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[aprssig] APRS Bandwidth

Keith VE7GDH ve7gdh at rac.ca
Tue Jun 23 15:26:07 UTC 2009

Jim G0JXN wrote...

> The UK Amateur Radio license no longer allows the operation of an APRS
> digipeater without special permission (Notice of Variation) from the
> regulator (Ofcom). It being filtered first through the RSGB.

I think it's sad that the rules are so repressive in the UK when it
comes to APRS. Not just there, but it is the amateurs themselves that
should be setting most of the rules. In the UK it would be reasonable if
RSGB took on that function.

> I wish to run a digipeater on 10.151MHz (KAM) but am advised the it
> would probably not be recommended by the RSGB because the bandwidth of
> 300bd would exceed the 500Hz laid down in the IARU bandplan for 30m.
> The implication being that we should not operate APRS on 30m at all.

Regarding 500 Hz bandwidth... aren't 300 baud tones just 200 Hz apart?
I viewed the reply from Chris G4HYG (most people will probably see
it as a blank message with a text attachment) about Carson's rule...
http://en.wikipedia.org/wiki/Carson_bandwidth_rule. Doesn't that apply
to FM? See  For SSB, I would have thought the 200 Hz difference between
the two tones would set the bandwidth.

See http://www.apritch.myby.co.uk/hf.htm... yes, I see your name and
callsign at the top of the page! I agree with almost everything on the
page except the paragraph about digipeaters. There shouldn't be a need
for a digi on HF. Unlike VHF where digis are needed  to extend the
range, on HF, if there is propagation, everyone will hear whatever
activity there is in the frequency. What would be valuable would be an
IGate. A digi would just take up more airtime. Just think if a dozen HF
digis sprouted up in the UK and Europe (or hundreds around the world)
instead of everyone listening to mobile stations, they would be
listening to the digis too, and if propagation was such that a few of
them didn't hear the original beacon, they might hear the digipeated
version from the fixed station, probably with a better antenna than the
mobile station and possibly running more power. The implication should
not be to discourage APRS on 30 M, done properly with 300 baud on
SSB and not FM and well within the 500 Hz bandwidth recommended
by IARU, but that digis should not be used on HF.

73 es cul - Keith VE7GDH
"I may be lost, but I know exactly where I am!"

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