[aprssig] Proposal for APRS12 spec fix - Telemetry should allow for 000-999

Robert Bruninga bruninga at usna.edu
Tue Apr 28 15:51:21 EDT 2020

The original APRS spec said that the 5 channel
T#sss,111,222,333,444,555,11111111 telemetry format would be limited to 5
channels from 000 to 255.  But in fact, many people have been using values
from 000 to 999 without affecting the fixed 3 byte format.   The only reason
for the original limitation was simply that that was what was being
transmitted by some early TNC's..

I see no need to not allow 000-999 in those fields for the more common these
days  10 bit A/D telemetry sensors, since it does not change the 3X fixed
integer format.

So I propose to document this note in the APRS12 update page:


-----Original Message-----
From: Pete Loveall AE5PL <pete at ae5pl.net>
Sent: Tuesday, April 28, 2020 2:36 PM
To: Robert Bruninga <bruninga at usna.edu>
Subject: RE: Telemetry should allow for 000-999

Actually, Bob, it was not arbitrary.  That 3 digit value represents 1
unsigned byte because Kantronics (and the rest of the experimenters in the
1990s) used 8 bit A-D converters (thus, also, the term "analog" when
referring to those values).  Any software that supports the spec might be
backing it with a single byte value.

javAPRSSrvr is unaffected by that aspect of spec and its server operations
(passing packets) is -not- affected by that aspect of the spec.  I wrote
APRSFilter, however, to be specification specific and it does not consider
non-compliant packets as being "ok".  Again, this does not affect
javAPRSSrvr's operation as an APRS-IS server.  It only affects those who try
to use a telemetry filter on a flow restricted port.  If it is of
significant concern, use the callsign filter for the station of interest
sending the telemetry and those packets will be passed along with any other
packets -generated- by the requested station.


Pete Loveall AE5PL

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-----Original Message-----
From: Robert Bruninga <bruninga at usna.edu>
Sent: Tuesday, April 28, 2020 1:09 PM
To: Pete Loveall AE5PL Lists <hamlists at ametx.com>
Cc: Robert Bruninga <bruninga at usna.edu>
Subject: Telemetry should allow for 000-999


Can you change the test in APRSSrvr for the 255 limit in the telemetry to be
0-999 and not just 0-255.  That was an arbitrary limit since the original
MicE from TAPR only transmitted 0-255, but there should never have neen a
restriction on receipt of 000-999 since the goal was a fixed 3 digit integer
field and since most A/D telemetry boxes now use 10 bit A/D converters, this
restriction is obsolete.

In fact all my satellites have used the broader field for years.

If you like, I can change the spec in APRS12…



From: Lynn W. Deffenbaugh (Mr) <ldeffenb at homeside.to
<mailto:ldeffenb at homeside.to> >
Sent: Monday, April 27, 2020 10:30 AM
To: Robert Bruninga <bruninga at usna.edu <mailto:bruninga at usna.edu> >
Subject: Re: [APRSISCE] JS8CAll/FT8 Log Scrapers (Dev 2020/04/26 22:23)

Actually, I "fixed" it because javAPRSSrvr is very strict when it comes the
spec compliance.  The t/t (type of telemetry) filter does not consider
telemetry packets with values >255 to be telemetry and it won't pass them on
that filter.  As long as the packet matches some other filter, it will pass,
and the packets certainly propagate through the APRS-IS network, but
javAPRSSrvr doesn't consider them to be telemetry.

Lynn (D) - KJ4ERJ

On 4/27/2020 10:19 AM, Robert Bruninga wrote:

	 I have no objection to telemetry in the 5 channel format  to be 000-999.
I use that on all  my satellites.There was no reason to limit it to 0-255 as
in the original spec.


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