[aprssig] APRS Telemetry Question

Heikki Hannikainen hessu at hes.iki.fi
Fri Oct 12 01:12:39 EDT 2012

On Thu, 11 Oct 2012, Steve Noskowicz wrote:

> Q:  Is Telemetry a standard APRS message?
>  If telemetry is a standard APRS message/bulletin, then the D700 and D7 can send telemetry (I know how to send messages with a computer into the radio's serial port).

Well, it's a standard APRS message / packet (that's a slightly ambiquous 
wording), but telemetry data is not transmitted in a TEXT message or 
bulletin. It's an APRS packet type of it's own, starts with a T# (text 
messages start with a ':').

On the other hand, telemetry channel names and coefficients are sent in 
APRS text messages - the destination callsign specifies the telemetry 
station whose parameters those are!

>  I don't see all four descriptive message types (no bulletins - UNITS, EQN, BITS) in the raw data on findu - that I can decypher.
> I do see:
>   [  KI6TSF-8>APOTRS,N6ZX-3*,WIDE1*,qAR,W6PKT-5:_01010000c...s...g...t073h50X221  ]

That one is a weather packet.

If you wish to see what each packet decodes to, use the decoded mode of 
aprs.fi's raw packets display:


There's a switch between Normal / Hex / Decoded at the top of the view. 
That particular station is transmitting telemetry (just one temperature 
channel), and it's also sending channel name & coefficient information, 
do a CTRL-F (find) for telemetry-message on that page to see those.

> Q:  Are the four descriptive messages bulletins or messages?

The parameters (EQNS, PARM, UNIT, BITS) are transmitted in APRS text 
messages as the text message content.

> Q:  Are the four descriptive messages a once a day type of thing (101 doesn't say)?

Something like that - there isn't a standard saying how often the 
parameters should be sent. Some send them every few hours, at startup, or 
once a year (by hand). Depends on what you need. I'm not sure if mobiles 
decode these commonly, so transmitting every 10 or 20 minutes would 
probably be too much.

   - Hessu

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