> a 2 vertical array (on 40m in this case, and projecting it to be
> switchable), please debate the merits of the "cardiod" pattern by
> feeding 90-degrees out of phase (3db gain by the ON4UN book and best
> f/b) and possibly feeding 135-degrees out of phase (4.9db gain by the
> book and small back lobe)? It's a gain vs. f/b question.
The F/B ratio of the 135-degree phased antenna will actually be
more useful and appear higher than the 90-degree phased antenna.
That's because the 90-degree phased antenna has a single null
area at ground level directly off the back. That's the last place we
want a null when working skywave.
When 135-degree phasing is used, the null forms a deep slice in
the shape of a cone that is at two points off to each side of the rear
at zero-degree elevation. As you move towards the back, the null is
elevated and reaches its highest point directly off the back.
The reason the 135-degree phased antenna has more gain is it has
a wider null area. A wider null area up in the air is much more
useful to us than a single null directly off the back centered along
73, Tom W8JI
FAQ on WWW: http://www.contesting.com/FAQ/towertalk
Administrative requests: towertalk-REQUEST@contesting.com