[aprssig] Digital two-way Radio communication in emergency situations

andrewemt andrewemt at hotmail.com
Fri Sep 5 11:08:32 CDT 2014

Well, nothing says we have to stay at 1200 baud. There have been 9600 baud amateur radio modems around for over a decade. And a parallel protocol (using a different AX.25 PID value) could be used for acknowledged messaging and log transmission (perhaps metering the log transmissions to prevent clogging the channel) while asynchronous un-acked APRS is still used for position and status reporting.

Can we go to a wider (more spectrum - eating) channel to gain baud rate? In the quoted system, there might not be voice repeaters to piggyback off, so we don't have to be constrained by their limitations.

I don't think we want to get as complex as the current cellphone network technologies;  aside from the cost and patent issues, those networks are all about centralized control and 1-hop access to that central control (which presumably wouldn't be available in the SAR environment,  or they'd just use cellphones).

Just my $.02.

Andrew, KA2DDO

-------- Original message --------
From: SARTrack Admin <info at sartrack.co.nz>
Date:09/05/2014  02:43  (GMT-05:00)
To: TAPR APRS Mailing List <aprssig at tapr.org>, sarcomm at yahoogroups.com, Search_and_Rescue_Communications at yahoogroups.com
Subject: [aprssig] Digital two-way Radio communication in emergency     situations

Hi all,

As the CEO of SARTrack Limited, and developer of the SARTrack Search and
Rescue software, I get occasionly approached by Emergency Services
organisations who basically require a full two-way *radio* based
tracking and communication system for teams in the field, in disaster
situations where all other communication networks have failed or are out
of range.

SARTrack Limited did build type-approved (non Amateur Radio) based APRS
Trackers and Digipeaters, but we no longer do this.
While the SARTrack software can transmit Operation Logs and Objects over
an APRS radio link, this is really not recommended, as the 1200 bps
radio channel is simply not fast enough for that kind of work, and APRS
is obviously not the right protocol for reliable two-way communication.

My question is this:
- What does currently exists in the area of affordable two-way, medium
speed, digital radio equipment, which can be somehow connected to a user
interface like maybe a smartphone or another device which enables
display on a screen and entering data on a (digital) keyboard?

I start to wonder if it would be possible to develop a 'commercial'
package which would make it possible to send people out in the field, on
foot or vehicle, carrying a VHF radio based system like this, and using
(portable) Digipeaters for same system to setup links to a remote base.
  There is clearly a market for this, as 'hi-speed' satellite based
systems are incredible expensive and probably more in the militairy

The radio link speed would have to be at least 9600 bps, and it should
preferably a full digital signal like PSK or QPSK or some other suitable
digital modulation type.

Any ideas and information welcome.


Bart Kindt
SARTrack Limited

SARTrack Developer and CEO
aprssig mailing list
aprssig at tapr.org
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