"K7ITM" wrote in message
ups.com...
Roy wrote, "It's not hard to demonstrate that the (time-varying)
magnetic field
doesn't penetrate a non-ferrous shield, if you believe (correctly) that
a time-varying magnetic field will produce a current on a nearby
conductor."

Yes, it's all easy to demonstrate. It's used in practice all the time:
the shielding in a transmitter, the aluminum shield cans around IF and
RF coils, the copper strap around a power transformer (used
specifically to lower the external magnetic field around the
transformer, so it won't couple into low-level audio circuits or affect
colors on a color CRT).

And indeed it all agrees with theory. For this one, you need little
more than Faraday's Law of Magnetic Induction.

It's fine with me if there are people who don't want to be bothered
with theory, but if they profess that something works by means
different from the theory that I understand and which agrees with the
observations I make, they shouldn't expect me to believe them without
putting some very serious effort into explaining why the accepted
theory is wrong. I believe Yuri when he tells me his antenna works.
But I'm not buying into his explanation of HOW it works.

Cheers,
Tom

I am not selling explanations how it works.
I understand your and Roy's points. I am not claiming to try to formulate
the infinitesimal theory of wasaaaap and I didn't try that with loading
coils. Ensuing discussions helped me to better understand the mechanaism of
how things work, the theory and how can I better apply them. I thank you for
that.

What I have problem with someone claiming shield is not a shield (Why do
they bother calling it shield or shielded loop?), when I saw the shielding
properties of it in the vicinity of the local interfering signals. It
performs as a shield to the antenna that is wound inside. Tom categorically
denies SHIELD, it IS the ANTENNA he claims. (Like there is no current drop
along the loading coil! - The gospel from the all-knowing guru.)
What I have problem with someone claiming the small loop antenna (three plus
one turn) is not the antenna, but when I remove the shield, the "not
antenna" is still THE ANTENNA.

I am not arguing the mechanics or theory behind how the shield works, it may
be transparency to magnetic field, it may be the voltage generated in the
gap, bla, bla...
Based on my experience with the said antenna, I concluded that wire loops
are THE antenna, shield works as an electrostatic shield.

I know that if I stick oscillator inside of 10' of 1/2" tubing, I will get
hardly or no signal out. I know if I bend that tubing into a circle with gap
and stick wire loop antenna inside, I can get signals out of that "shielded"
antenna and can attenuate close by interfering signals. Shielding doesn't
MAKE my antenna work (it works without shield too), shield enhances its
rejection/shielding properties in near fields.
I know there are small loops and there are small shielded loops and they
work and I have proved it.

Just don't tell me it is called shield because it is antenna, or that
antenna inside the shield doesn't work, or shield doesn't shield from
electrostatic fields, or that my antenna I described doesn't work as I
described.

Tom may pontificate his ideas to his worshippers, but I don't swallow that.
I point out my, and who else cares, disagreement, especially when I see his
"ideas" migrating into ham literature.

Go ahead with your but, but, butts.....

73
Yuri Blanarovich, K3BU, VE3BMV