I sent this message to K9LA, then it occurred to me that maybe I should
sent it to the group also. So here it is.
I agree that BOGs are not well understood. What started this whole
process of comparison of measured data to NEC predictions was the fact
that with simulations I found a way of improving the front to back of a
long BOG by 20 to 25 dB. Before I went proclaiming this "amazing"
improvement, I wanted to know if it was real or not. I actually built
it but could see no improvement, however I had other problems that may
have masked what I was looking for. Next season I was planning a better
version.
To gain some confidence in what NEC was telling me, I started making
measurements and found some very unexpected results. Current values were
way off, and with my simple dipole on the ground measurement I was
unable to duplicate the resonant frequency using any and all ground
parameters possible in NEC. The only conclusion possible seems to be
that either I made some bad measurements or NEC is incapable of modeling
my ground, whatever it is (which should be common Alabama red clay).
N6LF's test equipment is certainly better than mine and I was hoping for
some data I could use for comparison purposes.
Another reason for all this analysis and measurements was to explain why
most people say the best length for a BOG for 160 is between 200 and 250
ft. NEC says that a much longer BOG is much better. Is it? NEC says
the pattern for a 250 ft BOG is identical to a K9AY. Some people have
probably made that comparison, but I haven't.
Jerry
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