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Major World-Wide RFI Sources   update 2011/11/20





Interference Range

1. Woodpecker



~10Hz OHR

7-19 MHz

2. Sweeper I



~100 kHz/sec

5-26 MHz

3. Sweeper II



~125 kHz/sec

5-22 MHz

·  1. Woodpecker: A high power, low PRF radar signal consuming a bandwidth of 40 kHz or so changing frequencies every several seconds. It operated over the range of 7-19 MHz.

·  2. Sweeper I: A high power, sweeping carrier (about +100kHz/sec) starting from around 5 to 7 MHz and sweeping up to 15 to 26 MHz at times.

·  3. Sweeper II: A high power, sweeping carrier (about +125kHz/sec) starting from around 5 MHz and sweeping up to 22+ MHz at times. There appears to be more than one transmitter and they may be out of phase or on a different sweep range. Operation may be 24 hours but reception times and frequencies here on the west coast of Canada seem to correspond with a transmitter in East Asia, perhaps China. In November it has been heard to some extent almost around the clock but not so well form 1800 to 2200 UTC (bad for Asia to Western Canada).

If you monitor a fixed frequency say 7 MHz, the main signal passes by about every three minutes. It is easier to detect with wide receiver IF bandwidth and in SSB or CW position.

Another possibly related signal can be heard sometimes in the 11.9 to 12.3 MHz range sweeping at about 2 sweeps per second and only over 100 to 200 kHz with an AM buzz.

·  4. Sweepers: They are still easliy audible here on the west coast but amateur operating activity is quite low these days so I guess this section will be gone soon (along with amateur radio?).

Any reports or ideas on Sweeper II?   Please contact me with any information at: