Image By NASA(who else could take it?)

Image By NASA(who else could take it?)

I had been visiting a lot of hill stations since i was a kid. I even lived in Nainital for a few years when i was little. Television was never so common at all those places until the DTH services gained popularity in India. I recently made a visit to Arunachal Pradesh and saw a DTH signal receiver at every house. I wondered how it worked so effectively at all those places, and why our cable TV did not.

TV technology could be analog or digital. The usual cable broadcast TV use land-based antennas that transmit a radio signal(using the Vestigial Sideband Technique) . Now, to avoid interferences and provide HD picture and sound quality, the receiver antenna must be in the line of sight of the transmitter.  However, the shape of our planet does not provide for it.

But, this line of sight could be increased significantly if we were to send the signals from somewhere high above-from the satellite. Now, the signal from the satellite reaches directly without any obstacles-and, to a larger number of customers. There is just one problem if you may think-the satellite is in its orbit, so do we keep aligning our antennas to its direction?

Well, that is taken care of by using geostationary satellites. By “geostationary”, we mean satellites that are stationary with respect to the earth(geo-stationary). And by the way, these satellites orbit in space in a region we humans call The Clark Belt or The Clark Orbit.

geostationary orbit

geostationary orbit

Now, there is another additional advantage of using Satellite TV. We can use a DVR(Digital Video Recorder) to record live TV shows with our satellite TV. This is easy as the signal is already a digital signal. While in analog TV(cable TV) we must first convert the signal to digital if we want to record it for later viewing.