Maritime Radio Communications

VHF (Very High Frequency) Radio Required in the form of a ‘bridge to bridge’ marine radio on commercial vessels. Some smaller (non-commercial) vessels are exempt from the requirement. However most have them anyway (in US waters at least). VHF is defined as the frequency range from MHz, however marine VHF radios only use freqs from 156MHz to 157.5MHz.

Common VHF Channels 9 Hailing, Commercial and Non-commercial 12 Port Operations, Annapolis Harbor Control 13 Inter-ship Navigation Safety, Bridge to Bridge* 16 International Safety, Distress, Calling* 22A US Coast Guard and Maritime Safety Broadcasts 82A US Government only, Navy Sailing working channel* Navy 44 VHF lists nature of VHF channel on screen readout Eldridge provides channels for calling certain Harbormasters, bridges, etc. Full list at * denotes channels that required to be guarded

VHF Propagation and Limitations VHF signals generally follow a line of sight path, meaning they will not reach over the apparent horizon of your antenna. The signal strength loss is proportional to the distance the signal travels. Signal strength is reduced by roughly 75% every time the distance traveled is doubled. This means you should use the highest transmit power setting for long distance calling. Foul weather can increase signal attenuation and distortion, but this is more of a problem at lower frequencies. A condition known as Tropospheric Ducting can occur from time to time due to stark gradient changes in moisture, temperature and pressure profiles between roughly ,000 ft. This effect can trap and reflect VHF signals in a manner similar to the ionospheric reflection of sky waves, greatly increasing the range the signal travels.

HF (High Frequency) Radio HF ( or SSB - single side band) marine radios are used for long range communications. Due to their unpredictable nature, most vessels have substituted satellite communications for long range application and keep HF radios for emergency back up. HF is defined as the frequency range from 3-30 MHz. In our application we use 4 specific frequencies as outlined in the Summer OPORD. Navy Sailing HF freqs: – KHz – KHz – KHz – KHz

HF Propagation and Limitations Ground waves: This propagation path follows the curvature of the Earth and therefore it is possible to conduct direct, over the horizon communication. HF bands have a more limited range than VLF and LF bands in this mode however. Sky waves: This mode is of the greatest importance to HF comms and is also known as skip. It relies upon bouncing the signal off the ionized upper layers of the atmosphere, giving the signal long but indirect range. This also produces blackout areas. Because this method relies on the level of ionization of the upper atmosphere, ranges, most useful freqs and interference will vary depending on the time of day, weather, yearly season and the 11 year sun spot cycle.

Sky Wave diagram

SOP and Pro-Words Use the format ‘station being called’ this is ‘station calling’ ‘message’, over (out). – Do not use double call ups Out- this is the end of my transmission and no response is required or expected Over- this is the end of my transmission and your response is required Roger- your last transmission was satisfactorily understood Wait (Out)- I must pause for a few seconds (more than a few seconds Break- I indicate a separation of the following text from previous parts of the message

Pro-Words cont. Say again- repeat your last transmission or portion indicated I say again- I am repeating the message or portion indicated All after (before)- the portion of the message I reference is everything after (before) the indicated portion Disregard this transmission- this transmission was in error, disregard Relay to- transmit this message to all addresses immediately following the proword I spell- I am spelling the word phonetically Securite- information is being provided regarding safety of navigation (buoy out of position, approaching a blind turn) Pan-Pan- info is being provided regarding an urgent but not necessarily life threatening situation (fire or flooding onboard) Mayday- info regarding being in grave or imminent danger, usually of the life threatening variety (my boat’s sinking)

Radio Etiquette Be clear and concise Do not hold conversations on hailing channels – Usually an issue on CH 16 Do not say “Break” three times in a row, on certain circuits it’s the equivalent of a Mayday call State what channel you are transmitting on Before keying to transmit, listen to ensure the channel is not in use and THINK about what you want to say BEFORE you say it

Radio Etiquette Cont. YOU MAY NOT TRANSMIT -- False distress or emergency messages. Messages containing obscene, indecent, or profane words or meaning. Yes, it’s actually illegal. General calls, signals, or messages, except in an emergency or if you are testing your radio (these are messages not addressed to a particular station)

Examples and Questions Hailing another vessel Arranging passage Securite call QUESTIONS?