A low SWR does not indicate resonance.
Resonance does not necessarily provide a low SWR.
A true quarter wave resonant vertical over a perfect ground plane has a feed
impedance of about 30 ohms and therefore a 1.6:1 SWR "at resonance" (assuming
50 ohm coax).
Seems to me, IIRC, radials for a ground plane should be 5% longer than the
radiator (check the Antenna Book to be sure.)
On Dec 22, 2011, at 5:23 PM, Tom Osborne wrote:
> Hi All
> I just put up an elevated 40 meter vertical. The feedpoint is around 15
> feet or so up and I have 8 radials on it right now. I cut the radials the
> same length of the vertical section. I have a coil of around 8 turns of
> coax for a choke.
> It works good, as the first day I put it up, I worked some Europeans from
> here in Oregon.
> The thing that seems strange is that at the low end of 40, the SWR is around
> 1.3:1. As I go up the band, it goes up to about 1.5:1, then when I get to
> the top of the band, it goes back down to 1.2:1.
> Is that because some of the radials are resonating at different parts of the
> band?? 73
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