A Wide-Range Beacon/Bulletin Alternative
Message posted by W7ASA for KB1TCE
A fellow TAPRN member posed the question: “What would be a good way to
transmit brief alert messages or updates on a repetitive basis?”
Ideally this would be some kind of automated system that sends out a
status at regular intervals, thereby compensating for variations in
propagation and listening hours.
After discussing a number of possibilities and doing some on-air
testing, a few of us came to a general agreement that leveraging the HF
APRS system would provide a good solution.
Most hams are familiar with VHF APRS, used for tracking, search and
rescue, weather data reporting, simple messaging, etc. VHF, of course,
has limited range and is dependent upon digipeaters and the internet for
distance operation. Not what we’d want.
HF APRS by definition has much broader coverage. Like its VHF
counterpart, it can use the internet infrastructure via stations that
are tied to the internet (I-Gates). Also, like VHF APRS, HF APRS uses
common frequencies and it’s OK to run full auto, beaconing every 20-30
minutes. Signals might collide every now and then but the usage is low
enough that most transmissions will be in the clear.
The standard worldwide HF APRS band is 30 meters. Stations work with HF
packet and several sound card modes. For PSK and MFSK modes the center
frequency is 10,149.7 MHZ and the dial frequency is 10,147.6 USB (2100
Hz waterfall).
Two types of messages can be sent. The first is a periodic beacon that
includes the station call, specific or generalized lat/long info and
some text. The second is a message (67 characters max) that can be
addressed to a specific station call or to a group name.
To use HF APRS you need some software. The one that is applicable is
APRS Messenger, developed by Chris Moulding, G4HYG. It’s freeware and is
available for download at
http://www.crosscountrywireless.net/aprs_messenger.htm
There are no restrictions on who can download the program so non-hams
can use it for monitoring. A detailed description for set up is
available from http://wa8lmf.net/APRS_PSK63/.
For testing purposes, we have been sending messages to the group TAPRN.
(The group name can be anything up to 6 letters.) Here is an example,
pulled off of http://aprs.fi/?c=message&call=TAPRN
2012-07-31 01:18:03 UTC: KB1TCE-63>TAPRN: One active survey (water)
The message would probably be meaningless except for anyone who is
active on the BBS network and is aware that there are regular bulletins
and surveys. The person who is monitoring messages can either let his
radio listen when convenient or just go to the aprs.fi web site,
assuming that there is internet access.
>From Maine, the best 30 meter propagation (based on I-Gate hits) seems
to be in the late evening and early AM hours. That’s great as I could
just set my rig to transmit during those hours, given normal
circumstances. Just key in a message and let it run while I sleep.
We would really appreciate comments on this, including suggestions for
specific alert protocols or even better ideas.
Date: August 23, 2012
