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From: Larry DeMers (no email)
Date: Mon Aug 02 1999 - 08:30:26 EDT
Hi Norm,
wrote:
> In a message dated 7/29/99 12:47:49 PM Eastern Daylight Time,
> writes:
>
> <<
> ..Which improves my point..100W instead of 25W buys nothing but more charge
> time.
> >>
>
> Not completely true.
>
> Higher power does improve the range of a vhf signal, contrary to the
> conventional wisdom. The horizon does not cut off the signal sharply as they
> teach in school. Just ask any ham radio operator who is into vhf dx or look
> in the catalogs. The scuttlebut has it that the USCG uses 50 watt rigs, they
> certainly sound louder than other stations. Personally, if my life was on
> the line I'd want all the power I could get, legal or otherwise.
..Well, I am an ex-ham and work in VHF and Microwave everyday designing
clock systems for supercomputers etc. What you say is literally true, and is a
novelty when it happens. The effect is called tunneling, and it is responsible
for extremely long ranges when it works..but this is an atmospheric effect
whereby most of the radio energy is reflected back into a lower altitude, over
and over again, with the effect that California can talk with Hawaii as if they
are side by side. It was active on Superior this weekend in fact..but it is not
to be counted on, and 25 watts is highly effecive when it does work.
What you say is also true in another sense. The normal VHF signal does
experience some bending as it reaches the horizon, making the range extend
outwards another 5 miles maybe. But the problems would abound if **Everyone**
decided to be selfish and add a 100W transmitter to their boat. Their signals
woud interefer with a much larger number of nearby boats, and would effect
neighboring communities where a normal 25w signal from you would have died
off. Don't forget that neighboring community has it's share of boaters that want
to be heard also. Nobody wants their calls stepped on or interfered with. So the
only way to make it work is for **all** to pay attention to the same rules and
go by them. Anarchy on the radio does exist..it's called CB...and it is useless
for ordinary comms.
The CG, on Superior anyway uses the very highest hills available, then they
erect a 100 ft. tower, and put in a 100W repeater station. All of the Great
Lakes repeaters are able to simulcast the same signals if needed..this weekend,
on Lake Michigan, they were warning of a marker out of commision, and also an
overdue boat..we heard it on Superior's west end due to the repeaters. With this
installation, the CG does have radio comms over the entirety of Lake Superior
anyway, and I suspect all of the Great Lakes (correct me if this not right
please). They get their range from the height more than the power factor. Now
if it is storming out, the static and noise in the air will make that 100W
standout better, and is needed for that. But they are able to hear and transmit
to small vessels with 25W just because of their whole installation..height,
power and location.
Cheers!
Larry DeMers
s/v DeLaMer
>
>
> Norm
> S/V Bandersnatch
> Underway off the Georgia coast, northbound 6 Kts
>
> Norm
> S/V Bandersnatch
> 6 miles off the FL/GA coast, northbound 6 Kts
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