[OZAPRS] FW: [Fwd: 70 cm APRS frequencies]

[Bob Bruninga]

UHF APRS:
This did NOT go out to the yahoo groups because I am not a member.
If you find it worthy of the group, you might forward it..
WB4APR

On Thu, 20 Nov 2003, Bob Bruninga wrote:

> On Wed, 19 Nov 2003, Richard Hoskin wrote:
>
> > When this subject came up a year or two ago John Martin/Peter
Hallgarten
> > suggested we use 439.100Mhz for a National UHF APRS frequency but due
to
> > the other issues the WIA never ratified this in the band plan.
>
> WB4APR's 2 cents for what its worth...
>
> 1) APRS is a SINGLE frequency tactical system for end users.  There is
no
> need or desire (in general) for other than one freq.  Everyone wants and
> needs to be "where the local action is"...  (If everyone is not on the
> same channel, then everyone is not seeing the same tactical information)
> and you dont have a real-time tactical system...
>
> 2) UHF for single UI mobile packets is MUCH WORSE than VHF due to
> triple the mobile flutter rate and 9 dB worse path loss dipole to dipole
> and 7 dB worse modem detection...
>
> 3) APRS needs  UHF backbones to tie the long haul packets between end
> users on local LANS operating on the single national frequency.  These
> cross links and backbones CANNOT all operate on a common UHF frequency
> (hence, there is no need for a "common APRS UHF frequency))...
>
> 4) Mobiles (think Kenwooods and HAM-HUDS) have NO NEED for LOTS of
> incoming megabytes of positions from anywhere but their local area.
They
> cannnot display it and the driver cannot ABSORB IT.  THus there is NO
NEED
> for UHF or 9600 baud to imporve the SPAM rate to mobiles...
>
> 5) CONVERSLY, those with full displays and PC's are usually fixed.  THey
> DO WANT TO SEE lots of stuff.  But they are FIXED and LOCAL and so they
> have no problem "remembering" their local UHF backbone or LINK.  Again,
> there is no need for a common (mutually interferring) high speed UHF
> backbone frequency.  For best integration, it is desired that all high
> speed UHF feeds use DIFFERENT channels to completely avoid the mutual
> interfere3ce and to give dedicated full time access.
>
> So my conclusion after looking at this for YEARS, is that there is just
no
> need for a single coordinated UHF APRS channel.  But there is a need for
> EVERY local APRS lan to coordinate a LOCAL UHF channel (different from
> their 4 neighboring LANS) to feed high speed data to the LAN...
>
> Just my two cents...
> de WB4APR, Bob
>
>
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de WB4APR at amsat.org, Bob

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