Mean level interferences ( <40db above quiet sun)
At the lower end of the band (< 300 MHz):
It is very difficult to find a 1 Mhz clean band
Interferences have a small bandwidth ( 5-20 kHz)
This imply:
Small observing bandwidth, very good filters.
Digital interference excision will
require high dynamic, high resolution spectra and filters.
There are (at present) less problems above 300 MHz
Don t forget internal interferences, mainly from high speed digital electronics.