[aprssig] APRS Telemetry Question
hessu at hes.iki.fi
Fri Oct 12 13:45:58 CDT 2012
On Fri, 12 Oct 2012, Steve Noskowicz wrote:
> With these radios we can send what I call a "standard APRS text
> message" via the knob-twiddle method or an added keyboard/W2FS-adapter.
Ok, that's just a text message. You can't put telemetry data there.
You can use it to transmit the coefficients and parameter names, though.
> All the data in "telemetry messages" is ASCII, so... My intent of this
> question is to determine whether the D700/D7 radios can send a telemetry
Can send parameter names ("Channel is Temperature") within a text message.
Cannot send telemetry data ("Current temperature is 10").
> Q: One way to re-word this question is: If, on a D700, I send a
> message via the knob-twiddle method that starts with T#001, then comma
> sep groups of 3 ASCII digits, would it be interpreted as Telemetry?
> OR, is there some other "sfuff" in a "true" Telemetry packet that
> distinguishes it as Telemetry and NOT an ordinary message? - OTHER than
> the fsct that the message is 'to itself".?
Telemetry looks like this in the raw packets:
2012-10-12 10:13:37 UTC:
A text message looks like this:
2012-10-09 06:47:56 UTC:
Note that the first : after the packet path is just a separator character
to separate path and the packet's data. The second : in the above text
message is actually within the packet's data portion, and it tells us it's
going to be a text message, and the recipient callsign follows that.
> Q: Is the "#" required or optional?
> Q: I also see that KI6TSF-8 has only 2 characters in the sequence
> numbers, so aparently the telemetry sequence number length is not fixed,
> and possibly ignored anyway...no?
Depends on the recipient, but it shouldn't be completely ignored - it
should be used to drop old packets which arrive out of order.
> APRS 101 mentions bulletins....making this confusing.
APRS101.pdf can be confusing at times, I can agree with that. :)
Bulletins are actually sent using the same format as text messages, they
only have BLN as the first three characters of the recipient callsign.
Compare http://aprs.fi/bulletin/ with the raw packets of the stations
More information about the aprssig