Topband: 1/2 wl verticals and spaving

[Carl Braun]

Rick

Thanks for the reply.  

I'm glad to hear that it's that simple.  I used the same principle when the verticals were dedicated to 40M and were 1/4wl tall where I fed them with 3/4wl and 5/4wl coaxial runs.  The gain and side nulls were impressive.

I will invest in some coax and let you know how things develop.

Thanks again

Carl AG6X

-----Original Message-----
From: Richard (Rick) Karlquist [mailto:richard at karlquist.com] 
Sent: Sunday, November 29, 2015 11:02 AM
To: Carl Braun; topband at contesting.com
Subject: Re: Topband: 1/2 wl verticals and spaving

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