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[aprssig] APRS Voice Alert

Dave Baxter dave at emv.co.uk
Wed Sep 7 08:59:08 UTC 2005


ALL of the AC power in Europe is 50Hz (with the posible exception of a
few US military sites) as it is in much of the world outside the
America's.  Some of the middle & far east (US influence after WW2) use
60Hz, but most use 50Hz.  Japan has both 50 and 60Hz, often in the same
street!

It's highly unlikely any 50Hz power line interference will falsely
trigger a rig listening for a 100Hz pilot or CTCSS tone.  If it does,
the power supply feeding the rig will almost certainly be to blame
(faulty) or it's not up to the job (overloaded).

Though 100Hz does appear in some menus, I don't even think it's used
within the 50Hz power area, for the very reason that it "could" be
triggered by a faulty system.

Also please note, on 2m in the UK at least, we use 2.5kHz deviation for
FM-Voice, and 12.5kHz channel spacing.  Packet/APRS still seems to use
5kHz settings, but with the audio drive reduced to keep the FM sidebands
down.  But, as a result the radios have 25kHz channel spacing filters in
line.  Any voice activity on any packet/APRS channel in the UK would
therefore affect the two adjacent frequencies.  Another reason why it
would be very unpopular hear!

I would somehow expect anyone visiting who tried to use voice alert, to
not get very far, other than "receiving some grief" from the locals if
they tried "calling" using that facility within the 144.800 area.

Also note.  Our allocation is from 144 to 146MHz.  2MHz band only, so we
have even less spectrum space to spread out into.   Don't even think of
trying 144.390 for APRS, (a) it wont work, (b) you'll get no sympathy
from the DX beacon watchers.

As you well know.  APRS is a semi automated digital communication
system.  Why mess with it by advocating the use of voice on the same
frequency as well, even if just for "calling"?  If the operator is
about, they would respond to an APRS message just as well if able.  For
calling drivers, they then have the hassle of QSY'ing, and killing the
APRS function before talking, and doing all that in reverse after the
chat.  When driving a vehicle, that is unacceptable, and there are fewer
and fewer places to safely pull over and stop for a minute ot two.

On a separate "net" frequency for special purposes (events or emergency
coordination) I do see advantages, perhaps in conjunction with Mic-E
use.  But on a national data frequency, I think that is unacceptable,
and will only add to confusion.

End of topic I think...

Dave B.  G0WBX.



> -----Original Message-----
> From: aprssig-bounces at lists.tapr.org 
> [mailto:aprssig-bounces at lists.tapr.org] On Behalf Of Robert Bruninga
> Sent: Tuesday, September 06, 2005 8:17 PM
> To: aprssig at lists.tapr.org
> Subject: Re: [aprssig] APRS Voice Alert
> 
> One problem with Voice Alert in Europe is that I'm not sure 
> what tone they use.
> 
> We use 100 Hz here in the USA, but since many of the AC Power 
> Grid in Europe is at 50 Hz, this make PL 100 practically 
> useless in Europe.  I have seen references to maybe
> 136.5 Hz, but then I have also made the mistake of writing 
> 123 Hz sometimes.  And of course, unless everyone uses the 
> same tone on the same continent, then it really doesn't work 
> for its intended purpose.
> 
> So, if anyone on this list uses APRS Voice Alert in Europe, 
> tell us what tone they use.
> thanks
> 
> 
> Bob
> 
> 
> 
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