Hi,

Can you share aligning tips for a 52Kms PtP link ...

Pointing the dishes ... ideas how to start how to "find" the narrow beam on such a long link.

Settings on the routerOS start in aligning mode or just move the dishes over and over and wait until the radios get registered to fine tune them?

Please advice.


Best

Jorge Boardman
Greetings from Nuevo Laredo Mexico

Expand on what hardware you are using. Radios, antennas, tower heights both AGL and AMSL on both sides and frequencies. Also GPS coordinates if you have them. A 52km link is something that takes some preplanning and I'm not sure your issue isn't LOS, fresnel, etc.

Expand on what hardware you are using. Radios, antennas, tower heights both AGL and AMSL on both sides and frequencies. Also GPS coordinates if you have them. A 52km link is something that takes some preplanning and I'm not sure your issue isn't LOS, fresnel, etc.

Ok thks for the reply, here's the info you are asking, I am being very specific; maybe this info could help others in the future:

* Antennas: General Dynamics (Gabriel) model HQFD4-52, 5.25 Dual Pol. QuickFire 4', 34.3-34.9 dBi, 5.25 - 5.85 GHz, FtB ratio 52.
* Wireless cards: Ubiquiti XR5
* Mobo's: Routerboard 532A
* OS: RouterOS running WDS w/nstreme all dynamic and default. Bench tested.
* Surge suppressors: Hyperlink 0-6Ghz
* Pigtails from the card to suppressor: 9" MMCX to N
* Pigtails from the surge suppressor to antennas: wisp-router 6ft N on both sides.
* Enclosure Pacific Wireless Die Cast Aluminum
* Power supplies Pacific Wireless 48Vdc PoE
* Site A: 27°32'11.03"N , 99°28'18.30"W , Elevation = 494 ft , Antenna 100 ft AGL
* Site B: 27°23'50.30"N , 98°58'52.22"W , Elevation = 880 ft , Antenna 250 ft AGL
* Total Distance 31.68 miles (50.82 Km)

* Antenna Tilt Calculator Results:



Height of antenna A (AGL) : 30.480 meters (100.000 feet)
Ground elevation at A (AMSL) : 150.571 meters (494.000 feet)
Antenna A total elevation : 181.051 meters (594.000 feet)
Height of antenna B (AGL) : 76.200 meters (250.000 feet)
Ground elevation at A (AMSL) : 268.224 meters (880.000 feet)
Antenna B total elevation : 344.424 meters (1130.000 feet)
K factor : 1.330
Total path distance : 50.820 kilometers (31.578 miles)
Antenna A to B tilt : -0.002 degrees (-0.000 radians) (downward tilt)
Antenna B to A tilt : -0.371 degrees (-0.006 radians) (downward tilt)

* Wireless Network Link Analysis Results:



Transmitter frequency : 5800.000 MHz (5.800 GHz)
Wavelength : 5.169 centimeters (2.035 inches)
Transmitter RF power output : 28.000 dBm (630.957 milliwatts)
Transmit cable type : Times Microwave LMR-400
Transmit cable length : 1.829 feet (6.000 meters)
Total transmit cable loss : 0.649 dB (0.108 dB/foot 0.355 dB/meter)
Transmit antenna gain : 34.5 dBi
RF input power to the antenna : 27.351 dBm (543.375 milliwatts)
Receive cable type : Times Microwave LMR-400
Receive cable length : 1.829 feet (6.000 meters)
Total receive cable loss : 0.649 dB (0.108 dB/foot 0.355 dB/meter)
Receive antenna gain : 34.5 dBi
Received power level : -46.138 dBm (1103.048 µV)
Receiver's threshold : -74.000 dBm (44.615 µV)
Fade margin : 27.862 dB Very good link.
Probability of outage : 0.1 %
Total free space path loss : 141.839253085546 dBi over a path length of 50.820 kilometers (31.578 miles)
Peak transmitted EIRP : 61.851 dBm (1531341.409 mW)

* According to Motorola's Link Estimator it shows fresnel and LoS are OK



Calculations : were obtained from : http://www.electro-comm.com/rfcalculations.html
Motorola Link estimator: Google for it.

Antennas specs: http://www.tessco.com/products/displayP ... ventPage=4

Google earth image of the link:



Hope this info help others and hopefully somebody can help us aiming these babies ...

Best Regards
Jorge

Antenna A is only 100' in the middle of what looks like a city. Do you have line of sight out of the city with no obstructions?

Antenna A is only 100' in the middle of what looks like a city. Do you have line of sight out of the city with no obstructions?

Yes, no obstruction. The Site A is almost at the border of the city with short building in the area, and on the path direction practically next door there is an airport, an the antenna is way above the hangars. The antenna tower is located at the highest place of the city, around 80' the average.

Best

Jorge

Have you tried the link at a short distance to make sure they link in that scenario?

I have found the best way to align antennas on a long link is to use a compass. You have the GPS co-ordinates, so can work out the azimuth. An inclinometer will give you the correct downtilt.

We have a high 'first hit' success rate on 40-50km links using these tools, and once the signal has been spotted simply by scanning, fine-tuning is easy from there.
We usually get in the -60's signal with 100mW radios & 31dBi antennas.

There's a nice script on the forums that will make the onboard beeper on RB's beep faster as the signal strength increases - if the RB has been mounted near the antenna, this can make it quite easy for the aligner.

Have you tried the link at a short distance to make sure they link in that scenario?

We tried it only on bench test.

But I just found out something; On the Motorola PtP Link Estimator there is a table to add ground elevations and obstructions on a per distance basis, so I used google earth to take ground elevations measures every half kilometer (pain in the @zz) , add that data to the Motorola PtP Link Estimator and found out this:



So, I believe there is our problem the LoS is just barely above ground obstruction and the Fresnel zone is under ground so this link will not work at all.

In order to make it work I would need to increase the height of Site B to 400' (500' tower),... but then I will start having issues with the Ethernet cable above 300' length (Out of windows collisions) ... I can raise Site A just a little bit because is a self supported 150' tower and after 100' it is almost straight, so the strength of the tower really decreases after 100' and it is already very crowded.



I guess our best bet will be to install site A on another 500' tower we own about 10 miles north, and install a second link between the self supported 150' and the relay point on the 500 footer.
(My boss is not going to like this ) ... anyway I do not see any other way out to make this work.... do you?

I'll keep you guys posted with the results of this "adventure".

Best

Jorge Boardman

I have found the best way to align antennas on a long link is to use a compass. You have the GPS co-ordinates, so can work out the azimuth. An inclinometer will give you the correct downtilt.

We have a high 'first hit' success rate on 40-50km links using these tools, and once the signal has been spotted simply by scanning, fine-tuning is easy from there.
We usually get in the -60's signal with 100mW radios & 31dBi antennas.

There's a nice script on the forums that will make the onboard beeper on RB's beep faster as the signal strength increases - if the RB has been mounted near the antenna, this can make it quite easy for the aligner.

RB532A I believe does not have onboard beeper (maybe I'm wrong, I don't recall it right now) but if that's the case is there a way to add a piezo buzzer to achieve this you are mentioning? Anybody tried that out before?

Best

Jorge

RB532A does have a piezo buzzer...

And you would do well to get into using Radio Mobile as a link planning tool. It's free software, and the SRTM topographical data is also free... Saves the pain of having to plot your own off Google Earth.

Thks for the tips guys, I really appreciate it.

Best

Jorge

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

I noticed that you did a lot of very complex things to try to look at your path, when you could just use Radio Mobile to do it all for you

Have you tried the link at a short distance to make sure they link in that scenario?

We tried it only on bench test.

But I just found out something; On the Motorola PtP Link Estimator there is a table to add ground elevations and obstructions on a per distance basis, so I used google earth to take ground elevations measures every half kilometer (pain in the @zz) , add that data to the Motorola PtP Link Estimator and found out this:



So, I believe there is our problem the LoS is just barely above ground obstruction and the Fresnel zone is under ground so this link will not work at all.

In order to make it work I would need to increase the height of Site B to 400' (500' tower),... but then I will start having issues with the Ethernet cable above 300' length (Out of windows collisions) ... I can raise Site A just a little bit because is a self supported 150' tower and after 100' it is almost straight, so the strength of the tower really decreases after 100' and it is already very crowded.



I guess our best bet will be to install site A on another 500' tower we own about 10 miles north, and install a second link between the self supported 150' and the relay point on the 500 footer.
(My boss is not going to like this ) ... anyway I do not see any other way out to make this work.... do you?

I'll keep you guys posted with the results of this "adventure".

Best

Jorge Boardman

How did you get measured each half km with google earth?
Did You get it manualy or you have a tool for get all values automaticaly?

Tank you,
Matias

Manually.

If you get the newest maggelan GPS maps, and use mapsend lite you can get profiles like that automaticaly.

i've downloaded Radio Mobile to give it a shot for a simple link, and i find it extremely daunting to the point i have no idea what to do
Any guides or easy howtos for wifi?

I noticed that you did a lot of very complex things to try to look at your path, when you could just use Radio Mobile to do it all for you

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

Hi Jorge,

That's not much of a fade margin. I'd invest in some LMR1200 and get the dish up as high as you can. Loss at 5GHz over LMR1200 is quite low - I have a 40M run on a tower where no ODU based radios are allowed due to adverse weather conditions. (heaps of waveguide around - my LMR1200 is the smallest cable up there!) The idea of using CAT6 is also a good one. I'd further go for shielded cable.

Another solution would be to run fibre and DC power up the tower to a NEMA box that would contain your radio unit, a fibre converter, and power for both units. Finding scraps of armored fibre isn't too hard, just ask around.

Cheers,

Jon

It seems he would get more benefit crowding in the top of the left tower with a smaller dish.

It seems he would get more benefit crowding in the top of the left tower with a smaller dish.

Hi, thks for your comment but please explain why.

Best

Jorge Boardman