RadioBanter - View Single Post

December 23rd 03, 09:04 PM

On 23 Dec 2003 10:27:38 -0800, (Art Unwin KB9MZ)
wrote:

That commercial radio stations use tines is evidence to me that they
serve a purpose i.e. electrostatic shielding, not everything, just
electrostatic stuff

And what have I written that would suggest otherwise?

( ignoring harmonics e.t.c. )

Ignoring harmonics? Read your Terman. Read Richard Harrison's
postings.

As for low frequency use, that would include audio, not just 50/60
which you refer to 'power .

Faraday shields are used universally there for the same reasons they
are used in ELF/VLF/LF/MF/HF/VHF/UHF so there is absolutely no
argument to made for or against ANY band. As I said, wavelength and
physical size dominate ALL considerations and no one is talking about
a 6 inch shield used in the SHF.

Or are you?

Now you say look at Terman and I have, not
only the section on transformers but on coupling circuitry...way back
to the days of spark gaps and ticklers, each of which are treated
differently by not only Terman but also by others.

Art, did you actually read Terman? You offer nothing in that regard
to support or negate any discussion here. I have references going
back to the spark gap days of 100 years ago and nothing there bears on
any of this additional discussion you are bringing to the mix.

For the mythical lurker, such a reference is found on page 39 of
"Electronic and Radio Engineering" (1955 ed.) and specifically to the
matter of tines in problem 2-45. The matter of its construction is
strictly a matter of convenience as solid conductors would work as
long as there is no complete loop introduced by grounding the sheet at
two (2) points. This, as I've pointed out in recent posts, is the
commonplace of neophytes going hog wild making multiple grounds and
"curing" problems where the cure kills the patient. This last comment
is the assignment to Terman's problem. He pointedly uses the one word
imperative: "Explain."

You will also note
that audio cables have sheet like covering just like books do with
TOTAL shielding. Pretty much all books on fields and waves have a
section of total shielding of nearby circuits with special reference
to TOTAL enclosure and the effects on circuits or inductances that are
so enclosed.

There is no such thing as total shielding from these rather ordinary
sources you have access to; except as an academic wet dream argued by
philosophers who have not actually had to perform a total shielded
solution. Some of the worst interference problems I've solved have
come from "totally shielded" designs by pHDs. Again, wavelength and
physical size will not be denied.

With all that being said and getting back to the initial area of
discussion
where Richard alluded to the picket fence. Why do you think that the
broadcast industry hung on to the ungainingly picket fence after all
these years and why would it not descriminate with regard to other
influences ?

Best regards
Art

Hi Art,

To answer your last question - there are far more issues considered in
the practical world of commercial design that require no proof through
cut-and-paste philosophies. In simple terms, Production Engineering
works and its success does not breed the need for a new science or
physics. Just as fractal antennas work (any hank of wire does too);
there was no need to proceed to invent a fractal electromagnetics to
tart up the "new" idea (those mantles of nobility didn't add even a
tenth dB more gain for all the pHd's efforts to publish).

73's
Richard Clark, KB7QHC