Sparklies on analog can occur for several reasons:
Antenna misalignment - azimuth, elevation and declination correct?
LNB / Feedhorn misalignment - is the f/d correct? Feedhorn centered?
Probe polarity misadjustment - adjust skew
LNB frequency drifting or is the TP frequency assigned to be offset fron the standard mapped frequency?- adjust lnb frequency LO (offset) White sparkies = frequency is high, Black = frequency is low.
Incorrect bandwidth selection- Is the transponder using full TP (36MHz) or less?
RF interference - Usually affects certain TPs when the dish is turned in a certain direction. Use filter to attenuate specific interferring frequency or shield the dish.
Moisture can get into the feedhorn, LNB.
Water can wick into the coax and severely attenuate signals.