Why uplink frequency is greater than downlink frequency?

Hi Vasudeo. I'm assuming you mean uplink and downlink speed. With home internet service providers your download is usually much much faster than upload and you can see that by running some simple tests at sites like Speakeasy or testmy.net (my favorite) that can test up and down at the same time.

It's best to have fast download because most of the time you're downloading things (web page, video, sounds, files, email, etc) but you're rarely uploading except if you're posting pics to Facebook, sending email, etc.

If you do notice, however, that your upload is faster it's likely that you're already downloading something (a file or in iTunes or something) when you're testing your speed. Or you're using a shared internet connection and someone else is downloading something. Try again a little later and you'll probably see that download is indeed faster. Does that help? I hope that's not too much info.

1) On the Earth Station we have to penetrate the atmosphere to reach the satellite station.. so we need a lot of power to be generated... This is only possible with the help of High power transmitter circuits... which cannot be installed on the satellite... so uplink is at higher freq with higher power.

2)Now as the frequency is increased the amount of interference caused by the atmosphore reduces... as higher frequency signal has more signal energy in it... so it can penetrate the atmosphere more easily... (the same reason why we use modulation with higher frequency)

3) Unwanted distortion like rain (main cause of attenuation), fog, other frequency in neighbourhood, etc cause distortion... so we have to count to these factors and increase the frequency band to 100-1000Ghz range...

Now the Satellite is a small piece of equipment and needs to be light weight... so it cannot have high power amplifiers on board so by default the freq is lower than uplink...

Jaywant007 from edaboard.com by Naser Salah