Topband: High Efficiency Furnace RFI?

donovanf at donovanf at
Sat Jan 15 08:43:37 PST 2011

In the last few weeks a new strong variable frequency 100% duty cycle RFI source suddenly appeared on 160 meters, radiated from a home one mile southeast of my QTH 24 hours per day.  The RFI peaks in the 160 meter band on variable frequencies mainly between 1801 and 1834 kHz.  Yes, its the perfect RFI storm on 160 meters!

Its source is a home with a recently completed major addition.  At my QTH the RFI affects only 160 meters and the AM broadcast band above 1600 kHz. If you place an AM receiver close to the home generating the RFI, the RFI extends only from 1270 kHz to 1970 kHz.

The RFI has amplitude peaks and valleys at 1801, 1804, 1818, 1823, 1827 and 1834 kHz; however, all of those RFI peaks are not present at the same time. The RFI abruptly switches among those frequencies a few times per minute, apparently caused by some sort of variable speed controller.  If you listen to the RFI with the receiver in the AM mode, the RFI has a continuous AM modulation of approximately 1 Hertz.

All of the above -- especially the one mile distance from my QTH -- suggests that the source may be a new high efficiency heat pump with a variable speed motor controller.  

While I can probably use my DX Engineering NCC-1 noise cancelling controller to completely null out this RFI source in every direction except SE, I would prefer to eliminate the RFI source entirely!   

Has anyone else experienced this type of RFI?  If so, have you been successful in resolving it?



More information about the Topband mailing list