dconnwb
join:2006-08-21
| 65 mile over-the-sea possible?
Hi all,
Does anything think it would be possible to have a 65 mile (about 100km) link between two mountains with the sea in between?
I know that there would be a 50 foot or so loss due to curvature of the earth but that doesn't sound like a problem. The huge distance may be a problem and also I'm not sure if data can even travel over water/waves (I think I remember reading that data gets scrambled by reflections from water?)
thanks for any replies!
Derek |
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LLigetfa
join:2006-05-15
Fort Frances, ON | I think you misplaced the decimal point in your calculations. You would need 500 feet elevation at each end to overcome the curvature. |
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PersComp
Premium
join:2005-08-17
Cayce, SC | reply to dconnwb
With the very tight beam and the height required for that distance, would multi-pathing over water really be an issue?
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Are these instructions or corrections??? |
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Believer
join:2002-07-04
Baltimore, MD
| reply to dconnwb
Go with an Orthogon and 6ft dishes on each side. You'll spend 94% of your time in the top two modulations. That's assuming you are at least 1000 ft above the water on the mountain top.
Since the 6ft dishes will be your biggest expense, you could try it with Mikrotik and SR-5s first and see how the link performs. Just be sure to get the dual-pol dishes in case you do go with Orthogon, as with Orthogon it's the dual-polarity the makes the links so solid.
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Comtrain Certified Tower Climber |
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dconnwb
join:2006-08-21 | reply to LLigetfa
I think its only around 50 feet just to overcome the curvature isn't it? 8 inches per mile so (65 [miles] * 8 [inches]) / 12 = 43 feet?
Derek |
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LLigetfa
join:2006-05-15
Fort Frances, ON
| Here is the long form but I have not tried it.
»www.zytrax.com/tech/wireless/calc.htm?pf=yes
I rely on RM to do it for me. Give us the GPS coords for the two sides and someone is sure to run it through RM for you.
What regulatory domain are these in for max EIRP calculations? Here is a success story from Ecuador.
»57 KM link with High gain low cost CPE
I attached an example of an impossible link from two of my towers. |
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lutful
Premium
join:2005-06-16
Ottawa, ON
 ·TekSavvy Solutions..
| reply to dconnwb
Since this post, I have discovered that there are many 100km+ "inter-island" links in Indonesia, Maldives and Seychelles. »Current longest 5.8Ghz OFDM link?
Most links use BPSK or QPSK modulation so data rate is less than 10Mbps. Due to strong winds, they use giant C-band grid antennas with 5Ghz circular polarization feed.
Kindly post co-ordiantes for RM analysis. I will also lookup the "average wave height" that you should add to tower height.
Finally, such links require at least 30dBm EIRP, so we need to check regulatory domain too.  |
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LLigetfa
join:2006-05-15
Fort Frances, ON
| Here is a story of a 125 mile link.
»www.unwiredadventures.com/unwire···sho.html
If they had bothered to take the sag out of the feed arm, they could have had more fade margin.  |
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lutful
Premium
join:2005-06-16
Ottawa, ON
·TekSavvy Solutions..
1 edit | The current record 279km link in Venezuela seems to be built by experts who also documented everything very well. »RM plot for 279km 2.4Ghz link
Edit: diffraction discussion deserves another thread. |
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