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[aprssig] Text Messaging Radios (a simple use)

Robert Bruninga bruninga at usna.edu
Thu Feb 12 18:39:45 UTC 2009


Using DTMF memories to check into a net
On an alternate back-channel to net control:

> 999*277#PRI#
> 
> I liked the proposal until I got to the 
> call sign part.  If "277" shows up on my 
> screen, I would need to look at a cheat-
> sheet to figure out who it is.

Good idea.  I modified it to this for my
DTMF memory number 1:

999*277#APR 1#

So now what the net control sees on his radio is my numeric ID
and my Callsign suffix and instead of the 3 letter abbreviations
for the urgency, it's a digit between 1 and 3.   He will see
this: (if your email displays fixed font)

+------------+  where 146.94 is the band B on this radio
|p277 146.940|  where "277" is the ID for "APR"
+------------+  where the "p" shows it was a page
| A P R   1  |  where "A P R" is my alpha suffix
+------------+  where I have priority 1 traffic

But for a special event, a cheat sheet would be handy to have in
any well planned event.  But even if I don't have it, the net
control could call "ID 277 call now" and the ham would make his
call and sign as "number 277, WB4APR" like we do with any
tactical calls at events.

> There are 27 different call suffixes that 
> map to that 3 digit number... 

Even if two were at the same event, the ambiguity would cause
little problems in this application.  The person sending the
text would know that the reesponse was for him.
There are already so many ambiguities in callsigns that "sound"
alike that I don't think this would be any worse.  The net would
call "Number 277 call now" and the 277 that had indicated he had
traffic would respond.

> Perhaps you'd be better off just assigning ordinal 
> (tactical?) numbers to the operators (maybe even have the 
> number on their jersey, athlete-style, so you could locate 
> them quickly), or figure out a way to map letters to multiple 
> digits (pairs) so that they can be displayed and read.  Do 
> any of the radios have an alphanumeric display capability?

Yes, ordnal numbers would work too.  But ALPHA-numeric display
is the whole point of this discussion.  The text paging radios
we have identified are the FT11,41,51 and TH78 and there maybe
close to 100,000 of them out there.  And all you have to come up
with is ONE for the whole event to put in front of Net control.
(or anyone else handling lots of incoming traffic).  Because
then anyone with any HT can send to them from their DTMF memory
or directly from the keypad.

> If they don't have anything built-in, you'd 
> need a DTMF decoder plugged into Net Control's 
> rig.

Yes, if this catches on, I am sure that Byonics, OpenTrack of
HAMHUD would find it useful to add the DTMF decoder to their
displays.  The real advantage is being able to include 100% of
every volunteer at your event in the ability to send simple text
data to net control.

Find someone with one of these radios in your area (charge it
up) and experiment...

Bob, WB4APR




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