> Just imagine how it would look if there were LOTS of radials
> all connected so it approximated a solid metal plane, that is
> what the raw designs are compared to, a perfect conducting plane.
Elevated radial systems do not have nearly the "sinking capability"
as an infinite, perfectly conducting ground plane. In a perfect
world, if the vertical was fed by coax from underneath an infinite,
perfectly conducting groundplane, there would be no common mode
currents on the feedline and there would be no current flowing
between elements on the groundplane (perfect sink).
However in the real world, elevated radials must be resonant (or
must resonate with their vertical element) and since they are not
perfect sinks if they are connected together current will flow
from one feedpoint to another bypassing the phasing/feed network.
The net flow will also induce (additional) current in the earth
since the field will be unbalanced resulting in increased ground
losses.
These are nothing but the inevitable application of the principles
of electromagnetics - basic physics.
> -----Original Message-----
> From: cq-contest-bounces@contesting.com
> [mailto:cq-contest-bounces@contesting.com] On Behalf Of David
> Robbins K1TTT
> Sent: Wednesday, January 30, 2008 5:07 PM
> To: 'reflector cq-contest'
> Subject: Re: [CQ-Contest] 4 Square/ Raised Radial Questions
>
>
>
> Sounds like something wrong with that box to me. On my 4-square the
> feedpoints are all connected by radials, the feedlines all
> connect to the
> bases and the switchbox just like another radial... and it
> definitely works!
>
>
> Just imagine how it would look if there were LOTS of radials
> all connected
> so it approximated a solid metal plane, that is what the raw
> designs are
> compared to, a perfect conducting plane. The currents are
> injected at the
> bases of the verticals with no need for feedlines
> baluns/chokes or anything
> else, the model works just like the real thing... or vice versa.
>
> David Robbins K1TTT
> e-mail: mailto:k1ttt@arrl.net
> web: http://www.k1ttt.net
> AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
>
>
> > -----Original Message-----
> > From: cq-contest-bounces@contesting.com [mailto:cq-contest-
> > bounces@contesting.com] On Behalf Of k3bu@optonline.net
> > Sent: Wednesday, January 30, 2008 14:41
> > To: reflector cq-contest
> > Subject: Re: [CQ-Contest] 4 Square/ Raised Radial Questions
> >
> >
> >
> > > How can the current on the outside of the shield of the coax
> > > upset a phasing
> > > network that is in an all metal box?
> > >
> > >
> > > David Robbins K1TTT
> >
> > Just picture wire connecting bases of all verticals,
> connected at the
> > phasing box.
> > The best demonstration of the effect is the 3 vertical
> array fed by Stack-
> > Match phasing unit, advertised for this purpose too.
> > The result? 3 el. omnidirectional antenna, regardless where
> you beam.
> > I have used it with three vertical array, each with 4
> elevated radials,
> > using baluns at the antennas, but still no difference in
> the pattern.
> > The problem was that coax shields were connected at the
> phasing unit.
> > Breaking the shields connections solves the problem,
> confirmed by other
> > users.
> >
> > 73 Yuri, K3BU.us
> >
> > _______________________________________________
> > CQ-Contest mailing list
> > CQ-Contest@contesting.com
> > http://lists.contesting.com/mailman/listinfo/cq-contest
>
>
>
> _______________________________________________
> CQ-Contest mailing list
> CQ-Contest@contesting.com
> http://lists.contesting.com/mailman/listinfo/cq-contest
>
>
_______________________________________________
CQ-Contest mailing list
CQ-Contest@contesting.com
http://lists.contesting.com/mailman/listinfo/cq-contest
|