Channel 16 is the international channel for sending distress messages, safety announcements and calling.

This is a bit of a trick question. You do always need some sort of licensing on top of your 'Authority to Operate' certificate, but the specific type of license might not be a Ship's Radio License. For instance, if you travel between boats you might opt for a Ship Portable Radio License. If you were setting up a Sailing Club and needed a shore base station, you might get a Coast Station Radio License.

Whichever license you register for, it is important to double check that it covers the breadth of use you are anticipating, or you could find yourself in hot water with the authorities.

Channel 70 is the only channel that must never be used for voice transmissions. This is because it is reserved for the transmission of digital data from DSC calls. Modern radio sets won't let you make a voice call on Channel 70, although some older ones might... don't try it!

While your dog falling overboard is probably a distressing situation for you, it is not a distress situation for everyone else. Go back to the definition of distress, which states that the grave and imminent danger must apply to a 'vessel, vehicle, aircraft or person'. Therefore, a dog overboard does not warrant a Mayday call.

The squelch controller regulates the sensitivity of the radio receiver. Essentially, you want to have the squelch set as low as possible, so the sensitivity is high. Beware - if you set squelch too low you will hear a loud, jarring static noise.

There are two main reasons you might not need to return the radio:

1. Vessels under 13.7 metres are not required to carry a DSC radio anyway, so if you fit into that category it's perfectly acceptable to not have one.
2. All radios sold since April 2000 have been required to either have a DSC function built in, OR have the capability of being connected to a DSC controller.

You should absolutely never guess your location when giving a distress call. If you are genuinely unsure, then you should be honest about it. The coastguard might ask you to provide details of your point of departure, journey time, and average speed and can have a good estimate at your location themselves - but it will confuse things if you are the one guessing!

The Mayday call is the call used in a distress situation - it takes absolute priority over every other call, except from another Mayday call.

The official definition of distress is:

A vessel, vehicle, aircraft or person must be in grave and imminent danger.

For leisure boaters, that essentially means you are in a distress situation if someone aboard or nearby is dying, or your boat is going to sink.

Modern radio equipment is very reliable, and will rarely fail for no reason. Therefore, if you're using your VHF radio regularly, you should rarely need to do a specific, designated radio check. However, if you know that your radio is a bit dodgy, or you don't use it so regularly, it may be worth doing a check before heading out.

You do not need to carry an EPIRB on a 12-metre vessel, as long as you aren't seeking to use the vessel commercially. That doesn't mean it isn't a good idea, but only means you don't legally have to. The size for 'compulsory fit' (when you have to carry GMDSS equipment) is 13.7 metres.

This is one that catches a lot of people out. It is actually perfectly acceptable to call another vessel or station on Channel 16. As we will generally listen out on Channel 16 through dual watch, it is the logical choice to hail another station. However, any call on Channel 16 (apart from distress and safety calls) must be kept to under 1-minute.

It is far more difficult to get a person back than a training dummy, and survival rates in cold water are low. Additionally, the high-stress of a real MOB situation might lead you to make more errors than in training scenarios. It is not worth trying multiple times to get the person back before calling for help - waste no time and do it immediately. After you have sent your distress call, you may well retrieve the person, in which case you can cancel the distress call or seek further advice.

DSC is the function on a radio to send a digital message to other vessels or another vessel which is also DSC enabled. It may be used for Distress calls, or as a way of hailing another vessel without having to make the initial call via voice.

You should always say OVER at the end of your radio message, when you are expecting a reply from the receiving station(s). You shouldn't use OUT unless you are ending both sides of the transmission, and must never say OVER AND OUT - leave that for TV shows. Some modern radios might send an automatic 'bleep' at the end of the transmission, but this should not be used in place of OVER or OUT, and it does not convey whether you are expecting a reply or not.

It really depends on how deeply you consider the lunch options over the radio. It would be perfectly acceptable to hail another boater on the radio to arrange your rendevous point, but it would not be acceptable to discuss which restaurant you fancy going to, or your previous memories of the spot.