The Amateur Packet Reporting System APRS - is a digital technology based in packet radio, but automatically relaying its messages. Unlike conventional packet it thrives in either a VHF, UHF or HF environment virtually in real time, using digipeaters.
APRS displays a map on a computer screen, showing the location of each transmitting station it hears. This can include all kinds of moving stations land mobiles, boats, aircraft; even the Space Shuttle.
The icon moves across the map as the mobile progresses. if the transmitting station sends a text message, those receiving the signal can read the text by clicking the icon. The map can be "zoomed" to show any desired piece of real estate, from the whole country to a few square blocks in a city or the streets of the smallest towns.
Since the signals are "digipeated" i.e., automatically passed along to distant digipeaters (digital repeating stations) and other receiving stations an APRS net can cover large geographic areas. If these areas overlap coverage of, say, an HF emergency net APRS can be a useful back-channel for the net filling gaps caused by the vagaries of HF propagation. APRS can run in parallel both with regional VHF nets and Section-wide HF nets, covering portions of the same geography at the same time. This allows GATEway operators on NFEN, for example, to communicate directly with each other via APRS without disturbing the HF operation. No net control is required for APRS.
When APRS and voice nets run in parallel (overlapping some of the same geographic coverage), the voice NCS can easily monitor APRS visually at his operating position as the voice net proceeds. If NCS does not have APRS capability, he can designate an APRS-equipped station to relay information to the voice net as appropriate.
APRS is especially useful in real-time severe weather reporting. As each station reports its weather, its icon pops upon the map on the APRS receiver at the National Weather Service, and its weather data can be extracted by the click of a mouse. Wide geographic distribution provides an excellent idea of the extent of the weather being reported.
Operation of the digital system is nearly invisible to most ARES operators, but it can also handle heavy loads of Routine and Welfare message traffic from NTS without loading the voice and CW nets, and without attracting a crowd of voice operators looking for a direct contact with some station in the devastated area.
Currently, two known HF digital links are available within the section.
The first is the HF Packet Gateway operated by the Anchorage ARC on 80 meters. It is widely accepted within the amateur community that HF packet is a relatively inefficient mode of communications. While it is noted that multiple connects can be made on the same frequency, throughput on HF packet is marginal at best. Currently, activity on this link is extremely low. It is improbable that more than a single connect would need to be maintained by the Anchorage system at any one time, even during an emergency. The benefits of simultaneous connection can easily be outweighed by the throughput provided by Pactor. it is recommended that if this station is to be maintained, that the mode be switched to either Pactor or Pactor II.
The second HF digital link currently in operation is the WinLink HF Pactor Gateway operated by AL7PI in anchorage. This station is frequency agile and maintains regular schedules with five stations in the lower 48. The system automatically selects the best band for communications. Traffic bound for the lower 48 via the NTS system or for email delivery can be delivered to AL7PI's system via VHF packet. The system will then auto-connect to one of the five stations in the lower 48 and forward the traffic. Traffic bound for Alaska from the lower 48 is also delivered in a similar fashion. It is recommended that key areas within the Alaska section install WinLink HF Pactor Gateways similar to AL7PI's system to effect HF digital communications.
9600 baud PacSat communications has proven its capabilities over the years. A number of satellites support this mode and provide many communications windows each day in which traffic can be moved within and outside the section on a timely basis. In years past, the Anchorage ARC had sponsored such a system. It is recommended that key areas within the Alaska section install PacSat stations to effect communications within and outside the section.