Tuesday, April 27, 2010
Installing a Shakespeare Marine Antenna for your VHF Marine Radio
As is the case with most antenna, the higher your Shakespeare marine antenna is the further you will be able to communicate. If the boat is operating on a lake then distances are not so much of a problem. But if the boat is operating at sea then distance becomes a problem and choosing the correct Shakespeare marine antenna becomes more important.
The radio waves from a marine VHF radio travel in straight lines so your marine antenna has to be able to see the other antenna in order to communicate with it. As the distance increases between marine antennna, they fall below the horizon and curvature of the earth decreases line of sight.
The first step in choosing a Shakespeare marine antenna is to decide on how much range is needed. Getting the maximum range possible based on where the boat operates and the limitations posed, is always optimum.
In order to get approximately 5 miles range, a 3-foot marine antenna would usually suffice. If another boat in your vicinity also had a 3-foot marine antenna connected to their marine radio, you are essentially getting 10 mile range (5 miles for your boat and 5 miles on the other boat).
Gain, which is measured in dB, helps focus the marine antenna energy which makes the antenna more efficient and powerful. When choosing how much gain is needed on your antenna it helps to adhere to these basics.
If you have a sailboat, then you have the advantage of a long mast onto which the marine antenna can be located. A sailboat should normally use a 3 dB gain antenna. Boats that normally operate in calm waters should use a 9dB Shakespeare marine antenna and ski boats and power boats should use a 3dB or 6dB marine antenna.
The mounting of the Shakespeare marine antenna is important. Rail mountings include ratchets which allow lowering of the marine antenna. This is helpful when boats are trailered and covered. It also helps when boats are operating in tree lines - like fishing boats. The ratchet mount also helps compensate for surfaces that are not completely horizontal or vertical.
When mounting your Shakespeare marine antenna for your marine radio try an always mount the antenna as high as possible. Mount it away from large metal objects and keep it away from other antennas on the boat. Mount it 3 feet or more from the marine radio.
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Wednesday, November 18, 2009
Marine Radio - VHF Radio - Marine Antenna
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Monday, July 20, 2009
Types of equipment
Sets can be fixed or portable. A fixed set generally has the advantages of a more reliable power source, higher transmit power, a larger and more effective aerial and a bigger display and buttons. A portable set (often essentially a waterproof, VHF walkie-talkie in design) can be carried to a lifeboat in an emergency, has its own power source and is more easily water-proofed.
Marine radios can be "voice-only" or can include "Digital Selective Calling" (DSC).
Voice-only equipment is the traditional type, which relies totally on the human voice for calling and communicating.
Digital Selective Calling equipment, a part of the Global Maritime Distress Safety System (GMDSS), provides all the functionality of voice-only equipment and, additionally, allows several other features:
- a transmitter can automatically call a receiver equipped with Digital Selective Calling, using a telephone-type number known as a Maritime Mobile Service Identity or MMSI. Such calls take place on Channel 70.
- a distress button, which automatically sends a digital distress signal identifying the calling vessel and the nature of the emergency
- a connection to a GPS receiver allowing the digital distress message to contain the distressed vessel’s position
The MMSI is a nine digit number identifying a VHF set or group of sets. The left hand digits of MMSI indicate the country and type of station. For example, here are MMSI prefixes of four station types:
- Ship : 232, 233, 234 or 235 are the United Kingdom – e.g. a UK ship : 232003556
- Coast : 00 – e.g. Solent Coastguard : 002320011
- Group of stations : 0 – e.g. 023207823
- Portable DSC equipment : for UK 2359 - e.g. 235900498
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Operating procedure
The accepted conventions for use of marine radio are collectively termed "proper operating procedure." These conventions include:
- Listening for 2 minutes before transmitting
- Using Channel 16 only to establish communication (if necessary) and then switch to a different channel
- using a set of international "calling" procedures such as the "Mayday" distress call, the "Pan-pan" urgency call and "Securité" navigational hazard call.
- using "pro-words" based on the English language such as Acknowledge, All after, All before, All stations, Confirm, Correct, Correction, In figures, In letters, Over, Out, Radio check, Read back, Received, Repeat, Say again, Spell, Standby, Station calling, This is, Wait, Word after, Word before, Wrong
- using the NATO phonetic alphabet: Alpha, Bravo, Charlie, Delta, Echo, Foxtrot, Golf, Hotel, India, Juliet, Kilo, Lima, Mike, November, Oscar, Papa, Quebec, Romeo, Sierra, Tango, Uniform, Victor, Whiskey, X-ray, Yankee, Zulu
- using a phonetic numbering system based on the English language: Wun, Too, Tree, Fow-er, Fife, Six, Sev-en, Ait, Nin-er, Zero, Decimal
Slightly adjusted regulations can apply for inland shipping, such as the Basle rules in Western Europe.
Marine VHF radio is sometimes illegally operated inland. Since enforcement is often the job of the local coast guard, enforcement away from the water is sometimes difficult.
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Marine VHF radio
Marine VHF radio is installed on all large ships and most motorized small craft. It is used for a wide variety of purposes, including summoning rescue services and communicating with harbours, locks, bridges and marinas, and operates in the VHF frequency range, between 156 to 174 MHz. Although it is widely used for collision avoidance, its use for this purpose is contentious and is strongly discouraged by some countries, including the UK.
A marine VHF set is a combined transmitter and receiver and only operates on standard, international frequencies known as channels. Channel 16 (156.8 MHz) is the international calling and distress channel. Channel 9 can also be used in some places as a secondary call and distress channel. Transmission power ranges between 1 and 25 watts, giving a maximum range of up to about 60 nautical miles (111 km) between aerials mounted on tall ships and hills, and 5 nautical miles (9 km) between aerials mounted on small boats at sea-level. Frequency modulation is used.
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