Richard Clark wrote in message . ..
On 30 Jan 2004 02:16:09 -0800, (Maurizio) wrote:
Hi Richard,
my feeling is that in the past some studies have tried to find out the
structure and relative strenght of the ground/space wave fields.
Experience has then given rules to evaluate the losses due to the high
reactive fields near the antenna with the lossy ground (i have seen a
paper using a 6 dB factor to take into account antenna mismatch and
such nearby losses).
It maybe that this is almost all that has been done.
Do you agree?
Maurizio
Hi Maurizio,
I worked on this a couple of years ago:
http://home.comcast.net/~kb7qhc/ante...elds/index.htm
It deals not so much with the variation of ground proximity with a
standard antenna, instead it works against the standard ground with a
variety of antennas.
Due to the intricacy of geometry afforded by a fractal form, this:
http://home.comcast.net/~kb7qhc/ante...atic/index.htm
is the most interesting. Unfortunately, the legacy of academic
fractal research (sic) has offered no more interest than the morbid
study of Down's Syndrome among the Armadillo population.
73's
Richard Clark, KB7QHC
Hi Richard,
It seems that you have tried to shorten somewhat these cumbersome
antennas with the fractal approach.
I have seen recently an interesting paper on antennas & propagation
proceedings/magazine that was comparing the performance of fractal and
non-fractal designs.
Regarding the graphs you show in the web pages, if I have well
understood, you compare the E/H local fields (amplitudes) with the
free space impedence.
It is an alternative way to look at the near reactive fields.
However, the antenna that was simulated in the paper I was talking
about is a real antenna that has been modellized with a dedicated MOM
program and with the correct antenna geomety, and results have been
compared with measurements.
From this comparison it has been necessary the introduction of such
factor.
It seems to me that the 6 dB factor had to take into account all
losses from the transmitter to the radiated fields.
My concern is how this factor can be justified.
6 dB is a lot in terms of antenna usefull coverage distance.
Maurizio