ifwd-in| = |Ifwd-out| which satisfies Kirchhoff

Assume that |Iref-in| = |Iref-out| which satisfies Kirchhoff

Ifwd-in + Iref-out = net current on left side of the coil

Ifwd-out + Iref-in = net current on right side of the coil

Ifwd-out lags Ifwd-in by 10 degrees

Iref-out lags Iref-in by 10 degrees (Iref-in leads Iref-out)

Now let's assume that Ifwd-in and Iref-out are in phase. So current
on the left side of the coil equals Ifwd-in at zero degrees plus
Iref-out at zero degrees which is a current maximum point.

Ask yourself: Can we have a current maximum point on both sides of
the coil? I trust that answer is obvious.

Ifwd-out lags Ifwd-in by 10 degrees. Iref-in leads Iref-out by 10 degrees.
So current on the right side of the coil equals Ifwd-out at -10 degrees
plus Iref-in at +10 degrees, NOT a current maximum point.

Therefore, in this example, net current on the left side of the coil
cannot possibly be equal to net current on the right side of the coil.
--
73, Cecil http://www.qsl.net/w5dxp



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Yuri Blanarovich wrote:
Same here,
did your filter filtered out W5DXP pudding? The "theoretical" proof is right
there. Or are you drinking the same coolaide as Tom? :-)

Yuri, my latest posting sheds more light. Apparently, W8JI doesn't
realize that there are two superposing currents phasor-adding together
to get the net current and the phase distribution between those two
current waves are opposite because they are traveling in opposite
directions. This is a characteristic of standing-wave antennas.

See what happens when one tries to ignore the component waves?

Because the two currents are traveling in opposite directions, any phase
delay through the coil shifts the phase of the two currents IN OPPOSITE
DIRECTIONS. Thus the total relative phase shift effect through a 10 degree
coil is 20 degrees.
--
73, Cecil http://www.qsl.net/w5dxp



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Therefore, in this example, net current on the left side of the coil
cannot possibly be equal to net current on the right side of the coil.
--
73, Cecil http://www.qsl.net/w5dxp



Thanks for another gem,
I apologize to Reflected Waves, for they are important and I will treat them
with greater respect. I still don't like them in the feedlines, but I love them
in the radiators :-)

Yuri, www.K3BU.us

Yuri Blanarovich wrote:
I apologize to Reflected Waves, for they are important and I will treat them
with greater respect. I still don't like them in the feedlines, but I love them
in the radiators :-)

Yuri, to be perfectly consistent, you would need to change all your
standing-wave antennas to traveling-wave antennas. I've got some
non-inductive terminating resistors for sale at the right price. :-)
--
73, Cecil http://www.qsl.net/w5dxp



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