Why is an antenna coupler/tuner required for MF-HF transmissions?

Proper watchkeeping includes the following:

Which statement regarding an MF/HF DSC Distress alert is true:

What is the best method for a GMDSS Radio Operator to determine which SITOR (NBD...

What is usually the first step for a GMDSS Radio Operator to take when initiatin...

Which of the following is a correctly formatted Inmarsat-C address book entry fo...

Which of the following would indicate an Inmarsat-C terminal?

What signal is detected as originating from an AIS SART and how is the signal di...

To request medical assistance from Inmarsat via voice what would be the correct...

How many digits are in the MID (Maritime Identification Digits)?

What will cause an individual battery cell to reverse polarity.