When raised or over very poor ground yes, the radial length can affect the
resonance as you have seen. As you add more radials it should become less
pronounced, maybe you haven't reached your 'good number' of radials yet and
were measuring with just a couple?
David Robbins K1TTT
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
> -----Original Message-----
> From: RLVZ@aol.com [mailto:RLVZ@aol.com]
> Sent: Friday, June 24, 2011 22:25
> To: firstname.lastname@example.org
> Subject: [TowerTalk] Radial length question
> Hi Guys,
> I'm at a portable location setting up for Field Day. One of
> our antennas
> will be a 40-meter 1/4 wave ground mounted vertical... with
> a good number
> of radials under it.
> The soil is very poor: 6" of sand with gravel under the
> sand. About as
> bad as possible for a Vertical.
> Common 1/4 wave Vertical theory often states things like:
> "radial length
> does not effect a Verticals resonance when the vertical is
> ground mounted".
> However, I am finding in with this super poor ground
> conductivity QTH
> that the 1/4 wave Vertical wants 1/4 wave radials in order
> for the Vertical to
> resonate anywhere close to where it should. (with odd
> length radials, the
> Vertical's length must be changed by several feet)
> With the above in mind, with this super poor ground
> conductivity, the
> ground mounted vertical behaves more like a Ground Plane
> antenna. I must
> assume this is normal when you have about zero ground
> conductivity. Is that how
> you see it?
> Dick- K9OM
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