Alignment of Antennas

[Anuj]

Hi
I am facing a lot of problem in antenna alignment specially when i have large diameter antennas (2.4 or 3m dia). We use a multimeter and binoculars for alignment. Is there any instrument available which can be used for alingning and setting of azimuth and vertical angles?
Thanks

[roger]

Dear Anuj,

there's several ways to align antennas,anyway a big diameter antenna is hard to align,you must use the azimuth and vertical angle given by pathloss and your binoculars,then multimeter doesn't give you a stable RX level,so if you're using PDH equipment you'll use NECTAS software,in SDH case use 1320CT,it's a monitoring software,it'll give you the RX level in DBm, I presume you know how to use it.


Roger

[Paul]

Anju,

Andrew Antenna publish an excellent document that describes how to align antenna correctly, its called Alignment fundamentals for Parabolic Antenna reference SP20-35. The first thing is to make ceratin that the antenna is perfectly horizontal if the vertical angle is anything less than 1 deg. You can do this by placing a spirit level on flat part of the antenna such as the launch unit of the top of the radome. On a 40km path with an antenna with a 1deg beamwidth you will have a final beamwidth of 700m at the far end, so you can see that if you are 2deg off Horizontal you could miss the far end tower by 800m. The rest of the process is down to patience.

good luck

[Anuj]

Hi
I ckecked with Andrew for the document that you have mentioned- they say there is no document with that ref no. Can you give more details from where can i get that info.
Thanks

Anuj

[Vic Rhys-Williams]

Anju;

Forward your email address to the above and I will email the Alignment Fundamentals for MW antennas to you.

Cheers,

Vic R-W

[acherman]

I'm not sure if this will help, but it will give you an idea. I used to work on a tower crew with Telus Communcations Inc. When aligning microwave dishes there is always the problem of that 1 degree beamwidth spreading out at the far end. We always did our alignments at night. It's a little interesting but it works. What we did is strap a high powered lantern (flashlight) to the top the dish (we always had Andrew high perfs with the shroud on them) at both ends and used the light to do the alignment. Of course, you have to make sure your light is dead center on your dish and exactly parallel, but you just have to align the dish to max intensity of the light. After that just fine tune with a DVM.

I hope this gives you some ideas.

Aaron

[ANUJ]

What we do here is by the following steps:
1. Determine the site location by using mirror reflection and powerful binoculars (applicable for 0 ~ 60Km hop distance)
2. Direct the antenna of site A to site B's mirror reflection.
3. Turn on radio on both sites.
4. Measure RSL by AGC voltage or power meter.
5. Move antenna at site B left to right to obtain maximum RSL at site B.
6. After moving and fixing antenna (@ maximum RSL)at site B repeat steps above for site A to obtain maximum RSL.
7. For fine tuning, you can use the elevation angle adjustment of the antenna to up tilt or down tilt the antenna for maximum RSL on both sites.

NOTE: Mirror testing is essential in determining if there is line of sight. Make sure polarization is the same.

[JAD]

What we do here is by the following steps:
1. Determine the site location by using mirror reflection and powerful binoculars (applicable for 0 ~ 60Km hop distance)
2. Direct the antenna of site A to site B's mirror reflection.
3. Turn on radio on both sites.
4. Measure RSL by AGC voltage or power meter.
5. Move antenna at site B left to right to obtain maximum RSL at site B.
6. After moving and fixing antenna (@ maximum RSL)at site B repeat steps above for site A to obtain maximum RSL.
7. For fine tuning, you can use the elevation angle adjustment of the antenna to up tilt or down tilt the antenna for maximum RSL on both sites.

NOTE: Mirror testing is essential in determining if there is line of sight. Make sure polarization is the same.

OOOPPPSSS sorry wrong name.
JAD

[Sergio Pini]

The topic is the frequency of the Link, you should define the azimuth of the stations first (with GPS) it always begins with the horizontal of the antenna, later with the vertical.
If the Radio ei equiped with ATPC it should be extracted or to pass to manual, to maintain fixed the power of the trasmiter.
You should guide yourself for the tension of AGC and to confirm with a Bolometer, the mensuration of Alarms & status, of the application has an error of + / - 3 dB. it is alone of reference and it is not good for the adjustment.

Good luck.

[Hossam_El_Meadawy]

For long path and big diameter antennas; there is one think that you have to watch out for.
You should take very good care of the narrow beemwidth of the big antennas.
and the multipath activities that can take place in the long path.
Thus the center of the beem can shift a little bit.
the alinment has to be done in mid day, and redone 2 more times in 2 different days to make sure you did the optimum alinment.