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[aprssig] APRS Voice Alert for Travelers

Bob Bruninga bruninga at usna.edu
Wed Nov 24 13:38:09 UTC 2004


On this peak travel day, there is something Better than 52.
APRS Voice Alert.

If you're on a long trip and cant find anyone to talk to just activate
your mobile HAM "radar" detector.  Many APRS mobiles run what is called
"voice alert" on 144.39 MHz.  This means they are LISTENING with CTCSS
100.  Thus, they never hear anything unless someone is within SIMPLEX
range of them and calls with CTCSS-100..  Its like a radar detector.  If
you pass within simplex range of someone else with VOICE-ALERT, even if
they are not talking, you will hear an occassional ping because their once
a minute packet is also transmitted with CTCSS-100. (136.5 europe).

Even if you dont run APRS, but just want to see if anyone
is in simplex range while driving, anyone can tune there and listen.
If you hear a packet break your CTCSS 100 squelch, then you know he
is in SIMPLEX range and he is also LISTENING on the speaker for a call
with PL 100.

This is better than 146.52, because of the automatic "pings" by each such
mobile.  You can drive all day listening to 52 and pass within range of
dozens of others, but if no one calls CQ once every two mintues or so, you
may never find each other. (Two cars passing at 60 MPH are beyond mobile
range in 5 minutes.

With APRS Voice Alert you have three guarantees:
1) One of his radios is ALWAYS ON.
2) One of his radios is ALWAYS tuned to  144.39
3) If he has set VOICE ALERT, then he has the VOLUME UP and
   will hear you if you set CTCSS-100.

But if you call on 144.39 voice alert, you MUST state "calling on Voice
Alert", otherwise, he will assume you came in on his normal voice radio
and he will come back to you, but on the other radio because he has no way
of knowing otherwise.

Note also that you must set CTCSS 100, or you will be driven crazy by all
the packets.  Remember, VOICE ALERT is only a CALLING channel. You must
immediately QSY to a voice channel for QSO.  144.39 is a packet channel
only.  This Voice Alert process is only a convenience for mobile
operators.

NOTE, Never set PL 100 from a fixed APRS station.  No one wants to hear
your pings unless you are STITTING THERE ACTIVELY looking for a QSO.  In a
mobile, if the APRS rig is on, he is there and his volume is up and he is
listing.  Thus VOICE-ALERT is considered to be a "live" process only.

de WB4APR at amsat.org, Bob






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