VHF Range Question

[Phantom]

Originally Posted by pjard

... I was once in Smith Cove and on a handheld VHF and heard a fishing guide who was in Meredith Bay

Comment#1
Also, keep in mind that you will hear (Receive) chatter from all over the Lake on your handheld, but you will not (in most cases) be able to transmit back due to the distance/ power limitations of the handheld.

Comment#2
I have a 4' Shakespeare mounted on a 26' bow rider (i.e. not high up on an arch or anything) & have absolutely no problems xmitting/receiving across 90% of the Lake. We routinely talk from Meredith or Center Harbor with my daughter in WAM. The sometimes sketchy distance would be Center Harbor to the Alton Public docks area. Mount Major gets in the way for that !



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[Descant]

Line of sight seems to be more a simplification than a true descriptor in this case. There's a good article on en.wikipedia.org/wiki/Line-of-sight_propagation, but it boils down to radio range (miles) is 1.23 x the square root of the altitude (feet), which is also what sticks in my mind from government issue electronics classes in sliderule days. Something that could be easily and quickly calculated in your head. This gets modified by antenna type (broadcast or focused), power, etc. as discussed earlier as well as frequency. Think of the radio signal as a lobe or tear drop shape. You could be in the center or on the edge of the lobe and moving a little up, down or sideways may improve or degrade the signal.

[Rich]

yes, and the height of your antenna (and type of antenna) will greatly affect your range.

Just getting the antenna up 6 or 8 feet more will make a difference. So if you have a small boat, get the antenna as high as possible. They even sell antenna extensions to help with the height. Some people don't like the extensions as they may mean you need to lower the antenna when going under a bridge, etc. but if you want better radio range, the higher the antenna, the longer distance you will be able to communicate.

Some antennas have more 'gain' than others. The higher the gain 'gain' basically means that the antenna focuses the energy more than one with a lower gain. Higher gain antennas tend to focus the radio energy to the horizon (and works both for receiving and well as transmitting), but on a boat, the higher the gain, the more fading you can get as the boat rocks. This may be more of a problem on the ocean with swells and such, but just keep it in mind. A high gain antenna may be bad for a sailboat as it heels over a lot, but not so bad for a power boat as they tend not to spend much time on their side.

This page at Westmarine has a pretty good description along with good illustrations to demonstrate what is going on. It also has a good table that illustrates how much height can affect your radio range:
http://www.westmarine.com/WestAdviso...-a-VHF-Antenna