Article by Pat Schrawder
GETTING THE FULL USE OF YOUR VHF & DSC
By now, most boaters have a VHF that is new enough to have a DSC/Distress button on the front. That feature is required for all VHF’s manufactured today and has been for a while. If you are not sure, look at your VHF front panel. It should have a red button marked DSC or Distress.
The primary importance of DSC is for emergency distress alerts. In an emergency on your boat, you simply have to flip up the cover, press the button, and a distress signal will be sent that includes your location; provided you have connected your GPS unit to your VHF.
What I’d like to talk about today; however, is the other uses of the Digital Selective Calling feature. I will address these functions in general since different brands of VHF’s have different operating procedures. You will need to consult your manual to find out exactly what buttons to push, etc., to use these features.
Digital Selective Calling is a feature that allows you to program multiple ID numbers and names for persons with whom you wish to communicate from your boat. Both you and your “friend” must have obtained an MMSI number (9 digit ID that you can get for free from the following link): http://www.boatus.com/mmsi
You must program those various 9 digit ID numbers into your VHF and give them each a name. You can also select two or more of them to put into a group, and you can have more than one group. It works much the same as your email address file. This enables you to call and converse with just certain people or groups. You pre-select a particular channel to use (hopefully one that is not heavily used by other boats). When you make a “selective” call, the request goes out to your intended receiver. Once a connection has been made, both radios will automatically switch to the pre-selected channel for you to continue your conversation.
Another very useful feature of selective calling is the “position request and reply” call. With this function, you can select an individual or group and send a DSC selective call to them requesting to know their location. The person to whom you sent your call request to will make a corresponding “position reply” call back to you, showing you their location in latitude and longitude as determined by their GPS. If it is connected to your VHF, the location can transmit itself automatically. If you have not, there should be provision for you to input your location manually.
Distress calls and Digital Selective Calling calls are both automatically transmitted initially on Channel 70. For that reason, it’s a good idea to monitor that channel, particularly if you are expecting a call. Some VHF radios are capable of monitoring channel 70 at the same time you are actively using another channel. This is a very useful feature.
Depending on your particular VHF, you may have noticed something that looks like an envelope that suddenly appears on your radio’s display screen. That is normally an indication that an emergency Distress call has been transmitted in your vicinity. You can switch from your active channel to channel 70, and see if it displays a request for acknowledgement of receipt of the distress call.
As you can see, the Distress feature and the Digital Selective Calling feature are two very different types of calls. Before using either of them, read your manual carefully and make sure you understand the process so that you do not ever accidently send a distress call. Also keep in mind that, although you can selectively call certain other radios (boats), once you make contact, your conversation is not private.
Pat and her husband, Larry are owners of L&L Marine Electronics on Golf Course Road in West Ocean City, MD.
