From Tom, G3OLB
Andre
I'm not at all clear how this antenna is matched and fed. I am
particularly interested because I currently use an 1100 ft end fed wire
which I could conceivably extend to a full quarter wave. Like yours it
is suspended from a number of trees but high voltages are not a
particular problem because I have it well insulated with some good
ceramic insulators (thanks Dick!) There are also cows in my field but
they are a well insulated breed.
Your 1600 ft antenna is approaching a quarter wavelength long and, as
Dave says, opposite ends of a quarter wave antenna will present opposite
impedances i.e. if you leave the far end open, the near end will look
like a low impedance and conversely if you ground the far end, the near
end will be high Z. So I cannot reconcile grounding BOTH ends and being
able to resonate it.
73, Tom G3OLB
In message <[email protected]>, Andre' Kesteloot
<[email protected]> writes
Wooops,
I guess I did not express myself quite clearly enough.
The far end of the wire terminates in a field , (and specifically near a pond)
visited by many cows. In order to avoid any possible unpleasantness (wire
falling on the ground if broken by the wind, etc.), we decided to ground that
end.
It may well be that the whole thing operates as a loop of sorts, as there is a
non-zero resistance between the two grounds (the one at the Tx site, and the one
at the pond end)
73
Andre'
Dave wrote:
Surely the Voltage gradient is just the same but the other way round? High
current point at the earthed end and high Voltage point at the TX site as it
is about a quarter wave....
The "earthed at the far end" idea has been used with topband antennas for
years in order to get the current into the vertical drop.
73 Dave G3YXM.
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