VSAT Azimuth Elevation Calculator
|Satellite Longitude (orbital slot):|
How to Point a Satellite Dish
After you have installed your dish and have calculated your Elevation and Azimuth angles from the above calculator then you are ready to align your satellite dish. These are the basic steps needed to point any satellite dish (4.8m or an 80cm TV sat dish) as the principles are the same:
- Tip: A Compass or GPS, an Inclinometer and a Sat Finder will make pointing a lot quicker and easier.
1. Elevation Adjustment. Place the inclinometer on the back frame of the dish (taking in to account any dish offset if required – see Fig 5). Adjust the elevation up or down to the desired angle as accurately as possible. Snug the hardware to stop possible movement.
- Tip: Typical satellite antenna offsets are 22.3º and 17.3° (i.e Calulated Elevation – Offset = Measured Elevation angle).
2. Azimuth Adjustment. Rotate the dish to the azimuth bearing (use magnetic North bearing for a compass or True North if using a handheld GPS).
- Tip: If using a GPS, walk out on the bearing a few times and place a marker on the point where the dish should point (Azimuth)
3. Fine Alignment. The satellite dish should now be in rough alignment and will now require to be peaked up on the signal using a sat finder or the satellite modem. The satellite is about 35,000km away so make small adjustments.
- Tip: If using the Sat Finder (see Fig 2 & 3) keep on increasing the attenuation when you are peaking up the signal. This inexpensive bit of kit (about $20) will peak the signal very well.
4. Polarisation. Adjust the LNB skew, the adjustment figure given is from standing behind the antenna. Rotate the LNB in the indicated direction, this is the satellite polarisation angle offset. This is used to preform Cross-Pol isolation tests with the satellite operator and a typical isolation value is 30dB.
- NB: LNB skew is not used with circular polarisation.
5. Secure Antenna. Tighten all the hardware used for adjustment making sure that you do not move the antenna position.
6. Testing. You should now complete an Isolation and compression test with your satellite operator to confirm correct operation and maximum efficiency of the link.
- Tip: Isolation or XPOL is checking if you are transmitting (causing interference) on the oposite pol.
- Tip: Compression test is sometimes refereed to as a 1dB test. A Carrier Wave (CW) is transmitted from the remote to find the point where the Tx signal stops being linear.
I cannot find a Satellite Signal
- Double check your Azimuth and Elevation calculations again;
- Do you have a clear line of sight to the satellite? Make sure there are no buildings, trees, etc. in the way;
- Move away from metal objects if using a compass;
- Is your dish offset (like the picture above)? Double check your offset value;
- Set your Elevation and move the dish through 180° in Azimuth;
- Check your LNB (see below);
- Remember your compass is correct – you are wrong!
I have found a satellite signal but my Rx is not green/locked
- The sat finder only detects RF energy and not whether you are pointing at the correct satellite or not. Don’t worry you will not be too far away;
- Measure your Azimuth and Elevation again;
- Read the wiki about the Clarke Belt. Depending on where the satellite is in the Clarke Belt you will need to go right or left and up and down;
- You could always mark the starting position or count the number of turns you make so you can always go back to your starting position;
- If you are using a SCPC sat link then check things like the MODCOD, bitrates, FEC, etc with the distant end.
I think my LNB is not working
Here is a quick and easy method to tell if you have a knackered LNB (Rx – Receiver) or not.
- Point the dish to clear sky within your reach;
- Put your hand in front of the Feed Horn assembly (due to RF energy make sure there is NO Tx signal at this point) and you should see the noise floor increase and decrease on a spectrum analyser or your sat finder box as you move your hand in front of the feed horn;
- Your LNB is working OK;
- Keep on aligning the dish.
How to find your satellite fast! if you want more top tips!