Lake Hume Amateur Radio Group

APRS for public safety at a mountainous event

By Phil VK2CPR

Members of the Lake Hume Amateur Radio Group (LHARG) constructed a portable Automatic Packet Reporting System (APRS) command station and digipeater at the Mt. Bogong ‘conquestithon’.  The conquestithon, held in early March 2016, is organised and staffed by members of the Upper Kiewa Valley Lions Club. The event started from the Mountain Creek picnic area at the base of Mount Bogong to encompasses a 20km round trip with a climb of 1,300 meters to the summit of Victoria’s highest mountain. LHARG normally provide a portable voice repeater for communication with check-points around the course.

The challenge for this event was to track the race ‘sweep’ and other officials in difficult and mountainous terrain. The plan was simple enough on paper; we planned to track people through deep valleys and lofty summits during the event, all independent of the internet. A portable digipeater on a ridge reported to a base control in the Mountain Creek valley campground which placed people on a specially constructed map of the area. Members camped overnight at Mountain Creek ready for the next day.

group shot

Tea at Mountain Creek camp ground with (left to right) Peter VK2CIM, Riley, Shane VK3KHS and Stafford VK2AST

We employed a portable APRS digi on 145.175 which was situated across the valley facing the course. One of the aims was to place the digi (VK2AHA-1) in a position so it could be heard by the wider network and at the same time ‘see’ into the mountain creek valley. An optimum position was found on the ridge line and our stations became visible on the  global system.

We found that there was a 300 meter stretch of track on the ridge line which could be heard by the wider APRS network and mobiles on the course.

APRS bogong digi test

The ridge line ‘sweet spot’ optimum positioning points for the digi to the wider APRS network

Stafford (VK2AST) and Phil (VK2CPR) constructed three Argent OT3 mini APRS units for the officials. The units act as digis in their own right and provided a moving ‘network’ of connectivity over the entire course. The OT3s provide a telemetry output which updates ‘real-time’ battery voltage and temperature. Phil constructed the VK2AHA-1 digi on the ridge line from an old Paccomm Micro 2 packet controller powered by a newly burnt UIDIGI[1] EPROM. The digi was interfaced to an ‘Any Tone’ 588 2 meter rig.

vk2aha-1 APRS

The position of VK2AHA-1 across the valley

The base platform at Mountain Creek was constructed from an Apple Macbook running Oracle’s Virtual Box (VB)[2] free emulation software. The APRS software included the UI-view[3] mapping software, UZ7HO[4] sound modem and a home brew interface to a hand held. UI-view maps of the area were constructed from various maps including a detailed Country Fire Authority (CFA) Map. The base antenna was just a simple home-brew collinear.


The base APRS platform at Mountain Creek camp ground

We checked three levels on the course before the race. Shane (VK3KHS) drove along the upper ridge line, Phil (VK2CPR) 4WD’d in the valley along Mountain Creek and Peter (VK2CIM) was the hardy soul who volunteered to climb the mountain. Peter constructed an APRS back pack containing a Yaesu Vx-8, an MFJ310s window mount to which a Diamond SRH 779 antenna was attached.


Peter VK2CIM preparing to ascend Mt. Bogong

Peter was tracked by the digi until he reached sufficient height on Mt. Bogong to be heard in the wider network.The digi successfully relayed positions from all of the participants to the base map as they progressed along the deep valley, high ridge line and the ascent of the mountain. The day was a success with all of the gear running as expected and many valuable lessons were learnt.

Members of LHARG suggested that APRS could be a valuable safety network for public events, or searches, in this wild and challenging terrain.