It seemed obsolete, but the old Vhf had a surge of pride. Everything you never dared to ask the on-board “radio”. We cornered him and got him to tell us the whole truth of his success.
Why is the Vhf the most popular tool for communications at sea?
The secret to the reliability of the Vhf radio in the boat depends on the type of waves it uses for message transmission. These are frequencies that allow clearer long-distance communication because they are less subject to atmospheric interference or interference caused by other waves in the ether.
What kind of waves are used and why?
Vhf radio uses metric, very high-frequency waves called VHF (Very High Frequency) between 156 and 174 Mhz, whose wavelength is approximately 2 meters. The size of its antenna, about half the wavelength itself, makes Vhf communications ideally suited for all vessels, from large passenger ships to smaller fishing boats or pleasure yachts. But other types of waves are also adopted at sea, such as hettometric, medium-frequency (MF) waves, used for medium-distance communications from units that are 100/200 miles from the coast, and decametric, high-frequency (HF) waves used on the high seas, for example, in oceanic navigation.
What are the basic characteristics of a VHF radio?
All models allow background noise to be filtered out via squelch, which allows the sensitivity of the receiver to be set. On the package of each radio you will find the power rating indicated. The maximum emission value granted to recreational boating equipment is 25 watts, with the possibility of reducing it to only 1 watt to limit power consumption and to communicate at close range.
At what distance is it possible to hear each other, with a VHF radio?
With the same emission power, the distance to which Vhf communications can reach depends on the height at which the antennas involved are placed. For example, a range of 60 miles can only be determined between a vessel and a coastal station, while between two vessels the range is reduced to only 15 miles or even less if they are small vessels. Beyond the emitting power of radio equipment, in fact, the discriminating factor is mainly the earth’s curvature. The range, which in this case is called the optical range, will only be able to cross the horizon line if the two antennas still continue to see each other, and result. Vhf radio waves are less susceptible to interference, thus the safest to use at sea. But pay attention to the location of the antenna above the geographical location according to their respective heights. In these cases, sailboats are certainly advantaged by the possibility of installing the antenna at the masthead, considering, however, that it is effective only when operating vertically; when tilted it can lose up to 40 percent of its performance.
Can a portable device also be used on board?
For a few years now, the portable Vhf can finally replace the fixed on-board station in Italy as well. The portable radio on board is increasingly of extreme use: it allows one to make or receive calls while remaining at the helm, keep listening on 16 without having to go below deck, and carry it with one for various eventualities, including the unfortunate transfer to the life raft while leaving the vessel.
What are the main differences between a portable and a stationary model?
Portable radios are now increasingly inexpensive and morphologically similar to cell phones. But beware that although they can support most of the functions of fixed models in fact they are subject to three fundamental drawbacks: – a reduced output power of only 5 watts (instead of 25), in order to contain the consumption of rechargeable batteries; a limited range due to the short length of the antenna; and an operating range that depends on the kind of batteries used and the opportunity for recharging. For proper use of a portable and especially legalized model, it is necessary that each device be registered on the Operating License of the fixed apparatus on board, if any, or provide for its own document, titled to the vessel on which it is used or in the name of the user himself, who in turn must have the appropriate limited radiotelephone certificate.
Why are channels used for boating and not frequencies?
To simplify the use of the equipment, through international agreements, it was agreed to divide the frequencies of use into channels. Each therefore corresponds to a specific frequency, for example, channel 16 corresponds to 156.8 mHz.
What should be checked to choose a good VHF?
The basic characteristics of a radio concern receiver sensitivity, that is, the ability to acquire even weak signals, transmit power to be heard more clearly, and the
selective capacity, which allows it to stay on the frequency of the chosen channel without “overshooting.” Added to these are the operating range of the dirty signal filter, called the squelch threshold, power consumption (important especially in laptops) in both Hi and Low, standby (lowest consumption) and transmission (highest consumption). Then the physical details of the device count: size, weight, and robustness, to which are added the readability of the screen, ease of use, ergonomics, and the amount of additional functions. The mix of these elements makes it possible to judge the last parameter, which is the acquisition cost.
Do you need any special requirements to be able to speak on the VHF?
Use of the Vhf is under the full responsibility of the master of the boat.No one on board may appropriate it without his or her approval. The document mandatorily required to operate Vhf radio is the RTF certificate (Restricted Radiotelephone Operator’s Certificate for Ships), which is issued, without examination, by the Regional Inspectorates of the Ministry of Communications, and is valid on pleasure craft and ships up to 150 gross tons and with radio stations of power not exceeding 60 watts.
What documents are needed to install VHF on the boat?
By equipping yourself with an apparatus of a type that complies with European EC directives (conformity is declared directly by the manufacturer), it is necessary to apply for the appropriate Operating License by contacting the harbormaster’s office where the unit has been registered, so as to also obtain the international call sign number, which is essential for jointly identifying the radio station and the vessel using it. Instead, owners of vessels or portable apparatuses, should address the request directly to the Territorial Inspectorates of the Ministry of Economic Development, Communications Department, and will also obtain a personal code identifying the apparatus and its owner.
DSC stands for Digital Selective Calling: basically, it is a radio function that allows distress calls to be made on a frequency reserved for digital calls only, channel 70, where voice communications are barred and consequently traffic and interference are reduced, instead of on channel 16. This is an extremely useful feature in emergencies, which not only keeps communication time down but also increases its effectiveness and message coverage. In case a distress call is needed, for example, the DSC unit can automatically transmit a large amount of information within seconds to all units equipped with the same system in the navigation area, without having to wait for voice responses and without wasting time repeating calls and details. The DSC distress message provides:
– the vessel’s MMSI, a specific identifier that makes its specific characteristics immediately recognizable;
– The location of the ship, provided by the interfaced GPS, if any, or entered manually;
– UTC indicating the time when the last position was updated;
– The nature of the danger or harm incurred by the applicant.
In addition to distress calls (Medé), emergency (Pan Pan), security (Securité) or ordinary (Routine) calls can also be transmitted (or received), which can then continue in voice form. The voice and digital systems coexist and offer two joint and alternative opportunities for making communications. The DSC system belongs to the instruments adopted by the GMDSS, is associated with communication equipment in Vhf, MF or HF, and is compulsorily present on every unit carrying out navigation for professional purposes.
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