Thread: Facts
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Old November 7th 04, 12:35 AM
Cecil Moore
 
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Yuri Blanarovich wrote:

W5DXP wrote:
There is forward current flowing into the bottom of the coil and out
the top. There is reflected current flowing into the top of the coil
and out the bottom. The net current is a standing current wave.


In view of the above, for practical putposes, trying to get maximum performance
out of the loaded radiator, it should be beneficial to have the same diameter
of whip above the coil, rather than tapering whip?


That doesn't help much. What helps is a humongous top hat which does
help to equalize the current at the bottom of the coil and the current
at the top of the coil.

One might deduct that if the current is diminishing towards the top, that the
diameter of the radiator (RF resistance) could be tapered also. But since the
RF current has to flow to the tip and then reflect and go back and interfere
with itself, we should make it uniform, where possible.
We are probably talking about fraction of a peanut, but for the purists and
sake of argument.


Nope, not a fraction of a peanut at all - more like 100% more radiated
power because of that humongous top hat. I'm considering a humongous top
hat for my pickup that runs the length of the truck and is mounted about
a foot above the cab - maybe 50 square feet in all. That would minimize
the size of the loading coil and ensure maximum current in the bottom
section. The maximum height above ground would be about seven feet, a
definite advantage for a mobile antenna around here.
--
73, Cecil http://www.qsl.net/w5dxp


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