Rudy Severns wrote:
> I have recently completed a series of tests comparing the signal strength
> between a 40m vertical with 32, 1/4-wave, radials in a complete circle to
> the same vertical with a sector missing from the radial system. This
> represents the case of placing a vertical near an obstruction such as a
> building. Even over my rather good soil the results are discouraging.
> There is signal reduction in all directions but the greatest reduction is
> towards the missing sector. I observed from 0.5 to over 3 dB of signal loss
> in various directions. Over poor soils these numbers would be even worse.
> This does not take into account the loss due to a building in immediate
> proximity to the vertical which is not likely to have a positive impact.
> NEC modeling gives similar results to my experiments, overall signal
> strength is down and the pattern is distorted.
>
> These results will be published in the Nov/Dec 2009 issue of QEX magazine.
> In the meantime I suggest that placing a vertical against a building is
> probably a bad idea. If you have any other option, take it.
>
>
Interesting.. of course, you're talking about a compromise installation
of sorts, so perhaps the 3dB less signal is more than compensated by
more than 3dB less hassle from the HOA/spouse/etc.
It's good to have actual test data. ANother thing I've always
wondered about, but hadn't come up with a good way of testing, is the
added loss from the house next to the antenna. There's going to be some
absorption, but just how much? I guess you could set up a probe some
distance away, and then move the antenna around.
3dB isn't great, but OTOH, it's a reasonable bump for an amplifier (e.g.
if you ran 100W before, a fairly small amplifier would more than
compensate.. at the risk of EMI/RFI or RF exposure limits)..
Of course, if you're "I hate to be weak Mike W4EF" and already running
the limit....
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