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Old 04-11-2016, 11:08 PM   #1
V ger
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Default VHF Channel Detecrion

NB

You are right to say that no one will monitor if or what channel you are tuned to. It is however a simple task. In order to provide optimum amplification the incoming signal is mixed with a frequency created by your radios internal oscillator to create a fixed intermediate frequency which is further amplified within your radio. This internal oscillator is controlled by the channel selector. Since few commercial radios have adequate shielding to prevent all emissions of this oscillator frequency anyone with a suitable receiver and a spectrum analyzer can tell exactly what channel you are monitoring.

Back when the BBC had a TV monopoly in England they used this technique to determine who was receiving their programing without paying the TV tax. They actually had vans with directional antennas that would drive around to find the none payers.
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Old 04-11-2016, 11:32 PM   #2
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Default Senior Moment Correction

Replace GMRS with FRS above
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Old 04-12-2016, 07:31 AM   #3
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Default portable radio

This will be my first year on the big lake, See a lot of talk about getting a radio . Any recommendations about what one to purchase and what details it should have, we have a pontoon boat and would want one that is portable. I look at all the ones on the Overton site, too many to chose from.
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Old 04-12-2016, 04:34 PM   #4
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Default Selecting a VHF radio

When selecting a VHF radio you will probably be best served by selecting a model from a major manufacturer such as Icom or Standard Horizon. Avoid store brands as they often fall short on service and parts availability over time. I have seen handhelds that had to thrown away because the batteries or chargers were no longer available. Often store brands are private labeled products by less than stellar manufactures. For use on the lake a basic model should fill all your needs and will be easy to use by a newbie boater and his friends who are also likely to be neophytes.

Points to consider with a hand held radio
Cell phones typically have a .3 watt output yet there are health concerns.
Hand held VHF radios typically have 5 0r 6 watt outputs with a selector switch for 1 watt. Always use the lowest setting you need to achieve your desired communication except for emergencies. This will also minimize interference with others on the same channel.
VHF communication is line of sight so range is largely dependent on antenna height. A rough approximation of the distance to the horizon is the square root of the observers eye or antenna height in feet. Thus if your eye is 4 feet above the water your horizon is approximately 2 miles away. If you are using an antenna 4 feet above the water to speak to someone with an antenna 9 feet above the water you will have effective communications up to about 5 miles ( 2 miles for your antenna + 3 miles for the 9 foot antenna).
The short antennas on handhelds also tend to limit range as they have a toroidal radiation pattern ( picture a donut with antenna in the middle of the hole). The longer antennas of a fixed radio have a flatter radiation pattern which projects more energy horizontally.
You must make sure you keep the batteries charged
Handhelds can be dropped overboard. Get a floating model or use a tether.
Waterproof models are obviously desirable especially since they can be used to call for help if your boat sinks.
No installation required and you can take it with you to your next boat.

Fixed radios require installation but with 25 watts of power and better antennas they out perform handhelds in every way. They cannot be dropped overboard. Mount the antenna as high and as far away from people as possible bearing in mind that you may need to pass under bridges. A laydown mount will help with bridge clearance.
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Old 04-12-2016, 07:50 PM   #5
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Default VHF Radios

Back in 1974 I bought a Modar VHF. At a cost of $1200. It was excellent. I didn't realize how excellent it was until a few years later when I bought my next boat and installed a Standard Horizon which cost about $275. You get what you pay for.

At the time, the range for a VHF with a wire antenna on a 35 foot mast was about 30-35 miles on "High Power" (@25 Watts.) The Modar had a range of about 40 miles with excellent reception. The Standard Horizon (eight years later) had a range of about 25-30 miles..with marginal reception quality. Just my experience... NB

EDIT: Those figures are for open ocean with no mountains in between.

YES, I do have some experience. As one of my fellow forum members recently said..I know everything:

Last edited by NoBozo; 04-12-2016 at 08:25 PM.
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Old 04-13-2016, 02:45 PM   #6
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Default VHF Features

Quote:
Originally Posted by RUGMAN View Post
This will be my first year on the big lake, See a lot of talk about getting a radio . Any recommendations about what one to purchase and what details it should have, we have a pontoon boat and would want one that is portable. I look at all the ones on the Overton site, too many to chose from.
I have always had great service from Raymarine. Not needed a lot, but handy to just walk in the door in Nashua and drop stuff off, get a call a day or two later to discuss solutions.

I always carried a VHF on my jetski. A Koozie on either end for protection and stored in a waterproof flotation bag. If you're not using it a lot and it's in a drawer, the Koozie protection is probably still a good idea.

Depends on your boat set up, but a charging system for whatever your boat has (12V or 110V shorepower) is convenient and probably prudent, especially if you want to leave it on board rather than taking it to the house to charge and then forgetting it there when you go boating. I think some handhelds may have a jack so you can connect to a remote speaker. I like that to be able to hear better over wind and engine noise. Even so, it is hard to hear when engines are running at cruise RPM, on plane. If you have to slow down to use your cell phone, the same will likely apply to the VHF.


Radio protocol: This is not a CB. It is a major piece of safety equipment. Adults only. Learn to call and respond properly, not "Hey good buddy, Jack, you out there?". Teach your crew how to make an emergency call and/or an assistance call, describing your vessel, location, nature of the emergency.
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