>
> Thanks for the clarification, Joe. As to the comment I made about the
> SteppIR being noisier on 20 compared to the A4S, I really have no
> explanation for it. The reverse should be true, and I first put it down
> to
> the notion that the SteppIR was a "hotter" antenna and the lower noise
> level
> on the A4S was because it was more lossy, but the signal levels on both
> antennas with a switched A/B test are virtually the same, the only
> difference is in the background noise level. Often I will switch to one
> the
> A4S's to copy a station that is in the noise. I've discussed this with
> Mike
> at SteppIR and he says the SteppIR should have a better signal to noise,
> but
> it clearly doesn't here at my QTH. All the tribanders are fed with 9913
> which I replace every two years and the runs are quite short because my
> shack is on the 3d floor of my house and two of the yagis are roof mounted
> above me. The SteppIR is on the bottom of the mast with a Cushcraft 402CD
> about 14' above it. The A4S is about 8 lower than the SteppIR on the
> other
> corner of the roof.
Jon,
Mike has mentioned your A4S vs SteppIR S/N situation and we were both
baffled. I think the description of your antenna farm has probably answered
the question. Having a 402CD 14' above the SteppIR (less than 0.3
wavelength) will most likely reduce the F/R performance of your SteppIR.
For example, I have found that installing a 2M beam within 0.6 wavelength
(4') of a 6M beam will start to seriously impact the F/R and forward gain of
the antenna. Whenever one or both of those numbers goes down, your S/N
ratio will suffer. I haven't modeled your exact scenario, but in general a
lower frequency antenna that is mounted too close vertically to a higher
frequency antenna will reduce the F/R of the higher frequency antenna,
sometimes significantly. I don't have a good NEC-2 or EZNEC model of the
402CD, but I'll try some short 2 element 40M antenna models that I do have
mounted 14' above a SteppIR and let you know what I find.
What is the height above ground of your 3 element SteppIR and the Cushcraft
A4S? Height above ground can also impact the F/R of the antennas and
different antenna designs can react differently at the same height.
73,
Clay W7CE
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