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braidiano
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5GHz link over the sea

Wed Nov 16, 2011 12:39 pm

Hi,

I'm planning a new link, that PtP 25Km total, but ~4.5 or 4.9 Km of the link are over water (sea).
I will use mimo parabolic (30 or 34 dBi gain) antennas and RB411AH device on both side at 5GHz, 40Mhz channel.
There will be a temperature difference between 10°C and 35-40°C from winter to summer.

I would optimize the link to get as more as bandiwith, I'm think of ~50Mbps.

Can you advice me about what kind of precautions should I take ?
I'm aware that will be signal fluttuations over the water. How can I mitigate it?

is NV2 good for that link?

Please let me know if I missed something on the scenario description.

thank you
 
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sadeghrafie
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Re: 5GHz link over the sea

Wed Nov 16, 2011 1:08 pm

Be aware that Wireless link over the seas may affect by reflection on the water surface (so multipathing of the signal), which will change in time, especially in the case of tidal waters, and possibly some ducting or even naval traffic in the area.
using 40 MHz is a good idea to increase Bandwidth but it may decrease the output power in long distance. You can try 40 MHz but whenever get in to trouble try 20 MHz and 15 MHz too. The solution for decrease multipath is using diversity instead of using Dual Pol Antenna.
This is my experience from 60 KM wireless Link all over the sea using Motorola PTP 500 Lite. :)
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braidiano
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Re: 5GHz link over the sea

Wed Nov 16, 2011 1:42 pm

ok, so about the multipathing of the signal, I know the the motorola, but it is over the budget of that link.
Do you know, or are you experieced, with a less expensive diversity antenna?

You can try 40 MHz but whenever get in to trouble try 20 MHz and 15 MHz too. The solution for decrease multipath is using diversity instead of using Dual Pol Antenna.
Maybe I can decrease at 20 or 15Mhz, and will use 2 link in boding, to obtain the bandwith.
 
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sadeghrafie
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Re: 5GHz link over the sea

Wed Nov 16, 2011 4:53 pm

It's is not good to talk about using diversity now while you don't have any calculation of the link or not try the link till now.
I recommend you to use some link planner. I attached two files about my project. one before using diversity and the other after that. You can use Motorola Link planner to open them. It also works with Google Earth.
noticed that this is all about Motorola not any other brand, but using Motorola Link Planner is useful for simulating I think. :)

I hope Mikrotik release software like Motorola.

You may read some useful source like CWNP books. There are some characteristic such as :

Visual LOS
RF LOS
The Fresnel Zone
Intentional Radiator
EIRP
Wave propagation


Which are important to a wireless link.
You do not have the required permissions to view the files attached to this post.
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JorgeAmaral
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Re: 5GHz link over the sea

Thu Nov 17, 2011 4:22 am

Hi,

I'm planning a new link, that PtP 25Km total, but ~4.5 or 4.9 Km of the link are over water (sea).
I will use mimo parabolic (30 or 34 dBi gain) antennas and RB411AH device on both side at 5GHz, 40Mhz channel.
There will be a temperature difference between 10°C and 35-40°C from winter to summer.

I would optimize the link to get as more as bandiwith, I'm think of ~50Mbps.

Can you advice me about what kind of precautions should I take ?
I'm aware that will be signal fluttuations over the water. How can I mitigate it?

is NV2 good for that link?

Please let me know if I missed something on the scenario description.

thank you
I would use antennas with less gain (23dB) and when installing them set it´s uptilt to the point of -3dB. For a 23dB typical antenna it´s beamwidth is 10º, so you uptilt your antenna 5º.

Another approach is to set 2 antennas on the same mast with +/- 10 meters of vertical separation and the -3dB uptilt connected to a R52Hn radio.

I never tried NV2 over water.

Kindly regards,
 
braidiano
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Re: 5GHz link over the sea

Thu Nov 17, 2011 10:43 am

It's is not good to talk about using diversity now while you don't have any calculation of the link or not try the link till now.
I recommend you to use some link planner. I attached two files about my project. one before using diversity and the other after that. You can use Motorola Link planner to open them. It also works with Google Earth.
noticed that this is all about Motorola not any other brand, but using Motorola Link Planner is useful for simulating I think. :)

I hope Mikrotik release software like Motorola.

You may read some useful source like CWNP books. There are some characteristic such as :

Visual LOS
RF LOS
The Fresnel Zone
Intentional Radiator
EIRP
Wave propagation

Which are important to a wireless link.
Thank you!
I usually use Radio Mobile, but I will try the Motorola one.
I would use antennas with less gain (23dB) and when installing them set it´s uptilt to the point of -3dB. For a 23dB typical antenna it´s beamwidth is 10º, so you uptilt your antenna 5º.

Another approach is to set 2 antennas on the same mast with +/- 10 meters of vertical separation and the -3dB uptilt connected to a R52Hn radio.
What kind of antenna do you mean? Parablic ones?
 
rjscomms
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Re: 5GHz link over the sea

Thu Nov 17, 2011 11:28 pm

Hello,

my 2 cents worth....use vertical polarisation not horizontal.

A horizontal signal will get absorbed when traversing a body of water.

As for modulation methods, I have not had the chance to try.

Good luck.
 
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mramos
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Re: 5GHz link over the sea

Fri Nov 18, 2011 2:05 am

Hi ...

Avoid different antenna heights, I mean, or 10m each side ... or something above 40m each side.

Under calm surface conditions and no wind there's a big chance to exist sort of spray layer ~5 to 8m above sea surface.

Under rough sea and windy days, this layer spread but exists around 30 ... 40m above sea surface.

So this spray is always there and if one side is 5m above sea and the other 40 ... there's a good chance that the lower antenna signal propagate inside the duct and the higher reflected above by the same layer.

And more: ducting may be a tool but depending on ... can bring to your area signals that are tenths or hundred km away with good strenght.

Regards;
Marcus Ramos
Electronics Technician
(Microwave HW, RF, antennas, propagation)
S.Paulo - Brazil
 
braidiano
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Re: 5GHz link over the sea

Sun Nov 20, 2011 2:34 pm

thank you guys! I'll report how it will go :D

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