Do-It-Yourself/Satellite dish installation
This article contains information concerning the installation and calibration of satellite dishes.
Signal comes from the satellite & reflects on the reflector of the satellite. Then it goes to the sub-reflector & the concentrated signal from the sub-reflector goes through the feed horn. The signal from there goes to the ODU through RF Cable (RF signal goes through RF cable). Usually Wave Guide or Coaxial cable (of 50 ohms) is used here. The length of this cable is also very short (usually not more than 1 meter). The ODU manufacturer usually sets the type & length of the cable.
After the antenna, ODU comes in place. What type ODU will be used is depending on the Modem manufacturer. According to the Modem’s Tx & Rx signal we need to select ODU that fits it’s requirement. Tx & Rx from ODU connects with Modem.
The signal from ODU goes to the Modem through IF Cable (IF signal goes through IF cable). Usually Coaxial cable (of 75 ohms) is used here. IF cable can carry signal up to 100 meters, after that we need to increase the strength by using a repeater. We can use longer IF cable than RF cable because Radio Frequency >> Intermediate Frequency. This is why; we setup ODU outside & use shorter cable.
Alignment of the Antenna with the Satellite for modem use
To do this first we need to know the co-ordinate of the place where we are going to setup the VSAT antenna. We can know the Altitude & Latitude with GPS. Now we need to decide which satellite we are going to use. After knowing the co-ordinates we need to go to the website of the satellite & put the co-ordinates over there. Then it will show the angle & the elevation of the antenna that we need to find the satellite.
Now we need to go to the site and observe very carefully that the place where we are going to set the satellite has any obstacle or not. If it has an obstacle then we need to slightly adjust the place of the antenna. After checking every thing, we need to setup every thing in above-mentioned way. Then we need to align the Antenna with the satellite with the angle & the elevation we get form the website of the satellite.
After aligning the antenna with the satellite now we will tune it farther. To do this we will connect the Tx of ODU with a spectral analyzer. Then we will see all the frequencies that are working in the satellite. The satellite service provider will give us a frequency. We need to set the frequency at the center of spectral analyzer. Then they will send a pure carrier signal from the satellite. This plain carrier is known as Beacon Signal (the signal which is not modulated). The pick of this signal will be slightly shifted form the center, either right or left. Then we need to rotate the feed horn of the antenna very slowly to bring the pick of the signal at center of the spectral analyzer. This means that the antenna have been aligned properly.
Now we reconnect the modem & configure it wit the same Tx & Rx frequency. Then we send a signal & if we receive it then it means our receiver & transmitter is working properly. Then we change our receive frequency at the given frequency by the satellite service provider. Then we send a signal & the satellite service provider will re-check it with a spectral analyzer. This process is known as Cross Pole. If they find the signal in the right place of the spectral analyzer it confirms that the link has been established properly.
Personal Satellite dish
The theory for your satellite dish is similar. But a spectrum analyser or a power meter are not a necessity. Such equipments can be expensive.
1)First you need to know the position of the orbiting satellite what you want to target. eg. Hot Bird 13º west.
2)Then you need to know your coordinates on the globe latitude and longitude. For example in Cyprus, Nicosia 34 degree of latitude and 34 degree of longitude (approximative) .
3)Using these data , You can calculate (see link below) the angle of elevation of the dish, and its azimuth angle or degree of movement, left or right. Results for the example: an azimuth angle of 214 degree and an elevation of 44 degree .
4) Then as these measurement are all more or less accurate you need to tune around the position in order to get maximum power, or in case of a TV program , a good picture. Note that a lot of Set top box (STB) have a power meter function, it is just a display of the power on the TV set, which will help to obtain a good tuning .
Note: your Low-noise block converter (LNB) place on the antenna, needs to received 12 to 15 V of DC supply through the coax cable, otherwise no power can be transmitted.