[Antennas] Lenght of W3EDP

2002年5月17日 20:10:06 -0400

At 07:36 PM 5/17/2002 -0400, Joe Falcone wrote:
>I was reading about the W3EDP. About 85 feet of long wire and 17 feet 
>counterpoise.
>>What if you double the length will that help?

Joe,
A truly "long wire" is generally considered to be over a wave length long, 
and it has directivity and gain. The longer it is, the more directive it 
becomes and the more gain it has, and the direction of maximum gain gets 
closer to the axis of the wire. That can be a disatvantage too, because it 
has deep nulls, and does not have good coverage around the compass.
>I don't know if the question about the "optimal longwire" was ever 
>directly addressed. Are you better off with the longest wire you can put 
>up, or should you just stick to 85 feet, let's say? Thanks, Joe.

85' is a compromise, giving coverage from 40 through 15, and with a ground, 
coverage includes 80 and 10. It exhibits directivity on 10 where it is 
about 2 wavelengths long. So some 10 meter signals are stronger on the 
W3EDP and some others are stronger on my vertical.
If you want a directive antenna on a particular band to point to an area in 
the world, a long wire will do it. But you can't rotate the antenna, and 
you will have decreased gain in other directions.
73, Chas, W1CG