A method for monitoring radio frequency interference (RFI) in a pass band of a satellite signal is provided. The satellite signal includes a carrier signal tracked by a carrier tracking loop located at a receiver. The method involves calculating a statistical variance estimate based on a plurality of discriminator values formed in the carrier tracking loop and calculating an RFI detector from the statistical variance estimate. The method is particularly useful for detecting continuous wave (CW) and narrowband RF interfering signals in the tracking loop pass band.