Hello, I need to set up a communication link between a shore station
and a dive boat that is at most 30nm (50 km) distance from the
shorestation (the shore station is on the beach i.e. there are no
obstacles between shore and ship)

Can somebody advice me if it is possible to do this with for exemple
2 Uniden Oceanus DSC VHF radioos and two 6 feet 6dB antennas? The Top
of the antenna would be about 16 feet aove sealevel on the boat and
about 30 feet on the shorestation?

Is there a better solution to assure the communiication . The radios
would be need for emergency cases)

Thanx fopr any input

wrote:
Hello, I need to set up a communication link between a shore station
and a dive boat that is at most 30nm (50 km) distance from the
shorestation (the shore station is on the beach i.e. there are no
obstacles between shore and ship)

Can somebody advice me if it is possible to do this with for exemple
2 Uniden Oceanus DSC VHF radioos and two 6 feet 6dB antennas? The Top
of the antenna would be about 16 feet aove sealevel on the boat and
about 30 feet on the shorestation?

Is there a better solution to assure the communiication . The radios
would be need for emergency cases)

Thanx fopr any input


Antenna heights are insufficient for
reliable communication over that
distance. The combined antenna heights
would need to be more than 400 feet for
marginal line-of-sight communication.

HF radio would work but is more
complicated and expensive.

The simplest solution may be a satellite
telephone system. Prices have come down
over the last few years.

Good luck.

Chuck

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In article . com, wrote:
Hello, I need to set up a communication link between a shore station
and a dive boat that is at most 30nm (50 km) distance from the
shorestation (the shore station is on the beach i.e. there are no
obstacles between shore and ship)

Can somebody advice me if it is possible to do this with for exemple
2 Uniden Oceanus DSC VHF radioos and two 6 feet 6dB antennas? The Top
of the antenna would be about 16 feet aove sealevel on the boat and
about 30 feet on the shorestation?

Is there a better solution to assure the communiication . The radios
would be need for emergency cases)

Thanx fopr any input

Standard distances suggest up to 111 kM for high antennas and high
power. I don't know whats legal for your shore station. I think
a 100 foot twin stacked yagis might work. I would use it only for backup.
If the boat moves, then a tall vertical is going to be iffy.
I don't have direct experiance, so test runs are mandantory.

greg

GregS wrote:


Standard distances suggest up to 111 kM for high antennas and high
power.

Power's not very important here. 111 kM
represents combined Rx + Tx antenna
heights of 3,000 feet!

I don't know whats legal for your shore
station. I think
a 100 foot twin stacked yagis might work.

Yagis have the same effect as increased
power. They can't make the signal bend
over the visual horizon.

I would use it only for backup.

Don't bother with the shore station even
as backup.

The boat ought to have a VHF in any case.

If the boat moves, then a tall vertical is going to be iffy.

Yes.


Chuck

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In article , Chuck wrote:
GregS wrote:


Standard distances suggest up to 111 kM for high antennas and high
power.

Power's not very important here. 111 kM
represents combined Rx + Tx antenna
heights of 3,000 feet!

I don't know whats legal for your shore
station. I think
a 100 foot twin stacked yagis might work.

Yagis have the same effect as increased
power. They can't make the signal bend
over the visual horizon.

I would use it only for backup.

Don't bother with the shore station even
as backup.

The boat ought to have a VHF in any case.

If the boat moves, then a tall vertical is going to be iffy.

Yes.

I used the reference at...
http://en.wikipedia.org/wiki/Marine_VHF_radio

Do you have a table for distances?

I always get about 60 miles from the cell phone up on Lake Erie. A
problem getting into Canada's system. I'm more familiar about talking
hundreds of miles through the dessert 2 meter amateur rigs.

greg


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GregS wrote:


I used the reference at...
http://en.wikipedia.org/wiki/Marine_VHF_radio


The 60 nm maximum range quoted is not
likely to be realized if one of the
antennas is virtually at sea level. An
antenna on a 1000 foot hill could do it.

The 5 nm range given for small boats is

Do you have a table for distances?

The range is ~ 1.4 times the square root
of the sum of the antenna heights. Now
you can verify some of your assertions.


I always get about 60 miles from the cell phone up on Lake Erie.

Sure you do.

A
problem getting into Canada's system. I'm more familiar about talking
hundreds of miles through the dessert 2 meter amateur rigs.


Sure thing.

Chuck

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On Tue, 05 Jun 2007 06:40:26 -0700, wrote:

Hello, I need to set up a communication link between a shore station
and a dive boat that is at most 30nm (50 km) distance from the
shorestation (the shore station is on the beach i.e. there are no
obstacles between shore and ship)

Can somebody advice me if it is possible to do this with for exemple
2 Uniden Oceanus DSC VHF radioos and two 6 feet 6dB antennas? The Top
of the antenna would be about 16 feet aove sealevel on the boat and
about 30 feet on the shorestation?

Is there a better solution to assure the communiication . The radios
would be need for emergency cases)

Thanx fopr any input

6 db antennas and 30 feet of shore station height are not going to get
the job done reliably.

The standard equation for VHF range is 1.15 * SQRT height, with the
two calculated ranges added together. The boat has a clculated range
of about 5 NM and the shore station about 7 NM, for a total reliable
range of 12 NM.

I'd go with 9 db antennas at each end and increase shore station
height to at least 100 feet. Even that will be marginal, and you will
need to use low loss coax cable at the shore station tower. A tower
mounted pre-amp/amplifier would be even better.

In article , Chuck wrote:
GregS wrote:


I used the reference at...
http://en.wikipedia.org/wiki/Marine_VHF_radio


The 60 nm maximum range quoted is not
likely to be realized if one of the
antennas is virtually at sea level. An
antenna on a 1000 foot hill could do it.

The 5 nm range given for small boats is

Do you have a table for distances?

The range is ~ 1.4 times the square root
of the sum of the antenna heights. Now
you can verify some of your assertions.


These calculations seem to be line of sight measurments, and I can agree with that.
Talking power or antenna types then would not matter. I see no calculation for
power in the formula.

greg




I always get about 60 miles from the cell phone up on Lake Erie.

Sure you do.

A
problem getting into Canada's system. I'm more familiar about talking
hundreds of miles through the dessert 2 meter amateur rigs.


Sure thing.

The problem I used to have, when I talked on the cell through Canada, I never got billed.
That was back in the analog days. The cell tower was over 50 miles away from the US shore.
I got very poor reception from that shore, but out 5-10 miles from shore, cell reception was steller.

Chuck wrote in news:1181052689_15255
@sp12lax.superfeed.net:

Antenna heights are insufficient for
reliable communication over that
distance. The combined antenna heights
would need to be more than 400 feet for
marginal line-of-sight communication.



I agree with Chuck. Marine radio is useless over-the-horizon more than
5% of optical line-of-sight.

Contact your local 2-way radio shop and ask them about installing TRUNK
RADIOS in both the shore installation and on the boat. The trunk radio
systems use very-high-up digital repeater stations that are widely
interconnected by computers that talk to the trunk radios, not unlike
what a Nextel iDen phone does, but on a much more powerful scale. These
trunk radio systems are shared by many diverse users, who rent service on
them for a pittance of what the entire trunk radio system costs.

Look in your local phone book under "2-way radio" or "trunk radio
systems" or "radio communications".

Professional communications, especially where life and limb might be in
danger, is well worth paying for. It's why the cops all use trunk radio
systems!

Larry
--
If electricity comes from electrons, does morality come from morons?

Chuck wrote in news:1181064796_15805
@sp12lax.superfeed.net:

An
antenna on a 1000 foot hill could do it.


You're never going to get a Shore Station Marine Radio license, which is
REQUIRED to operate a marine radio from shore with a 1000' tall antenna
that will cause interference in many conditions. VHF was never intended
for range.

Larry
--
If electricity comes from electrons, does morality come from morons?