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Digital operation

A digital station can greatly reduce time to transmit documents in time of disaster.

A viable, portable 2m packet station may be assembled as:

  • Two-metre rig and antenna, for operation on 145.07 MHz.
  • RMS Express (free Windows download from winlink.org)
  • TNC-X or similar KISS TNC (such as MFJ-1270X). The RMS Express configuration screen lists various hardware which may be compatible.
  • Cable from TNC to rig. (These are specific to each rig manufacturer. As the rare few rigs with internal TNC's are optimised primarily for APRS, an external TNC is needed to avoid packet size limitations.)
  • Laptop PC with a low-cost printer (such as a Canon IP2700). If using a new laptop (which lacks serial ports) a USB TNC is advisable.
  • 12V-to-120VAC inverter to operate printer
  • USB memory sticks to transfer messages locally

As some configuration is required (a rig-specific TNC cable must be assembled, the software must be installed and configured in peer-to-peer mode with your callsign, Maidenhead grid square and service group - PUBLIC) it's best to have this tested and working long before it's needed for deployment.

On VHF, the 1200 bits-per-second lowest common denominator for packet radio is adequate to transmit at least a page or two of plaintext per minute. Routing messages through multiple stations (digipeaters) will lower this substantially. To save transmission time, it is best to save word processor documents to plaintext (.txt) and spreadsheets to comma-separated values (.csv) before transmission.