[aprssig] APRStt (touchtone) lives

Robert Bruninga bruninga at usna.edu
Mon Apr 8 14:42:59 EDT 2019

Wow, that is good info.  Though we are kinda stuck with the way our HT’s
send their DTMF memories.  But it does suggest that making sure there are
no repeating digits might make something work at higher DTMF speed than it
would work with repeating digits.

*From:* david vanhorn <kc6ete at gmail.com>
*Sent:* Monday, April 8, 2019 2:28 PM
*To:* Robert Bruninga <bruninga at usna.edu>
*Cc:* Peter Laws N5UWY <n5uwy at arrl.net>; TAPR APRS Mailing List <
aprssig at lists.tapr.org>
*Subject:* Re: [aprssig] APRStt (touchtone) lives

FWIW:  DTMF can be sent nearly twice as fast by implementing a simple

A typical string of digits contains few repeats.

While the DTMF spec calls out 10dps as nominal speed, with 50mS tone and
50mS silent, the silent period is really not used unless you have two
digits which are the same, as 1234566789 a delay would be required between
the two "6"s.

I've used this in industrial applications very successfully.

If NextDigit = CurrentDigit, then apply delay, else not.

If you're feeling a little unlucky, a 5 or 10mS delay between dissimilar
digits can always be added but I've never seen it be necessary.

On Mon, Apr 8, 2019 at 11:05 AM Robert Bruninga <bruninga at usna.edu> wrote:

The way APRS DTMF works is that you have a 4 digit "message" code and then a
10 digit callsign so that it all fits in a DTMF memory and can be sent with
a single key press.  Yet each message is attributed to a callsign or

The 4 digit message code consists of selecting a pre-defined message (1 of
99) and then including a 2 digit "modifier"  as in "Runner 43 is down" is
0743.  I know this will not work as is for large runner numbers >99, but it
does work as is for small events with numbers under 100.  But you get the

All callsigns and station names of 6 characters or less can be accommodated
in the ten callsign digits.  The callsign part of the string is always sent
from pre-loaded DTMF memory after keying in the initial 4 digits.

So think about how we can use this capability.  Remember, almost everything
that has ever been said on ham radio has most likely already been said
before.  We just need the top 99 for any particular event template.

Bob, WB4aPR
-----Original Message-----
From: Peter Laws N5UWY <n5uwy at arrl.net>
Sent: Monday, April 8, 2019 12:49 PM
To: Robert Bruninga <bruninga at usna.edu>
Cc: aprssig at lists.tapr.org
Subject: Re: [aprssig] APRStt (touchtone) lives

On Mon, Apr 8, 2019 at 10:48 AM Robert Bruninga <bruninga at usna.edu> wrote:

> 1.  Runner XX just passed
> 2.  Female XX just passed
> 3.  Handicapped XX just passed
> 4.  EMS is on scene
> 5.  Need more water
> 6.  Need checkpoint captain
> 7.  Runner XX is down
> 8.  Need EMS
> 9.  Am at checkpoint XX
> 10. ....?

If reporting a runner's sex is really needed, can't you just add and M or F
flag (or H for disabled runner ... maybe Y for runner under some age that
means something)?  Dunno - not a marathon volunteer (or runner!).

When is the launch expected?  (and yes, I know what the date means - "no
earlier than")

Peter Laws | N5UWY | plaws plaws net | Travel by Train!

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