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[aprssig] APRS Voice Alert

Steve Huston huston at astro.princeton.edu
Fri Sep 9 10:18:39 UTC 2005


On Sep 08, 2005, at 22:20, A.J. Farmer (AJ3U) wrote:
> On 9/8/05, Wes Johnston <aprs at kd4rdb.com> wrote:
>> A.J. Farmer (AJ3U) wrote:
>>> You don't need a TNC to "hear" the packet.  This is just a PL/CTCSS
>>> function, it has nothing to do with a TNC.  All you need is your
>>> receiver tuned to 144.39 with a CTCSS of 100.  All of the  
>>> transmitters
>>> that are transmitting normally without a PL of 100 will be muted by
>>> your receiver so your your receiver will be silent the majority  
>>> of the
>>> time.  The only time you will hear packet bursts is if a transmitter
>>> is within simplex range and is transmitting with a PL of 100.
>> Careful there.... your TNC needs to hear enough to know when the  
>> channel
>> is in use so as not to TX.
>> No TNC on a 2nd receiver in the car is a good solution though.
> I was referring to being able to receive voice alert packets, not
> transmit.  I thought that was what he was asking.

Sorry, I should not try to post things when I'm half asleep :>

I already have a dual-band radio in the truck, and would want to add  
a 2m rig for APRS (with various other goodies attached, which I  
mentioned here before - and Curt, WE7U gave me some great ideas for  
that too!)  This radio would therefore want to transmit and listen on  
39, not only to handle APRS packets in both directions but also to  
let me know when someone is nearby.  Currently I have a memory  
location set with the PL, as A.J. suggested, so I'll know if an APRS  
user is nearby even though I'm not decoding any of the packets.

So I'm not tying up the radio on another frequency, I figured the  
best bet was to hook the TNC to the APRS rig in such a way that even  
if there's no PL on frequency, it'll still hear all the traffic for  
decoding ("discriminator output" is the phrase I was looking for, but  
see earlier mention of posting while asleep) but will be able to  
squawk the packet out loud when the tone exists so I know someone's  
nearby.

I'm also thinking of wiring up either a digital playback unit of some  
sort, or if I go with a computer for APRS functionality a soundcard- 
type hookup to the APRS rig, so that with the push of a button a pre- 
recorded sound bite can say "W2SRH listening on 146.52" or something  
similar - now I wouldn't need to keep a mic connected to the radio  
either, but will still be able to do voice alerts with the greatest  
of ease.  But I'll worry about that part later on.

--
Steve Huston - W2SRH - Unix Sysadmin, Dept. of Astrophysical Sciences
  Princeton University  |     ICBM Address: 40.346525   -74.651285
    126 Peyton Hall     |"On my ship, the Rocinante, wheeling through
  Princeton, NJ   08544 | the galaxies; headed for the heart of Cygnus,
    (609) 258-7375      | headlong into mystery."  -Rush, 'Cygnus X-1'






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