Faraday shields and radiation and misinterpretations
On Thu, 03 Dec 2009 02:28:26 -0600, Lostgallifreyan
wrote:
Regarding the other postings today, I can see that if you're receiving a long
wave signal a small system will do if the sensivity is good and the noise is
low, but transmission is another matter entirely.
Reciprocity dominates, but transmit and receive circuits are not
always reciprocal (that is, symmetric or identical). If you match at
the antenna, you don't lose signal in the loss of the transmission
line where SWR would dominate. That topic is best left to other
discussion.
But whatever the theories
propounded might be, I guess the observations are what matters. I haven't the
space or equipment to test it, but if anyone manages to transmit a lot of
longwave RF from a small directional system such as Art Unwin appears to be
describing, then the theory will take care of itself, eventually, but I also
get the strong impression that few people, if any, have done it. As far as I
know, all low frequency RF transmitting systems are large, powerful things,
and not very directional.
In logic there is the argument called Reductio Ad Absurdum. With the
claim of a resonant small antenna being efficient there exists an
obvious example that completely disrupts this. Since the inception of
man-made RF radiation, ALL such attempts have been preceded with a
resonant coil/capacitor combination. Think of the plate load of the
conventional RF transmitter in both amateur and professional
applications for the many decades that followed Hertz' work.
This small, resonant plate load, is quite specifically designed for RF
with low in resistive loss - and yet it is miserable as a propagator
of that same RF. The physical size compared to the wavelength size
dominates that efficiency with a fourth power law. Hertz' original
design was in the VHF where his "plate tank" (so to speak) was
physically large in relation to the wavelength he successfully
transmitted to a nearby physically large receiving tank.
73's
Richard Clark, KB7QHC
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