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@karlquist.com]
Sent: Sunday, November 29, 2015 11:02 AM
To: Carl Braun; topband@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
_________________
Topband Reflector Archives - http://www.contesting.com/_topband
|