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VHF रादिओस (Very High Frequency)
Without question the Marine VHF Radio is one of the most valuable pieces of safety equipment on board। With channel 16 (for voice) and channel 70 (for digital DSC) being monitored 24 hours a day by the US Coast Guard, the VHF Radio can deliver a call for assistance, allow you to listen to the latest weather report, or simply keep you in touch with other boats on the water।Fixed-
Mount VHF Radios
VHF radios are available in both fixed-mount and hand-held models. All fixed-mount VHFs have a maximum output of 25 watts, the maximum allowed by the FCC. VHF is a line-of-sight system, which means the radio waves won't bend to follow the curvature of the earth. The VHF antenna must "see" the antenna of a distant station. Therefore, antenna height is more important in determining range than radio wattage. The effective useful range of a VHF radio is 20-25 miles.
Hand-Held VHF Radios
VHF handhelds also offer many of the same features found on fixed-mount units. They offer portability in the same way a cordless phone allows more mobility at home. A handheld radio may be just what you need for use in a dinghy, small boat without electrical systems, or as an emergency backup for your boat's radio. Handhelds have a maximum output of six watts. Due to their short antennas, they have a limited range of five miles.
A significant increase in range can be achieved by connecting an external antenna or using a telescoping antenna mounted to the hand-held radio. Battery life varies with the size of the battery pack. Many models have optional battery packs with longer operating times, or greater transmitting power, or both. Some have battery saver circuits that turn off the receiver to save power. The battery life of a handheld can be increased by switching from full transmit power to one watt of transmit power. Handhelds are not DSC capable.
Necessary VHF Channels
The most important channel on a VHF radio is Channel 16, the international distress and calling frequency. Channel 9 is used for hailing, radio checks, plus some other functions. In Florida, for example, 9 is the bridge tender's channel. Channel 6 is for ship-to-ship safety calls after contact is made on another frequency. Channel 13 is for boat-to-boat navigation. Channel 22 is for emergency transmissions once directed by the Coast Guard to switch from another channel. Channels 24-28 and 84-88 are where you'll find a marine operator available to connect you to a land-based line. WX-1-3 are the NOAA weather channels.
DSC Capability
Digital Selective Calling, or DSC, is the equivalent of a "mayday button" on a VHF or SSB. When activated, it automatically broadcasts an encoded distress call that will be picked up by all nearby vessels equipped with DSC. If the radio is interfaced with a Loran or GPS, it will also automatically broadcast the distressed vessel's position. A few high-end radios now include it as a feature, so when it becomes fully operational, your VHF will be able to take advantage of this latest feature. To use DSC, you must obtain a MMSI (Maritime Mobile Service Identity) number. You may do so free of charge at this web address: (click on link or copy and paste into your web browser). http://www.boatus.com/mmsi. Keep in mind that the U.S. Coast Guard is not yet responding to DSC transmissions. Currently, monitoring is scheduled to begin in 2007.
Cellular Telephones
Having a cell phone on board allows you to keep in touch with land-based people and businesses easily. They are very convenient and should be used in tandem with a VHF. Cell phones, although very convenient on land, are less reliable on the water. Most are not water resistant, and their range is relatively short. The maximum range to and from a cell antenna/station varies, but it is basically line-of-sight. Range is further complicated by the fact that the majority of cell antenna/stations are placed with land-based use in mind, so the distance offshore that a vessel can remain in contact is frequently short. Cell phones can also be expensive to operate, although there are many different packages available. Your communication power with a cell phone is limited on the water because the other ship you are trying to contact must also have a cell phone. In some areas, you can place a call to the local Coast Guard station by dialing *CG.
Family Radio Service Radios
Family Radio Service radios are intended for personal, non-commercial use like CB radios. They are very handy because they can be used on land for communication without a license. They are perfect for outdoor trips with friends and family where you need to stay in contact. And they also help with communications while still on the boat. You can talk to each other from bow to stern, from below to above deck, and more! The range is typically 1-2 miles and is line-of-sight like VHFs and cell phones. They have limited battery power and no emergency channel. They operate in the 460mHz UHF band between VHF radios and cell phones and transmit at 0.5 watts. Because these units have become so popular, you may want to pre-arrange what channel you will be using and test it out-very often one or more channels will be overloaded, especially in crowded areas.
CB Radios
Citizen band radio is intended to afford the general public economical access to two-way radio communication. CB is allocated 40 specific frequencies between 26.965 and 27.405 mHz, commonly referred to as channels 1-40. Any channel may be used with either single or double sideband amplitude modulation except Channel 9, which is reserved for emergency communications. CB stations are limited to 4-watt carrier waves output power on DSB AM, and 12-watts PEP on SSB AM. The usual reliable range of CB is five miles. There are several pitfalls to having a CB radio on the water: Making contact may be difficult, since not all boats have CB radios. Channel noise and station traffic are sometimes heavy, and the Coast Guard doesn't monitor the emergency channel.
SSBs
Single sidebands operate in the medium frequency (MF) and/or high-frequency (HF) bands for reliable direct-voice communications over distances exceeding 25 miles (depending on antenna heights). SSBs are commonly available with an output power from 50-150 watts. An SSB's range is affected by the strength of the radiated signal, among other things. The maximum reliable range in the 2-3mHz (MF) band during the day is 50-150 miles. Transmission in HF band can reach thousands of miles.
Unlike VHF radios, SSBs require a large ground plane in order to radiate its signal which except on metal hulls, needs to be installed in the form of a large copper mesh panel (sometimes built onto the fiberglass hull). With SSBs, antenna selection and installation is also more complicated. SSBs generally require a much longer antenna than VHFs, and different antenna tuning for different bands.
Satellite Communications
Iridium is the first example of a worldwide voice communication system which can be accessed using a small hand-held telephone. The 66 iridium satellites have the ability to forward voice phone calls from one another and then relay the conversations to ground stations. Magellan's GSC 100 Personal Satellite Communicator is for those who need worldwide e-mail capabilities. Using 36 ORBCOMM satellites, the constellation allows real-time data communications with low per message costs and low hardware costs.
Our Recommendation
For reliable on-the-water communications, we recommend using either hand-held or fixed-mount VHF radios. When you're stuck in a jam-whether from engine failure or a fierce storm approaching, a VHF radio can be your lifeline to the world. In Coast Guard jurisdictions, VHFs are monitored 24 hours a day, seven days a week. For extra assurance, the USCG towers can locate your boat by tracking your VHF signal. VHFs are handy in an emergency, but they have other uses: telephone calls to shore, obtaining supplies and services such as marina reservations, and boat operations like drawbridge openings and communicating with commercial and other recreational vessels. The Federal Communications Commission (FCC) regulates marine radio traffic and dictates that all other uses are secondary to safety, so chatting is frowned upon by the FCC and forbidden on Channel 16 and 9.
VHF radios are available in both fixed-mount and hand-held models. All fixed-mount VHFs have a maximum output of 25 watts, the maximum allowed by the FCC. VHF is a line-of-sight system, which means the radio waves won't bend to follow the curvature of the earth. The VHF antenna must "see" the antenna of a distant station. Therefore, antenna height is more important in determining range than radio wattage. The effective useful range of a VHF radio is 20-25 miles.
Hand-Held VHF Radios
VHF handhelds also offer many of the same features found on fixed-mount units. They offer portability in the same way a cordless phone allows more mobility at home. A handheld radio may be just what you need for use in a dinghy, small boat without electrical systems, or as an emergency backup for your boat's radio. Handhelds have a maximum output of six watts. Due to their short antennas, they have a limited range of five miles.
A significant increase in range can be achieved by connecting an external antenna or using a telescoping antenna mounted to the hand-held radio. Battery life varies with the size of the battery pack. Many models have optional battery packs with longer operating times, or greater transmitting power, or both. Some have battery saver circuits that turn off the receiver to save power. The battery life of a handheld can be increased by switching from full transmit power to one watt of transmit power. Handhelds are not DSC capable.
Necessary VHF Channels
The most important channel on a VHF radio is Channel 16, the international distress and calling frequency. Channel 9 is used for hailing, radio checks, plus some other functions. In Florida, for example, 9 is the bridge tender's channel. Channel 6 is for ship-to-ship safety calls after contact is made on another frequency. Channel 13 is for boat-to-boat navigation. Channel 22 is for emergency transmissions once directed by the Coast Guard to switch from another channel. Channels 24-28 and 84-88 are where you'll find a marine operator available to connect you to a land-based line. WX-1-3 are the NOAA weather channels.
DSC Capability
Digital Selective Calling, or DSC, is the equivalent of a "mayday button" on a VHF or SSB. When activated, it automatically broadcasts an encoded distress call that will be picked up by all nearby vessels equipped with DSC. If the radio is interfaced with a Loran or GPS, it will also automatically broadcast the distressed vessel's position. A few high-end radios now include it as a feature, so when it becomes fully operational, your VHF will be able to take advantage of this latest feature. To use DSC, you must obtain a MMSI (Maritime Mobile Service Identity) number. You may do so free of charge at this web address: (click on link or copy and paste into your web browser). http://www.boatus.com/mmsi. Keep in mind that the U.S. Coast Guard is not yet responding to DSC transmissions. Currently, monitoring is scheduled to begin in 2007.
Cellular Telephones
Having a cell phone on board allows you to keep in touch with land-based people and businesses easily. They are very convenient and should be used in tandem with a VHF. Cell phones, although very convenient on land, are less reliable on the water. Most are not water resistant, and their range is relatively short. The maximum range to and from a cell antenna/station varies, but it is basically line-of-sight. Range is further complicated by the fact that the majority of cell antenna/stations are placed with land-based use in mind, so the distance offshore that a vessel can remain in contact is frequently short. Cell phones can also be expensive to operate, although there are many different packages available. Your communication power with a cell phone is limited on the water because the other ship you are trying to contact must also have a cell phone. In some areas, you can place a call to the local Coast Guard station by dialing *CG.
Family Radio Service Radios
Family Radio Service radios are intended for personal, non-commercial use like CB radios. They are very handy because they can be used on land for communication without a license. They are perfect for outdoor trips with friends and family where you need to stay in contact. And they also help with communications while still on the boat. You can talk to each other from bow to stern, from below to above deck, and more! The range is typically 1-2 miles and is line-of-sight like VHFs and cell phones. They have limited battery power and no emergency channel. They operate in the 460mHz UHF band between VHF radios and cell phones and transmit at 0.5 watts. Because these units have become so popular, you may want to pre-arrange what channel you will be using and test it out-very often one or more channels will be overloaded, especially in crowded areas.
CB Radios
Citizen band radio is intended to afford the general public economical access to two-way radio communication. CB is allocated 40 specific frequencies between 26.965 and 27.405 mHz, commonly referred to as channels 1-40. Any channel may be used with either single or double sideband amplitude modulation except Channel 9, which is reserved for emergency communications. CB stations are limited to 4-watt carrier waves output power on DSB AM, and 12-watts PEP on SSB AM. The usual reliable range of CB is five miles. There are several pitfalls to having a CB radio on the water: Making contact may be difficult, since not all boats have CB radios. Channel noise and station traffic are sometimes heavy, and the Coast Guard doesn't monitor the emergency channel.
SSBs
Single sidebands operate in the medium frequency (MF) and/or high-frequency (HF) bands for reliable direct-voice communications over distances exceeding 25 miles (depending on antenna heights). SSBs are commonly available with an output power from 50-150 watts. An SSB's range is affected by the strength of the radiated signal, among other things. The maximum reliable range in the 2-3mHz (MF) band during the day is 50-150 miles. Transmission in HF band can reach thousands of miles.
Unlike VHF radios, SSBs require a large ground plane in order to radiate its signal which except on metal hulls, needs to be installed in the form of a large copper mesh panel (sometimes built onto the fiberglass hull). With SSBs, antenna selection and installation is also more complicated. SSBs generally require a much longer antenna than VHFs, and different antenna tuning for different bands.
Satellite Communications
Iridium is the first example of a worldwide voice communication system which can be accessed using a small hand-held telephone. The 66 iridium satellites have the ability to forward voice phone calls from one another and then relay the conversations to ground stations. Magellan's GSC 100 Personal Satellite Communicator is for those who need worldwide e-mail capabilities. Using 36 ORBCOMM satellites, the constellation allows real-time data communications with low per message costs and low hardware costs.
Our Recommendation
For reliable on-the-water communications, we recommend using either hand-held or fixed-mount VHF radios. When you're stuck in a jam-whether from engine failure or a fierce storm approaching, a VHF radio can be your lifeline to the world. In Coast Guard jurisdictions, VHFs are monitored 24 hours a day, seven days a week. For extra assurance, the USCG towers can locate your boat by tracking your VHF signal. VHFs are handy in an emergency, but they have other uses: telephone calls to shore, obtaining supplies and services such as marina reservations, and boat operations like drawbridge openings and communicating with commercial and other recreational vessels. The Federal Communications Commission (FCC) regulates marine radio traffic and dictates that all other uses are secondary to safety, so chatting is frowned upon by the FCC and forbidden on Channel 16 and 9.