In a message dated 98-03-13 19:15:00 EST, N7CL writes:
<< Ground level (far field) field strength measurements are
perfectly adequate to verify and compare the performance of these
systems. The screen density affects only the radiation
efficiency of the system. It does not significantly modify the
radiation pattern of the antenna in the elevation plane. So a
change in the "ground wave" field strength is accompanied by a
proportional change in the intensity of the radiation in the
antenna's main lobe which is launching the sky wave. >>
Hi Eric, (and Tom)
I enjoyed your info, I have not done much experimenting with verticals, I am
very much interested in them now that I will have room for some and after I
saw how VE1ZZs verticals next to salt water play. But ....
On your above statement, I have seen in the books that radiation diagrams
for verticals, with poor ground would have the part of vert. radiation pattern
"missing" at low angles, better ground (salt water) seem to fill that pattern
all the way down to almost 0 deg. Isn't the situation between few and lot of
radials analogous to poor and good ground? Therefore affecting the signal
strength of "mile away on the ground measurements"? Woudln't the difference at
some higher angle like 30 deg. be less pronounced? From amateur point of view
we might be more (90% or so) times interested in the efficiency at that higher
angle due to propagation modes on 160. I can see why broadcast stations are
interested in omnidirectional pattern and maximum signal at the ground level
(why don't they use crossed low dipoles?). But for our ham radio purpose, I am
looking more for launching my signal at the best optimum angle in the most
favorable direction at the time. Has anyone done A - B tests on DX signals
between big screen and few radial verticals (or a half wave sloper) ?
73 Yuri, K3BU, VE3BMV
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