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[aprssig] 9600b UHF APRS IS THE FUTURE OF APRS

Patrick Green pagreen at gmail.com
Mon Oct 9 17:55:16 UTC 2006


I operated 9600 on UHF for a short time along side the VHF digi currently
running and the performance was disappointing.  I have a problem at that
site with long runs of feedline and can't keep the loss figures managable.
VHF is more forgiving.  While in opation, I had to fish for a spot most of
the time while the system was running.  It was running a Kantronics D4-10
running 10 watts on 430.55 to a 6 dbd omni at 80 feet.  The 200 foot run of
feedline (90 feet of 7/8" heliax and 110 feet of RG-214U) made for some
dismal loss figures.  Compound that with the fact that 430.55 is away from
where the antenna was cut for (448) and the D7A probably isn't optimized to
receive at that end of the range.  When mobile, I could get in as long as I
was 4 miles of less from the station.  Stationary, I could get in up to 8
miles or so away.  Now compare that to the 2m system which has a
5.25dbdgain antenna cut for
146.52 with 200 feet of RG-214U at the same height, I can get into it from 8
to 9 miles away moving and as far as 20 miles away stationary with the same
D7A.  Just thought I'd pass this along.

73 de Pat --- KA9SCF

On 10/9/06, Bob Bruninga <bruninga at usna.edu> wrote:
>
> > I wish the FCC would come along and declare the
> > future of APRS will be on 440 at 9600 baud,
>
> Depends on what one thinks APRS is.
>
> This clamor for 440 at 9600 baud flies in the face of physics if you want
> good general coverage. VHF is 9 dB better than UHF for omni antnenas (think
> mogbiles) AND
> it has less multipath and fades.
>
> So APRS at UHF may have practical applications, but serving as a general
> distribution it will never be as "good" as VHF.  SUre all those problems can
> be fixed with 3 times more digis to cover the same area, but I doubt it will
> ever be practical for general coverage like VHF.
>
> Bob
>
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