Topband: modeling BOGs (or whatever we call them)

[K4SAV]

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