[aprssig] APRS-SIG (... proposal for a world wide APRS net on 20m?)
dave at uk-ar.co.uk
Thu Jun 25 08:23:14 CDT 2009
Hi Jim (and others)...
There is already ALE or HFN. A world wide automated HF digital
messaging system, primarily for emergency use, it's there and working.
With the ability to negotiate a link for voice too (SSB)
http://www.hflink.com/ It also has some APRS like position reporting
However, our licence limitations don't make that mode easy to deploy
either, hence the lack of G (or M) stations active in this mode.
20m is congested enough as it is on most weekends (contests etc.) I
suspect a proliferation of APRS would not exactly be welcome, even if a
compatible slot for it could be found.
I understand your concerns re 30m APRS, and it is useful on occasions.
However, the problem with digi's is they dramatically increase the
loading on a single channel of course, and at 300bd, that's already 4
times as long (timewise) for a typical packet as at VHF. Unless there
could be some (internet based?) liaison between any such digis so that
one and only one digi'd what was heard.
But then, what happens when the i'net liaison link dies for whatever
30m iGates: If correctly setup, so as not to spew stuff out to RF, only
messages to those in direct earshot, maybe, and only maybe that could
work. But again reliance on a service that we have no control of in the
background. The Inernet (not the APRS-IS) of course.
Then there is that old chestnut, that FSK is not exactly spectrum
efficient these days, compared to other choices of digital modulation
available to us.
Dave G0WBX. Stirring it as usual.
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