200km at sea level AP/Bridge... is that possible?

[AndreC]

Hi,
I have a challenge here;

I need to interconnect 3 islands together.

The main island is where we had our ISP and also our Domain Controller Server.

The other 2 remote islands are located at about 200km away.
The tallest mountain we have is not nearly enough to get a line of sight to any of the other islands but at least no obstructions.

What radio(s) +Antenna would allow me to connect time at a speed of 5 mbps ?

I've read that some italians have done similar with 304 km ... but i believe they had line-of-sights.

Please any suggestions would be appreciated.

Thanks

[WHT]

If you don't have a direct line of sight, its not going to work. 900 Mhz has some non-line of sight capability, but that's for foliage and trees and some hills.

If...IF....you has 300 meter peaks at BOTH ends, you could make the path with only a few dB above the minimum receiver sensitivity. But you would have perhaps several hours per day downtime.

But..BUT....You're shooting over water and that even more problematic. Circular polarized 22 dBi gain antennas might work.

[AndreC]

Hi,

How can I calculate the tower elevation requirement for both ends?

Distance is 200km

Also require the type of antenna (dish, polarity,..) and dB gain?


Thanks
Andre

[WHT]

PM me with some GPS numbers

[WHT]

I didn't even bother to run a plot.

Yap tower elevation is only 420 feet + I guess about 50 ft. self supporting tower.

Falalop is about 120 miles east and the highest point is only 40 ft above sea level.

Looks like you're out of luck.

BTW...what happened to that 1,000 ft. LORAN tower they decommissioned about twenty years ago?

[AndreC]

Well, just made some calls about this and the story is that when they moved to Yap proper, this tower was dismantled.

It would be nice to be able to put another one.

If we manage to get assistance from outside, what kind of height you believe would be sufficient on the Falalop side?

Would we require also to raise much the antenna here in Yap as well?

How can we calculate the minimum and recommended height for both towers?

Thanks

[WHT]

Here's the formula for calculating optical line of sight.

Distance to the visual horizon = [(square root of tower #1 height) X 1.1] + [(square root of tower #2 height) X 1.1]

If tower 1 is 100 ft, horizon is 11 miles away
If tower 2 is 400 ft, horizon is 22 miles away.
Therefore the top of tower 1 can see top of tower 2 at 33 miles away.

If you case, we'll use a few tower examples.

Tower 1 is 3,500 ft, so its 65 miles to horizon.
Tower 2 is 3,500 ft, so its 65 miles to horizon.
So you have a 130 miles distance.

Tower 1 is 5.00 ft, so its 78 miles to horizon.
Tower 2 is 1,500 ft, so its 42 miles to horizon.
So you have a 120 miles distance.

Of course this leaves no room for any Fresnel clearance, which would require even higher antennas.

Perhaps you might want to consider over-the-horizon (tropospheric scatter) microwave radio relay, which be far beyond the scope of explanation at this point.

[AndreC]

Thanks

I guess that building tower that big and typhoon proof might be a little too big as a project unless we receive lot's of funding...

As for the other option you mentioned, what kind of price range would we be talking about? would this allow bandwidth of 5mbps in all weather conditions?

Thanks

PS: I just bricked my NS2 trying to downgrade from OSWAVE and lost power while waiting for the 240sec required... i'm in trouble now...

[WHT]

what kind of price range would we be talking about?

Two million dollars would not surprise me.

i'm in trouble now

Yes....