APRS Voice Alert
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Updated 26/04/2007

APRS Voice Alert

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Origination of the Concept

Actually, what started VoiceAlert was the frustration of driving down the road, out in the middle of nowhere and seeing a passing APRS tracker and having no means whatsoever to contact him.

Same goes for looking at a mobile on a map in the middle of the emergency operation, right where you might need a mobile and having no way to know how to contact him.

I have nothing against trackers. They are very valuable in controlled events where you have a COMM plan and know how to contact them or what their frequency is. But the other 99.9% of the time, they may as well be moving fence posts. <grin>. As far as 2-way comms is concerned that is...

 

Informal Description

Question; I've read the TH-D7A manual several times and not seen anything about any Voice Alert.

Answer; "Voice Alert" is not a Japanese invented setting. It is a term we use to describe the simple APRS action of: 

1) Leave your D7/D700 APRS volume turned up.

2) Use a CTCSS tone of 91.5Hz to mute the APRS speaker instead.

That is all there is to it. What this gives you is the added capabilities of:

 

bulletBeing able to HEAR someone who has an immediate need to contact you. Because everyone can see that your APRS radio is on the national APRS channel.
bulletTags your packets with PL/CTCSS 91.5Hz so that others that are listening will be aware of your presence -AND- know that you are listening. 
3) Because you will hear PL91.5 packets, it alerts you to the presence of another so-equipped mobile who you also then -know- he is listening.

4)  Lets you raise that person by voice and QSY as easily as pushing your PTT.

Question; The D700 is also popular [but higher] cost.

Answer; Yes, so why not take full advantage of these dual band radios by -not- turning the volume down on half of it, but setting CTCSS to mute the speaker on the APRS side instead. This way, you have APRS, and you have the Band B for all other voice uses... PLUS you get a speaker on a single national frequency that can be activated within simplex range by anyone that has an immediate need to contact you.

 

Rig Independent

VoiceAlert is rig independent. You don't need a D700, nor do you need to even run APRS. All you need is a radio that will do tone squelch.

Just put 145.175Mhz with a CTCSS tone of 91.5Hz in the scan list of your mobile rig. If you hear a packet burst, then you know an APRS VoiceAlert station is within simplex range.

 

Examples of Voice Alert applications.

Laugh With Me

RE: yacking on Voice Alert... a.k.a. please laugh _WITH_ me.

Background:

36 year Electrical Engineer in communication field with _major_ 2-way manuf. Know all about RF, audio, PL etc. In fact, designed much in each area. Fast forward to around 2002 and the acquisition of a D700 & GPS. Read all I can and get it set up, including what you now call Voice Alert. I read about being able to give short calls and be heard - neat idea. Now I know enough to call and get off, so I don't think "most" hams would QSO on .39, but that's only my opinion and you never can under estimate the stupidity of come (stand by please...).

Now. You'd think that I filled in all the blanks here, but as time goes on I keep hearing these APRS "Sqwaks" as I call them. It isn't all the time, just once in a while... Sheesh, I'm thinkin' How could Kenwood let this kind of a flaw happen? Letting APRS bursts through a PL squelched receiver. Perhaps I should call them and see if this was fixed on later models (I have one pre-owned). Gladly, I didn't. Then one day, I'm talking to Robie, WA9INF and he mentions something about the 123 PL Voice Alert and BONG! Of course you idiot, I think to myself. You'll not only hear voice, but also _beacons_ of near near-by mobiles with the PL on. DUH!.

Tail between legs, 73, Steve, K9DCI

Private Voice Alert

If you have a fixed station and want to have an ALWAYS-ON monitoring channel for VOICE calls, just use your APRS station with a PL other than 91.5Hz. I'll call this PRIVATE VoiceAlert.

My kids (both licensed) were locked out of the building and were unable to raise me, because I had no monitor on in the office (though I do have APRS running all the time). Duh... I should turn the volume up and set CTCSS! Then they can raise me on 144.900Mhz if needed using my unique PL.

PLEASE never operate fixed station on PL91.5 voice alert! It drives mobile voice alert stations crazy. But until now, I had not realized that I could have the same advantage in my office while not bothering others by simply choosing my own "unique" CTCSS on 144.900Mhz. Then you can put that in your POSITION text so that others needing to raise you can see what it is.

My STATUS text might say. At work. PL107

or something like that... 

Modified for VK. Original article by WB4APR, Bob 
 
Traveling on the Road.
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 145.175 MHz.  This means they are LISTENING with CTCSS
91.5.  Thus, they never hear anything unless someone is within SIMPLEX
range of them and calls with CTCSS-91.5..  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 occasional ping because their once
a minute packet is also transmitted with CTCSS-91.5.

Even if you don't 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 91.5 squelch, then you know he
is in SIMPLEX range and he is also LISTENING on the speaker for a call
with PL 91.5.

This is better than 146.5, 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 minutes 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  145.175MHz
3) If he has set VOICE ALERT, then he has the VOLUME UP and
   will hear you if you set CTCSS-91.5.

But if you call on 145.175 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 91.5, 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.  145.175 is a packet channel
only.  This Voice Alert process is only a convenience for mobile
operators.

NOTE, Never set PL 91.5 from a fixed APRS station.  No one wants to hear
your pings unless you are SITTING 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.

Modified for VK. Original article by WB4APR, Bob