how to make antenna for 2100MHz?
this is for idea net setter?
how to make antenna?

You dont' need to make antenna, if you have signal problem then why don't you buy an USB extension cable and then place dongle to some higher place. I have done this several time

Also, if you are really facing signal issue then why don't you buy a 3G router which comes with antenna and all that, you can place it any convenient position in your house and then connect laptop or computer to it through WIFI.