Hi Roelof, thanks for those measurements. I am guessing that there is some
effect from the roof at "zero height" as I would only expect doubling the
height to give 6dB. It looks like the "effective height" is measured from
the roof in this case. height about 1.5m , multiply by 4 for 12db at 12m is
about right. Strange !
However it certainly demonstrates the importance of height with a e-field
probe.
I think Dave G3YXM found a bit difference when he elevated his a bit more.
I suppose it could be the effect of buildings on the wavefront despite the
fact that they a much smaller than a wavelength.
Thanks and Cheers de Alan G3NYK
----- Original Message -----
From: Roelof Bakker <[email protected]>
To: <[email protected]>
Sent: 28 January 2006 13:09
Subject: LF: Re: Re: Re: Re: Re: Mini Whip and local noise
Hello Alan, LF-group,
In my notebook some more height versus signal level figures were found.
This was a test on my semi-flat roof, starting 1 metre above the roof and
7
metre from the ground.
height rel. dB
=================
7 m / 23.0 ft 0 dB
8 m / 26.2 ft + 4 dB
9 m / 29.5 ft + 6 dB
10 m / 32.8 ft + 9 dB
11 m / 36.0 ft + 10.2 dB
12 m / 39.3 ft + 11.5 dB
As said before, signal to noise ratio did not change with height.
Best regards,
Roelof Bakker, pa0rdt
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