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List all topics --> Cruising & Marine Navigation Forum --> VHS Radio
Anonymous user
06 November 2006 14:14:16 |
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VHS Radio
GET ONE BEFORE YOU NEXT GO OUT ON YOUR BOAT!
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Anonymous user
07 November 2006 16:01:32 |
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Re: VHS Radio
Never leave home or port with out one!
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Anonymous user
09 August 2007 21:56:46 |
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Re: VHS Radio
Please forgive my ignorance but don't you all mean VHF radio?
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lyonsden
18 November 2007 23:07:39 |
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Joined: October 2007
Location: Vancouver, Canada
Posts: 3
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Re: VHS Radio
I thought something looked funny! :)
Ya, I am getting one in my stocking this year! I am a new boat owner who has neglected to purchace one yet. Thinking tunes and woman first! :) I went a few times this summer without one and
now I feel sick even thinking I didn't have one. Especially going down the river a bit to get to the Georgia Strait here in Vancouver.
____________________
http://www.choice-marine-supplies.com/
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Anonymous user
27 August 2008 09:39:01 |
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VHF Radio
Very high frequency (VHF) is the radio frequency range from 30 MHz to 300 MHz. Frequencies immediately below VHF are denoted High frequency (HF), and the next higher frequencies are known as Ultra high frequency (UHF).
Common uses for VHF are FM radio broadcast, television broadcast, land mobile stations (emergency, business, and military), Amateur Radio, marine communications, air traffic control communications and air navigation systems (VOR in particular).
VHF propagation characteristics are ideal for short-distance terrestrial communication, with a range generally somewhat farther than line-of-sight from the transmitter (see formula below). Unlike high frequencies (HF), the ionosphere does not usually reflect VHF radio and thus transmissions are restricted to the local area (and don't interfere with transmissions thousands of kilometres away). VHF is also less affected by atmospheric noise and interference from electrical equipment than lower frequencies. Whilst it is more easily blocked by land features than HF and lower frequencies, it is less bothered by buildings and other less substantial objects than UHF frequencies.
Two unusual propagation conditions can allow much farther range than normal. The first, tropospheric ducting, can occur in front of and parallel to an advancing cold weather front, especially if there is a marked difference in humidities between the cold and warm air masses. A duct can form approximately 250 km (155 mi) in advance of the cold front, much like a ventilation duct in a building, and VHF radio frequencies can travel along inside the duct, bending or refracting, for hundreds of kilometers. For example, a 50 watt Amateur FM transmitter at 146 MHz can talk from Chicago, to Joplin, Missouri, directly, and to Austin, Texas, through a repeater. In a July 2006 incident, a NOAA Weather Radio transmitter in north central Wisconsin was blocking out local transmitters in west central Michigan, quite far out of its normal range. The second type, much more rare, is called Sporadic E, referring to the E-layer of the ionosphere. A sunspot eruption can pelt the Earth's upper atmosphere with charged particles, which may allow the formation of an ionized "patch" dense enough to reflect back VHF frequencies the same way HF frequencies are usually reflected (skywave).
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