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[aprssig] Voice Alert in Europe (T136)

Geoff geoff-lists at gatwards.org
Fri Jun 4 00:04:10 UTC 2010


Bob,  

If you are updating pages, down under we use 91.5Hz (T91) for VoiceAlert
(http://www.aprs.net.au/vhf/voice-alert)

Geoff  VK2XJG


-----Original Message-----
From: aprssig-bounces at tapr.org [mailto:aprssig-bounces at tapr.org] On Behalf
Of Robert Bruninga
Sent: Thursday, 3 June 2010 11:35 PM
To: 'TAPR APRS Mailing List'
Cc: aprs at yahoogroups.com
Subject: [aprssig] Voice Alert in Europe (T136)

Seeing several references to:

>> Europe, Finland, Ireland: 144.800 MHz Voice Alert = 136.5 Hz.
>> While we've adopted 136.5 here in Ireland...

Yes, 100 Hz was fine for the USA with a 60 Hz grid and 60 Hz TV
scan rate, but in some countries in Europe, harmonics of 50 Hz
power grid and mrgawatts of 50 Hz PAL TV RF would give false
squelch openings on 100 Hz.

So for Europe, Voice Alert is 136.5 Hz CTCSS.
We need to make sure that all documents reflect this.
I just went through and corrected my web page
http://aprs.org/VoiceAlert3.html

And I invite everyone to update theirs as well.  It will take me
time to correct all of my other documents, but I will.  If
anyone disagrees that T136 is NOT the standard European Voice
Alert, lets battle it out now or forever hold your peace.

Further, Notice that in APRS we refer to tones by their
whole-number values and ignore the decimal point.  All tones
these days are generated by special chips and so we only use
their frequency as a reference, not as an exact need to specify
the exact frquency.  No one gives a hoot whether it is 136.5 or
just T136.  They dial in whatever their radio has in that slot.

That is why APRS has standardized on the 4 byte format of "Tnnn"
for specifying PL or CTCSS tones instead of CTCSS 136.5 which
takes almost 3 times as much bandwidth!

Bob, Wb4APR


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