Central Ohio Traffic Net (COTN) will be experimenting with the passing of digital traffic. This is not to be confused with the National Traffic System Digital (NTSD), which is an all-digital parallel system to NTS. This is moving traffic from one COTN station to another in a digital mode. WB8NUT has some excellent information on digital modes, and will help you to understand why there are so many modes and when one mode should be used instead of another.
I strongly encourage any station wishing to pass traffic digitally to practice before the SET. I am happy to practice with anyone interested.
We'll be passing radiograms during the 2015 Simulated Emergency Test (SET). The most straightforward option for getting this to work will be to use the open-source software fldigi and its related flmsg, which will automatically put received traffic into the proper form for display.
We'll be using the MT63-2000LG mode for any transfer. Your software might instead label the mode as MT63-2k long or some variant. of that. The critical components are MT63 which is the mode, 2000 which is the bandwidth (in Hz), and long which is the error correcting code. If you have those three items set no matter whether you're using fldigi or something else, it should be compatible.
The Central Ohio Radio Club (CORC) has asked us to use the 147.330 repeater for passing digital traffic. We may also use simplex frequencies, and may do so as events warrant. Some sessions are scheduled as simplex sessions, and in others we might be operating on the 147.330 repeater. In either case, a net control will direct stations to a simplex frequency for the exchange of traffic.
We'll mention how to check into the net as digital transfer capable, how net control will direct the exchange of digital messages, how stations will exchange the traffic, and how to return to the net.
When checking in capable of receiving digital radiograms with MT63-2000LG, add "/D" to your callsign. For example, if you got your license in 2011 or after, you're running on emergency power, and you're capable of digital message exchange, you'll announce like
Kilo Delta Eight Tango Tango Echo Stroke Echo Stroke Delta New Ham
Net control will record you as KD8TTE/E/D and make appropriate use of your capability and report as such.
Net Control Directing Digital Exchange
When two stations should transfer traffic and are both digital capable, net control will direct them to go to a frequency appropriate for the exchange. This both speeds up the transfer of traffic and prevents stations on the net from hearing digital data transfer on a frequency that is primarily used for voice. For example, if KD8TVB is net control and wants KD8TTE and KD8TQI to exchange digital traffic, the exchange may go something like this:
KD8TVB: KD8TTE, go to 147.330 to receive one digital for Bexley from KD8TQI.
KD8TVB: KD8TQI, go to 147.330 to send one digital for Bexley to KD8TTE.
Net control now records that both stations are off frequency and will continue to conduct the net, waiting for those stations to announce their return before recording the traffic as passed.
Exchange of Digital Traffic
KD8TTE will go to 147.330 as directed by net control and see if the frequency is clear for the exchange.
Is the frequency clear? KD8TTE.
After hearing nothing, KD8TTE will determine that the frequency is available for use, get ready to copy the transmission, and wait for KD8TQI to arrive.
KD8TTE from KD8TQI.
KD8TTE will respond that he is ready to copy traffic.
KD8TTE ready to copy one digital for Bexley.
KD8TQI will announce that he is sending digital traffic in case anyone is monitoring the frequency and wishes to copy the traffic, or wants to avoid having a loud digital transmission fill their room.
KD8TQI sending digital.
KD8TQI will then send the transmission and at the end, will sign to indicate the end of the transmission.
KD8TTE will then respond with voice if there is another transmission required, or a clarification that needs to be made. If the transmission was copied properly, KD8TTE will acknowledge receipt of the message and announce a change in frequency back to the frequency where net control was (146.970 in this case).
Roger. KD8TTE. Returning to 146.970.
KD8TQI will indicate that he is returning back to the frequency as well.
KD8TQI returning to 146.970.
Returning to the Net
Returning to the net from passing digital traffic is exactly the same as if passing the traffic by voice on another frequency. The returning stations will wait for net control to call for stations with or without traffic and announce themselves and what they have done on the other frequency.
KD8TVB: Further stations with or without traffic?
KD8TTE: KD8TTE back, received one digital.
KD8TQI: KD8TQI back, sent one digital.
Net control will then register both stations as back on frequency and eligible for more traffic.