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Author Topic:   Handheld VHF
reeltime2 posted 06-28-2000 08:42 AM ET (US)   Profile for reeltime2   Send Email to reeltime2  
I think I have dicided to get a handheld vhf (Raytheon Ray 100) versus a permanant mount. My question is does anyone know what the range diferance is between a 5 wt. handheld and a 25 wt. permanent mount? Can I assume there is 5 times the power so it will have 5 times the range? I usualy fish about 1-5 miles off shore here in south florida(in my 15 ft s.s.) does anyone think the handheld will work for me?
Thanks in advance,
Rick
jimh posted 06-28-2000 10:39 AM ET (US)     Profile for jimh  Send Email to jimh     
The range of VHF radio transmission is mainly constrained by the heights of the antennas involved in the circuit.

Higher power is handy to over ride interference on the channel, but it does not extend one's range in the linear fashion you suggest. That is, a 25 W transmitter does not have five times the range of a 5 W transmitter.

When calculating the range between VHF stations, the distance from each antenna to the "radio horizon" is calculated, then the two are added together to get the maximum path.

The formula is approximately:

Range (in Miles) = 1.2 x SQRT(Height) (in feet)

In the case of calling the Coast Guard, their antenna will be several hundred feet in the air and its radio horizon will be the principal determinant of the range at which they can hear you.

As you see from the formula, even doubling the height of your antenna only increases its range by a factor of about 1.4.

At the comparatively short ranges of marine VHF transmission, 5 W is more than sufficient to produce a readable signal, absent interference from other stations.

The biggest drawback to handheld transmitters is their battery life. I would be certain to have an external power cord so that I could operate the handheld transmitter from the boat's 12Vdc battery. This may require some adaptation, as often these radios use a supply voltage of less than 12-Volts.

--jimh

frank posted 07-17-2000 01:09 AM ET (US)     Profile for frank  Send Email to frank     
i have a ray 100 like the one you intend to purchase. i love it -rember if you really need to call the coast guard you may not have electrical power for one reason or another. the ray 100 will last all day if you are just monotoring.(not transmitting) the nicad batteries are very powerful. and it comes with a seperate battery tray,so you can have emergency back up power,say if you forgot to charge the standard pack. i love the radio and highly recommend it. >>cape cod
Ed Stone posted 08-18-2000 08:15 AM ET (US)     Profile for Ed Stone  Send Email to Ed Stone     
While doing a radio check to TOWBOAT
They said I sounded broken up,and could
barely hear me.Could the problem be
hazy conditions,24 miles out,bad connections
at the antenna?
Thanks,Ed Stone
triblet posted 08-18-2000 10:23 AM ET (US)     Profile for triblet  Send Email to triblet     
The possibility of having a dead battery
is why I carry a console mount (Standard
Spectrum) and handheld (Standard HX350S)
and the adapter to run the handheld from
the 8' whip. And spare batteries for the
handheld. All on a Montauk.

24 miles is marginal for a console mount
and 8' whip. If it were bad connections
at the antenna, it would sound bad closer
in too.

Chuck Tribolet

triblet posted 08-18-2000 10:29 AM ET (US)     Profile for triblet  Send Email to triblet     
And on the subject of range difference:
A couple of weeks ago I had the Montauk
down in the north end of Carmel Bay when
a buddy of mine started calling Vessel
Assist. He was about a mile away out of
gas in his inflatable. I could hear him
on his handheld fine. VA, five miles away
in Monterey, couldn't. They could hear my
console mount though. I ended up towing
him in.

This prompted another inflatatble buddy to
put an 8' whip on the boat for his handheld.
He says he hears a LOT more traffic now.

Antenna counts.

Chuck Tribolet

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