Topband: 1/2 wl verticals and spaving

[Richard (Rick) Karlquist]

On 11/28/2015 6:23 AM, Carl Braun wrote:

> Any suggestions or websites available on ½ wl spacing and ½ wl radiators?
>
> Carl AG6X
>

I did some modeling of this a long time ago.  Basically, the
issue is that if you feed the 1/2 wave verticals at the base,
you need to have a *voltage* forcing feed, rather than the
usual current forcing feed used for 1/4 wave verticals.
This is tough to do if you need a 90 degree phase shift as
in a 4 square.  However, you are in luck because you only
need a 0 degree or 180 degree phase shift.  As long as
your array is physically symmetrical, any symmetrical feed
network will give the right phasing.  I suggest a simple
T junction (in coax) with 1/2 wave lines to the verticals.
Make one of them 3/2 wave for 180 degree phasing.
The impedance at this point may be too high for an off
the shelf transmatch, so you might have to roll your own.

Rick N6RK