Hi, Danny;
Radials under some vertiacl antennas serve to reduce ground losses or, in the
case of elevated verticals, serve as part of the antenna (refer to Jerry
Cevik's discussion on his web site). The far field pattern and field strength
of any antenna is affected by ground characteristics well outside the extent of
radial wires or other conductivity enhancing measures in the immediate vicinity
of the antenna. Good conductivity in the far field reduces losses and
increases the depth of nulls in the elevation pattern. Loss from a salt water
reflection is as little as 1 dB, whereas loss from an earth reflection is 3 dB
or more. Refer to Leo F. McNamara's "Radio Amateurs Guide to the Ionosphere."
I wonder if NEC-2 modeling data for the Sigma 80 is available?
73 de WOØW
Danny wrote:
> John , tnx for posting ur findings on the reflector.
> They were vy useful.
> Im abt to re-join the lowband crowd and currently testdriving
> an inverted L ( with 2 elevated radials ) and a 1/4 sloper connected
> some 30ft up the tower ( i know thats way to low but .... )
> The Sigma 80 is another option , however something on the Sigma 80
> page intrigued me.
> It states : The only thing to enhance the Sigma 80 is to place it
> adjacent to salt water.
> Now , what happens if there is no salt water around ?
> Ground is avg to good around here , but not salty :)
> Is there a way to "imitate" this by using a ground screen ,
> say by using sheets of chicken wire ?
> Anyone an idea about this ?
> tnx
>
> 73 Danny - ON7NQ -
>
> ON7NQ@pandora.be
>
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