[aprssig] Why do stations send telemetry parameter messages to themselves?

[John Gorkos]

inline comments

On 11/17/24 8:23 PM, Lynn W Deffenbaugh (Mr) wrote:
> Read chapter 13 of aprs101.pdf.  It describes the "On-Air Definition 
> of Telemetry Parameters" which are specially formatted messages (PARM, 
> UNIT, EQNS, BITS) sent via APRS message format packets from a station 
> to itself.   The T datatype only carries values, not the definitions 
> of how to interpret those values.

Ok.  So we have 4 specifically spec'ed, formatted messages that use no 
DTI, and cause parsers to specifically have to look beyond char[0] of an 
on-air message to see what they really contain and if they need special 
handling.  That's probably not the worst thing in the spec, but it's in 
the running...


>
> As for RXTLM-1, technically that would be an Alternate Net identifier 
> of RXTLM since it doesn't start with AP.   You can read about these on 
> Page 15 of chapter 4 in aprs101.pdf.
>
> The -1 would be a Generic APRS Digipeater Path also discussed on page 
> 15 in chapter 4 of aprs101.pdf.   The -1 would technically be the same 
> as a WIDE1-1 path.
>
> However, that said, I suspect that the RXTLM-1 is actually not meaning 
> that but is being mis-used by some software somewhere.
>
> Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32
>
>
And I still don't see the purpose of wrapping the telemetry specs in a 
message and sending it to yourself.  that triggers all kinds of 
third-party message handing in the network that doesn't need to be woke up.

I'm torn between being a spec-Nazi and just throwing my hands up and 
saying I can't fight 40 years of momentum.

>
> On 11/14/2024 4:15 PM, John Gorkos wrote:
>> I'm back into the deep, ugly guts of parsing the full APRS-IS stream, 
>> and I keep seeing messages like this:
>>
>>
>> EL-OK1BY>RXTLM-1,TCPIP,qAR,OK1BY::EL-OK1BY:UNIT.RX Erlang,TX 
>> Erlang,RXcount/10m,TXcount/10m,none1,STxxxxxx,logic
>> ER-F5ZVB>RXTLM-1,TCPIP,qAR,F5ZVB::ER-F5ZVB :UNIT.RX Erlang,TX 
>> Erlang,RXcount/10m,TXcount/10m,none1,STxxxxxx,logic
>> KI0AU-1>APMI06,TCPIP*,qAC,T2BC::KI0AU-1 
>> :UNIT.C,Pkt,Pkt,Volts,Volts,N1,N2,N3,N4,N1,N2,N3,N4
>> GM7AFE>APMI01,TCPIP*,qAS,MB7UZL::GM7AFE 
>> :UNIT.Pkt,Pkt,Pcnt,Volts,Volts,Off,On,On,On,Hi,Hi,Hi,Hi
>>
>> Why are stations wrapping telemetry parameter messages in APRS 
>> Messages and then sending them to themselves?  At least they're not 
>> asking for acknowledgements.  Can anyone explain this behavior and 
>> what it's intended to do, versus just using a :T telemetry message, 
>> per spec?
>>
>> While we're at it, what does the RXTLM-1 tocall tell me? Clearly 
>> something to do with Receive Telemetry (i.e. erlang values, etc).
>>
>>
>> Thanks de AB0OO
>> John Gorkos
>>
>>
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>
>
>
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