How do you call the Coast Guard in an emergency?

How do you call the Coast Guard in an emergency?

People in an emergency and need of Coast Guard assistance should use: VHF-FM Channel 16 (156.8 MHz), dial 911. For general inquiries call your nearest Coast Guard unit.

What radio frequency Do ships use?

VHF Radiotelephone (156-162 MHz) – Used for voice communications with other ships and coast stations over short distances. Digital Selective Calling (DSC) – Used with VHF, MF, and HF radio systems to establish communications with (call) ships or coast stations or to receive calls from other ships or coast stations.

Which VHF channels can I use on land?

channels: 462.5625, 462.5875, 462.6125, 462,6375, 462.6625, 462.6875 and 462.7125.

Why is height of a VHF radio antenna important?

When considering marine VHF radio communications, more important than all other factors is the height of your antenna. The higher you can place your VHF antenna the further you will be able to communicate. Any angle beyond vertical will lessen the performance of your radio signal.

How far will a 5 watt VHF radio transmit?

12 miles

How far does a VHF radio reach?

about 60 miles

How long should a VHF antenna be?

A 3- to 4-foot antenna that’s 3 dB is generally recommended for boats under 24 feet. Larger vessels can opt for 12- to 18-foot, 7 to 8 dB antennas. “As a general rule, antenna height should be less than half the length of the boat,” Catoe says.

Does a VHF antenna need to be grounded?

VHF antennas that come with an integrated ground plane do not need to be grounded. VHF antennas that do not have an integrated ground plane must be grounded, and their instruction manual will tell you how. Either way, you need to consult the installation instructions for the antenna that you buy.

Does a VHF need an antenna?

VHF needs an antenna. You can connect an antenna directly to the unit or very close to it but the antenna is a must. Transmission and receipt is much better if the antenna is at higher levels but you can receive and transmit with an antenna inside the boat, but the antenna should be connected to the radio.

Does a VHF antenna need to be vertical?

To answer your question directly, no, you cannot have one vertical and one horizontal antenna.

How do I know if my VHF antenna is working?

Remove the connector on the antenna cable from the back of your radio. Insert the tip of a small screwdriver or paper clip into the center contact of the radio’s antenna jack while monitoring your local weather channel. If you can hear the weather broadcast, your radio most likely has good reception.

Which of the following is the best placement of a VHF aerial?

The received wisdom seems to be that the best VHF antenna is a 1/2 wave, center-fed dipole placed at the top of the mast. These don’t require a ground plane and have modest gain so that they are less affected by heeling than a higher-gain antenna might be.

What is inside a VHF antenna?

There inner electrical element (the part that radiates and receives signals) of VHF antennas is generally made of one of three types of materials: coaxial cable, copper or brass. While all provide acceptable performance, better antennas use brass or copper for optimum performance and durability.

Do VHF antennas go bad?

The antennas do not actually ever “go bad” however just like everything they are susceptible to water damage. If yours is sealed and has no signs of corrosion it will be fine. All that is inside of them is a wire of the proper wave length, keep it dry and it will last forever.

Do I need a special antenna for AIS?

For this scenario a VHF antenna is needed. An AIS antenna will be tuned to AIS frequency of 162 MHz. VHF antennas are tuned to 156.8 MHz. Though the two frequencies are close, having an AIS antenna for your AIS system, will optimize performance.

What is 3dB antenna?

A 2dB or 3dB gain antenna is the compromise in suburban and general settings. A 5dB gain antenna radiates more energy toward the horizon (compared to the 0, 2, and 3dB antennas) to reach radio communication sites that are further apart and less obstructed. Therefore, they are best used in flatlands and open areas.

Is higher or lower dBi better for antenna?

The higher the dBi number of the antenna, the higher the gain, but less of a broad field pattern, meaning that the signal strength will go further but in a narrower direction, as illustrated in the diagram below.

Does SWR matter for reception?

No. Assuming we’re talking about a characteristic impedance of 50 ohms, a 50 ohm resistor (otherwise known as a dummy load) will show a SWR of 1:1, although it will almost certainly perform very poorly as either a receive or transmit antenna.

What does dBi the most often used unit for antenna gain or directivity stand for?

What does dBi, the most often used unit for antenna gain (or directivity), stand for? An isotropic radiator is theoretically a point source (dimensionless), and therefore distributes the input power uniformly across the entire spherical volume surrounding it.

How is antenna gain in dB calculated?

1. 1 W = 1000 mW = 0 dB = 30 dBm.
2. 0 dBm = -30 dB = 0.001 W = 1 mW.
3. Gain of 10 dB = Gain of 10 dBi.
4. Antenna with a gain of 10 dBi = 10 dB = 7.85 dBd. Gain of half-wave diple antenna = 2.15 dBi = 0 dBd.