At 09:13 PM 2/25/07, you wrote:
> >A trade study of going from 4-el to 7-el and whether the ~2 dB of
> >additional peak gain compensates for the ~10 degree reduction
> in >HPBW can be evaluated using a tool like VOAAREA to generate >coverage
> maps.
>
>See above regarding coverage areas. We can forget the HPBW on the
>larger antenna if we are comparing the two antennas. Sure it is
>less. The question is what is the - 5 dB beamwidth of the larger
>one. It is not a fair comparison tfor the larger antenna to just
>say the HPBW is reduced by 10 degrees when it is 2 dB stronger at
>its HPBW than the four element one is at its HPBW point.
In detail, the question is a whole lot more involved than what is the
-3 dB beamwidth of the smaller antenna versus the -5 dB beamwidth of
the larger antenna.
To perform a rigorous, quantitative comparison, I'd want to input
complete patterns (covering all az's & el's) for the antenna systems
being compared into a program like VOAAREA which would predict
received signal levels across my target areas of interest.
VOAAREA outputs a map of the target areas with contours showing where
my signal is S2, where it's S9, where it's 20 over, etc. VOAAREA can
then be used to investigate how my signal's footprint would be
expected to vary with time of day, season, solar conditions, etc.
Which is what I was getting at when I said do a trade study.
73,
Mike K1MK
Michael Keane K1MK
k1mk@alum.mit.edu
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