Back to your question - you should declare VICTORY! The wide bandwidth
may be due to the various lengths and/or couplings of the elevated
radials. There is nothing to indicate you have high losses in your
antenna system and you are happy with the performance. You have more
than enough radials for an elevated vertical, see the recent QEX and QST
articles. On 40m your SWR losses are negligible with RG8.
I've tried EZNEC on elevated radial systems for 40 and 80m, including
metal roofs and found that the code has a hard time with them, the
results are very sensitive to system ground locations and parameters.
So, I think it is difficult to design/make for perfect resonance or 1:1
SWR, whatever you think best with real elevated radial HF vertical antennas.
The only thing I would suggest is to put a better choke balun at the
feedpoint - see K9YC's designs using Type 31 ferrite toroids.
On 12/22/2011 2:23 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
> Tom W7WHY
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