The training theme for December is search procedures. A sensor that can be highly effective in a search is the radio direction finder or RDF. Of course, the boat or person in question needs to broadcast on a VHF marine frequency to make this work. But if they can, you will get a direction to them very easily.
The radio direction finder in Cape Lazo can be used to follow a radio transmission to the source. This may, for example, be a boat, a person, or the datum marker buoy. The source could be a person in the water or on shore if they have a hand-held radio and are transmitting.
The video provides a brief introduction to the radio direction finder or RDF.
Note that there can be some confusion about what is a SHIP channel and what is a COAST channel. Most of our radio channels are simplex (and the others are duplex). Simplex means that all transmitters that have switched to a specific channel will use the same frequency when they are broadcasting. A downside of using a simplex channel is that when one station is broadcasting other stations cannot. Hence the need to say "OVER" when you yield the channel to another station.
So simplex means that any mobile station (usually boats) and any shore station (e.g., Victoria Coast Guard Radio) use one frequency and share it. In this case pressing SHIP, then 1, and then 9 will set the RDF to track all stations on that frequency (156.95 MHz) or channel (19A). The direction given by the RDF will be towards the station that is broadcasting at that instant.
Channels 04A, 15A, 16, and 19A are all simplex channels. Press SHIP, the channel number, and ENTER to start the direction finding process.
Using a duplex channel during a SAR mission would be extremely rare. Duplex means that some transmitters (usually mobile transmitters like those on boats) use one frequency and the other station (usually on shore) uses a different frequency. The main purpose for duplex frequencies is for ship-to-shore "phone calls". On a duplex channel both ends of a conversation can speak at the same time... just like on a telephone. There is no need for a station to end with "OVER" because the other station can go ahead and speak at the same time without causing interference.
For example channel 1 (or 01) is a duplex channel for ship-to-shore telephony or public correspondence. In this case you would find the ship by selecting SHIP, 0, 1, and ENTER and the shore station by selecting COAST, 0, 1, and ENTER.
The use of duplex channels is becoming very rare. The use of cell phones has largely provided a better service than is possible using marine VHF duplex channels. If there is a SAR mission, transmissions will be on Channel 16 or on a simplex channel that is given by Victoria Coast Guard radio.
Once you know the channel a person or persons in distress is using, it should be a simple matter of setting that channel (SHIP, channel number, and ENTER), then following the transmission. Just be sure that the path towards the transmission does not draw you into shallows or dangerous water.
The RDF starts up in direction-finding (DF) mode. It can be switched to receive-only mode by pressing the DF/RCV button (upper right side of the key pad). To return to DF mode press the DF/RCV button again.
Boats equipped with a RDF should probably turn it on at startup and leave it on channel 16. This way as soon as they hear a call for help on 16 they can immediately look at the RDF and see the direction from where the transmission is coming from. Then, perhaps, steering to the source while listening for pertinent information in the transmission. This could save time if the distress vessel in your area of response ability. Also the RDF can be used as a back up VHF monitor if needed.
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