Both gripes from users and continued spectrum monitoring initiate in-house and off-site searches for the source of Radio Frequency Interference.
The digital equipment used in various backends, frequency synthesizers at different mixing stages of the IF/LO, electric motors, video cameras used for safety-status monitoring, on-site vehicles, displays at the Visitor Center could in principle cause internally generated RFI.
These two memos describe recent investigations of internal RFI:
For detecting RFI generated off-site, a Mobile RFI-Detection Unit, is indispensable. Towards this, NAIC has recently acquired a van. This now partially equiped.
More to come (and picture - to be linked).