Safety update

February 1997 Marine VHF: Accidental transmissions

This safety update is for operators of marine VHF. It is issued to raise awareness of the potential serious risk to safety from accidental transmissions. It provides safe practice tips for how best to reduce the risks involved and to alert people to the risk to safety associated with accidental transmissions.


Marine VHF radiotelephone operators are urged to take extra care to ensure that the distress channel, Channel 16, is not blocked by accidental transmissions.

Recently a number of accidental transmissions, lasting several hours at a time, have made Channel 16 unusable to those requiring assistance and to those listening for calls for assistance. This could cause very serious consequences for people in dire situations.

Safe practice tips

Operators are asked to ensure that they avoid blocking the channel, which is usually caused by two circumstances:

  • stowing the microphone in a way that causes its "press to talk" switch to be jammed on and the VHF to transmit. This could happen when the microphone is placed between two items on a shelf rather than hung on the microphone clip.
  • a fault developing within the VHF which causes it to transmit.

Operators of marine VHF should ensure that they:

  • stow the VHF microphone on the microphone clip when it is not in use
  • check the VHF periodically to ensure a fault has not developed and that the apparatus is not accidentally transmitting.

Simple VHF Test

If you suspect that a VHF may have developed an internal fault and may be constantly transmitting, a simple test is to ensure the volume is set at the normal level, then wind the "squelch" adjustment back until a static sound is heard.

If the squelch adjustment is wound right back to the minimum position and no static sound is heard the VHF may be faulty and in constant transmission.

In this case the set should be turned off to avoid interference to other maritime users.

Original source content - Boat Notice 011997, February: Marine VHF: accidental transmissions.

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