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amatteo78
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about 50Km link p2p

Fri Jun 01, 2007 10:29 am

Hello,

next month I will made a link p2p about 50Km, first station is about on building 15mt from ground and the ground is about 150mt on level sea, the second station is on tower about 15mt from ground but it is about 1500mt on level sea, two side are in LOS.

I think use a couple of RB112, R52 and Grid 29dBi, is it possibile this link ?? if yes how db I will obtain ?? and how Mbit/sec ??

Thank you so much

Matteo
 
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Re: about 50Km link p2p

Fri Jun 01, 2007 12:39 pm

i suggest you go with RB532, this is what my experience says if you need good throughput.
 
amatteo78
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Re: about 50Km link p2p

Fri Jun 01, 2007 12:42 pm

thank you so much to your reply, to alignament two antenna what are right way ??
thanks

Mat
 
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Re: about 50Km link p2p

Sun Jun 10, 2007 5:27 am

Please keep us posted about how this link went, we are currently deploying a 52Km one, having a hard time aligning those 4ft dishes...

Any ideas, technics, method to align those narrow beam big buckets...


Best

Jorge
 
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Re: about 50Km link p2p

Sun Jun 10, 2007 5:52 am

Hi,

Well, Mikrotik have "alignment" Mode. I use this and too much patience. We have links with 20Km and 32dbi Disc with 32Mbps througput.

Regards,
Fran.
 
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Re: about 50Km link p2p

Sun Jun 10, 2007 5:28 pm

Thks for sharing Frank.

That´s the way we have been trying but no luck, we just installed those last week, we will try again this week with one guy on each tower; we were usng googleearth , gps , compass to pre-align dish on point A and we were only moving dish on point B but I guess point A was not properly aimed. Those dishes has 4º of beam width and for a 52 Km , 1/4" here means probably houndreds pf yards there .... we´ll see.

Any more ideas guys ....

Best

Jorge Boardman
 
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Re: about 50Km link p2p

Mon Jun 11, 2007 12:29 am

GPS is useless for antenna alignment - stick with the compass, and make sure you have taken the specific magnetic declination for your area into account...
 
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Re: about 50Km link p2p

Wed Jun 13, 2007 9:13 pm

GPS is useless for antenna alignment - stick with the compass, and make sure you have taken the specific magnetic declination for your area into account...
Well, actually not so useless.

There are equipment that surpass any interference my mean of GPS, so, GPS is very very usefull, actually.

Regards.
 
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Re: about 50Km link p2p

Wed Jun 13, 2007 9:45 pm

This is something I have used in the past and it might help. Pick a point on a hill in line between the two endpoints using software to get the GPS coords. Set up a temporary low gain grid antenna transmitter pointed toward the closest endpoint at this calculated position. Align that endpoint to the temporary transmitter. Align the far endpoint while leaving the first one alone until it is linked. Did any of that make sense.......... :-)
 
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Re: about 50Km link p2p

Wed Jun 13, 2007 10:02 pm

 
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Re: about 50Km link p2p

Thu Jun 14, 2007 1:02 am

GPS is useless for antenna alignment - stick with the compass, and make sure you have taken the specific magnetic declination for your area into account...
Well, actually not so useless.

There are equipment that surpass any interference my mean of GPS, so, GPS is very very usefull, actually.

Regards.
Well - not entirely useless, except for plotting co-ordinates - and these are essential without having to mention.
As far as using a GPS for alignment (compass function)... forget it, unless it's an expensive magnetic compass type.
 
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Re: about 50Km link p2p

Fri Jun 15, 2007 2:08 am

Thks for sharing Frank.

That´s the way we have been trying but no luck, we just installed those last week, we will try again this week with one guy on each tower; we were usng googleearth , gps , compass to pre-align dish on point A and we were only moving dish on point B but I guess point A was not properly aimed. Those dishes has 4º of beam width and for a 52 Km , 1/4" here means probably houndreds pf yards there .... we´ll see.

Any more ideas guys ....

Best

Jorge Boardman
Well, Here appears to be a success story;

After a few hours, a lot of patience with a guy on each tower, struggling with the aiming of the 4ft. dishes, the link was a success, 54Kms, linked at 24-36Megs, with a TCP throughput of around 15M-16M UP and DN. -78dBm Signal Strength, 21-22 SNR, 70-71 CCQ.

The link has been up and running for 25 hours till now w/o an issue.

Nstreme all defaults, XR5 working @ 5180Mhz , Default TX power.

Thks to all the guys the helped and pointed us in the right direction.

Best

Jorge Boardman
 
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Re: about 50Km link p2p

Sat Jun 30, 2007 10:01 am

Dear All

I got to read across tha lot many of you ae facing proble with links with distnaces more then 30 KM .. We have deployments of upto 60km and that too in ease. At all the locations I have used RB/112 and NMP 8602. Antenna used are 24db Andrews / Hyperlan etc and a customised 30db antenna on wire mesh dish . we are getting the actual thruput of 4-8mb Duplex on each link but in wireless registration its 48mbps. Just keep one thing to give the height if the MSL is same at both locations. I palnfor 45 mtrs height everywhere as here we have trees upto 27 mtrs .

If any problem can bet back to me on vishalchadha@hotmail.com

Vishal Chadha
 
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Re: about 50Km link p2p

Sat Jun 30, 2007 4:08 pm

Success in long haul links depends to a very large extent where you are located in the world.

Some areas see very little fade, others see a lot.

We started doing 50km links with MT over four years ago. We only have three of the orignal six still running, the rest of them are now on 6gig licensed wireless with spatial diversity and use protected, hot-standby radios.

For example, on 50km north-south links close to Toronto, we see a combination of up to 50dB of nightime fade coupled with a 30dB rise in our noise floor due to ducting. The sum of these effects can destroy a connection up for half an hour at a time around dawn. "Fade season" here typically lasts for three weeks in the Spring, and then comes back for another couple of weeks in the Fall. Not good!

And that is using 12' dishes and 26dB radios!!

The only solution to this problem is spatial diversity, but unfortunatly MT has so far been deaf to all requests to support diversity.

You can create really long links very easily, but the real test is how they survive thoughout the year, and what kind of downtime you will see in your "worst month". There are some very good link calculators that take into account your geographical location and give you uptime calculations for the whole year, and also give "worst month" uptime which can be substantially different.

Just a word of caution, your mileage will vary. If in doubt, talk to your local 6gig long-line licensed operators about what kind of conditions and challenges they face. That information will help you a lot when designing 5gig links using MT.

George
 
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Re: about 50Km link p2p

Sat Jun 30, 2007 7:41 pm

Well thanks a lot, that info may become handy for sure...

Best

Jorge Boardman
 
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Re: about 50Km link p2p

Sat Jun 30, 2007 11:31 pm

There are some very good link calculators that take into account your geographical location and give you uptime calculations for the whole year, and also give "worst month" uptime which can be substantially different.
Any calkulators like this that is available online?
 
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Re: about 50Km link p2p

Sat Jun 30, 2007 11:43 pm

Not sure what is available for online use that takes location into account.

I still use an Excel-based Orthogon link calculator that is a couple of years old. It allows you to input the lat/long for each end of the link, and calculates for that specific geography. In addition, it gives you reliability predictions for whole year and worst month. Seems to correlate very well to actual conditions.

You see very large changes in predicted reliability as you change lat/longs...

George
 
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Re: about 50Km link p2p

Sun Jul 01, 2007 8:13 am

After a few hours, a lot of patience with a guy on each tower, struggling with the aiming of the 4ft. dishes, the link was a success, 54Kms, linked at 24-36Megs, with a TCP throughput of around 15M-16M UP and DN. -78dBm Signal Strength, 21-22 SNR, 70-71 CCQ.
-78dBm seems rather low for 50 k and 4ft dishes with an XR5, we have a 20km link with far less favourable link path (hill midway impinges on fresnel a bit, heights ASL 90/200 mtrs) using two RIC/522's and SR5 we get -57dBm, no 4ft be-hemoth dishes required!

cheers

Bill
Any ideas on how to improve this?

- LoS?, we are positive it is clean, there is a 2.1 link from same point to same point 50ft below ours on each tower.

- Alignment? well we have climbed those towers three times by now and spent like two hours each time trying to get better values w/o success, our "best" has been -75dBm signal with a 23-26 SNR. The antenna patter do not show any side lobes like in grid antennas so we are not "peaking" at a side lobe ...

- Switching from H pol to V pol ? We have done that one... One our Gabriel 4 footers the installer can "turn" de RF feeder we have tried that one ... first on one side of the link then fine-tune it on the other side of the link.

- What´s seems odd to me is the fact thse 4ft dishes are "designed" to operate on 5.4-5.8 Ghz and our best values are in 5.1-5.2 Ghz ... seems odd to me ... (any explanation for this?)

- Tx power on the XR5? We have tried several combinations almost same results.

Actually we are looking for a way to improve this values since our link has not been very stable specially during heavy rain storms...

Best

Jorge
 
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Re: about 50Km link p2p

Mon Jul 02, 2007 10:05 am

I would also suggest using a tool like Radio Mobile (free sw) to help calculate the best height AGL for your antennas. Getting the antennas on either side at the correct height is important to ensure each is within the other's fresnel zone. A few meters change in height on either side can make a huge difference in signal strength.
 
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Re: about 50Km link p2p

Mon Jul 02, 2007 10:42 am

I'll go through Radio Mobile learning curve.... thks for the advice's.

Jorge
 
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Re: about 50Km link p2p

Mon Jul 02, 2007 11:07 am

If you need any help - feel free to ask... I've gotten fairly proficient in RMW over the past year of using it, and it's almost always helped me improving the quality of my links...

Pre-prepared antenna pattern files and free topographical data can be a bit of a schlep to find on the web, but there are some good 'Getting started' guides like here:
http://www.pizon.org/radio-mobile-tutorial/index.html

and the main site is here:
http://www.cplus.org/rmw/english1.html

Although topographical data can be downloaded automatically by the software when it's needed, it's best to download it and work from your hard drive:
ftp://e0srp01u.ecs.nasa.gov/srtm/version2/SRTM3/
 
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Re: about 50Km link p2p

Tue Jul 10, 2007 3:54 am

If you need any help - feel free to ask... I've gotten fairly proficient in RMW over the past year of using it, and it's almost always helped me improving the quality of my links...

Pre-prepared antenna pattern files and free topographical data can be a bit of a schlep to find on the web, but there are some good 'Getting started' guides like here:
http://www.pizon.org/radio-mobile-tutorial/index.html

and the main site is here:
http://www.cplus.org/rmw/english1.html

Although topographical data can be downloaded automatically by the software when it's needed, it's best to download it and work from your hard drive:
ftp://e0srp01u.ecs.nasa.gov/srtm/version2/SRTM3/

Thks a lot, this info is realling helpping me.

Best

Jorge

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