Special Issues at Low frequencies: Interferences (ctd.)
		• Low frequencies  ( < 2 GHz) are crowded: – Very powerful transmitters (TV and FM) (emitters ~100 kW) – Low power transmissions and GSM (emitters of 10 - 100 W) – Satellites – Protected (for radioastronomy) bands are very few and difficult to keep free of interferences: – 151, 327, 408, 610, 1400 MHz… with bandwidth from 3 to a few ten MHz, in principle . – Satellites emissions may occur very close (149.9 MHz) to astronomy band – Antennas provide usually a poor rejection ( 10 db)