E/M radiation from a short vertical aerial
"Spike" wrote in message
...
Thanks for the comments, Jeff. Perhaps I'm not being clear enough.
Look at the issue this way.... While it's clear that the totality of the
e/m emissions from from the antenna depend on factors such as length,
height, and ground, (and I originally assumed a particular set-up in the
OP) there are three distinct methods by which such a transmission can be
received: the sky wave path to a distant receiver, a space wave to a
line-of-sight receiver (that could easily be outside the surface wave
range) and the surface wave to a receiver tucked into the far side of a
hill with no sky wave or space wave path. It can be expected that
increasing the transmit power will increase the received signal at all
three locations, but the question I'd like to see answered is: what
proportion of the power supplied to the antenna goes to each of these
three phenomena, which all arise every time the transmitter is keyed. They
might all be connected by the conditions you mention, I'm not suggesting
they aren't, but for the set-up I originally described, what are the
proportions of the power supplied to the antenna that contribute to each?
Or, to put it in yet another way...There might only be one 'wave' launched
from the set-up, that propagates in three different 'modes' (for the want
of a better word); so what controls the relative power/energy with which
each 'mode' is propagated?
You have to get it in your head there is not 3 differant waves launched from
the antenna. There is only one wave. As it leaves the antenna, whatever
the wave hits determins if it is ground, sky or whatever. The patern of the
antenna determins how much goes where.
With some antennas the patern is such much of it goes out to the horizon and
not much up in the air. Others radiate much to the vertical and not much
toward the horizon.
Think of it as throwing a rock into the middle a small pond. If there is
noting in the pond, the wave will go out toward the edges equally. If that
same rockis thrown in near the edge of the pond, some of the ripples will n
hit th eedge of the pond near the rock first while it will take some time
for the ripples to hit the other side.
You have the same origional wave, but its propogation is modified as to
where it is at . You do not have seperate waves leaving the rock.
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