Hi everyone,
For some years we've been using DSC routine calling on VHF. It is useful for contacting ships at sea (to arrange separation) and also for meeting another yacht directly on a working channel without having everyone in range follow you there from channel 16.
In 2012 we started looking into using DSC on our
HF/SSB. This blog describes how we configure and use DSC on our Icom.
!!WARNING!! This is just how we use our radio. Your needs may differ from ours. !!WARNING!!
What is HF DSC?
DSC stands for Digital Selective Calling. It uses digital transmissions so has better propagation characteristics than voice. DSC is best known for its use in sending distress calls, but it supports a broad range of uses.
DSC calls have various characteristics:
- Purpose:
- to negotiate a traffic frequency for voice communication
- to communicate GPS position (requires NMEA0183 GGA sentence input to radio)
- both of the above (eg in a safety/mayday situation)
- Addressing:
- Individual
- Group
- Area (geographical)
- All Ships (broadcast)
- Categories:
- Distress (Mayday)
- Urgency (PanPan)
- Safety (Securite)
- Routine
Unfortunately routine calling is made difficult by Icom's default configuration. By default they are configured only with emergency channels. Using emergency HF DSC channels for routine traffic is not permitted. Happily reconfiguring the radio isn't difficult (tedious perhaps but not difficult).
Note that Icom M801E and M802 units have two antenna connections. One is to the main transceiver and the other is to a second receiver. The latter continuously scans the six main emergency DSC frequencies - regardless of what the main transceiver is doing. The second antenna can be a piece of insulated wire, 4-8 metres long, run around inside the boat (unless the hull is metal).
History
Way back in 2007 US-based KA7WJA of sv Annie Laurie posted a suggested reprogramming of the M802 to support routine calling. See that posting
here. More recently Commander T L Sparks published a book "Icom IC-M802 Made Simple for Cruisers". The book describes the same method in detail. The book only appears to be available via eBay.
Configuration Overview
All DSC-related configuration can be done manually on either M801E or M802. It is possible to purchase Icom's CS-M802 configuration software for the M802. I'll describe manual configuration here but first here is a screenshot from the software showing the DSC Rx/Tx Frequencies table...
The table lists three types of frequencies...
- Call = DSC data frequency
- Scan = Up to six DSC call frequencies to be scanned for incoming calls in DSC Watch
- Traffic = voice frequencies the radio can switch to after the DSC call completes
The scan frequencies are all routine DSC call channels which suits boats with the second antenna connected. If you don't have the second antenna you may wish to configure three emergency channels and three routine channels - for example pairs in the 4, 8 and 12 MHz bands.
MMSI Check
DSC won't work at all without your MMSI configured. Here is the procedure to check it...
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| 1. Click DSC key to enter DSC Watch the click MODE button |
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| 2. Scroll (using CH dial) to Setup and click ENT button |
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| 3. Scroll to MMSI Check and click ENT button |
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| 4. Check your MMSI is correct then click ENT to exit MMSI Check or/then MODE to exit to DSC Watch |
The above procedure also serves as an introduction to navigating the DSC menus. The text at the bottom of the screen should show you your options with reverse-video showing the button to use and the normal video showing the action which results. However this isn't always intuitive. For example at step 3 clicking CH should select but actually moves you back one level in the menus.
If you don't have an MMSI it's "game over" until you do. If you but it is not configured then follow the instructions in the manual to configure it - very carefully! With that done, read on!
Scan Frequency Configuration
Next we will replace the existing scan frequencies with frequencies intended for routine calling. We can do this since our second antenna keeps on listening to the emergency frequencies regardless. The scan frequencies should be configured as illustrated in the table in the Configuration Overview section above. Note that all frequencies are simplex so Tx=Rx. Here's the procedure, starting from the DSC Setup menu...
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| 1. Scroll to Scan Frequency and click ENT button |
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2a. Scroll to each tx/rx frequency in turn and click ENT button
2b. Push and hold CE button until beep to delete the frequency
2c. goto 2a and repeat until all 6 frequencies deleted
(Note - the image above shows a configuration for a radio with only one antenna) |
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3a. Scroll to <add> and click ENT button
3b. Enter the Comment, TX and RX fields, with a leading zero in frequency fields if necessary
3c. Click the ENT button when fields correct
3d. goto 3a and repeat until all 6 frequencies added |
At the end of this procedure you should have six new scan frequencies. Your radio can now receive and respond to incoming DSC calls. To confirm correct configuration return to the DSC Watch screen and you should see the newly configured frequencies being scanned.
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| Expect to see the screen cycling through the six routine frequencies configured |
Call Frequency Configuration
Next we will replace the existing call frequencies with frequencies intended for routine calling. The call frequencies include the six scan frequencies plus others we don't scan. This is to ensure we have them somewhere in case we wish to change the scan. The call frequencies should be configured as illustrated in the table in the Configuration Overview section above. Note that all frequencies are simplex so Tx=Rx. Here's the procedure, starting from the DSC Setup menu...
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| 1. Scroll to Call Frequency and click ENT button. |
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2a. Scroll to each tx/rx frequency in turn and click ENT button
2b. Push and hold CE button until beep to delete the frequency
2c. goto 2a and repeat until all frequencies deleted |
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3a. Scroll to <add> and click ENT button
3b. Enter the Comment, TX and RX fields, with a leading zero in frequency fields if necessary
3c. Click the ENT button when fields correct
3d. goto 3a and repeat until all frequencies added |
Traffic Frequency Configuration
Next you will replace the existing traffic frequencies with the voice frequencies you frequently use for talking with other stations. These can be any marine band ship to ship channel. Our list copies the User Channels we have configured in the radio. Your traffic frequencies can be configured as illustrated in the table in the Configuration Overview section above, or with whatever traffic channels you prefer to use. It is logical to include at least one traffic frequency in each band having a call frequency configured. Here's the procedure, starting from the DSC Setup menu...
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| 1. Scroll to Traffic Frequency and click ENT button. |
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2a. Scroll to each tx/rx frequency in turn and click ENT button
2b. Push and hold CE button until beep to delete the frequency
2c. goto 2a and repeat until all unwanted frequencies deleted |
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3a. Scroll to <add> and click ENT button
3b. Enter the Comment, TX and RX fields, with a leading zero in frequency fields if necessary
3c. Click the ENT button when fields correct
3d. goto 3a and repeat until all frequencies added |
Your radio is now configured to send as well as receive DSC calls!
Configuring Address IDs
It is convenient to configure a set of stations in the radio's "Address Book". This causes the radio to show their name instead of their MMSI which is much easier to work with. We configure boats we are sailing with and also RCCs (Rescue Coordination Centres) in our cruising area. Here is the procedure to add a single entry from the DSC Setup menu...
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| 1. Scroll to Address ID and click ENT button. |
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| 2. Scroll to <add> and click ENT button |
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3. Enter Name, ID, TX and RX fields then click ENT
Note that the TX and RX fields should match one of your calling frequencies |
Configuring Group IDs
Group IDs allow the transmission of DSC calls which do not require acknowledgement. All stations in the group ring an alarm and the operator can accept the call to have the radio change to the nominated traffic frequency - a nice way to start a sked!
Group IDs (ie MMSIs) are normally a simple juggle of the ship's MMSI. Shift all the numbers right by one digit and add a zero at the front. That's your vessel's Group ID. So Zen Again's MMSI of 503433900 translates into our Group ID of 050343390. Join us now!
Making a DSC Call
There are a number of menus to step through to make a DSC call. Fear not - they are mostly self-explanatory! Here's the procedure to make an individual, routine call to Vulcan Spirit from Zen Again...
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| 1. Scroll to Individual and click ENT button. |
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| 2. Scroll to Routine and click ENT button |
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| 3. Scroll to Vulcan Spirit and click ENT button |
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| 4. Scroll to the traffic (ie voice) frequency you wish to talk to them on and click ENT button |
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| 5. Scroll to the call frequency you wish to call them on and click ENT button |
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6. The call is now setup and read to go.
6a. Push and hold CALL until the radio beeps and starts transmitting; or
6b. Click ENT button to add this call into one of 10 Transmit Memories |
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| 7. Presuming you CALLed, you should see a screen like this for several seconds |
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8a. Then the radio waits for an acknowledgement from the recipient.
Note - the recipients radio must be on, in DSC Watch and they need to check the radio screen regularly!
8b. When acknowledgement received click FREQ to change to the traffic frequency
8c. Use the radio as normal to communicate with the other vessel |
Conclusion
I hope the information presented here is useful. This blog will be expanded over time as I manage to capture screenshots showing acknowledgements etc. Comments welcome!
