Topband: A Tale of a Successful 160 meter RFI Hunt

[donovanf at starpower.net]

A few weeks ago I noticed a new source of intense broadband RFI 
had appeared on 160 meters and adjacent frequencies from 
approximately 1500-2000 kHz. There is no trace of RFI on any 
other frequencies or from any direction other than approximately 
325 degrees azimuth. 



This RFI is unusual, it appears to be nearly white noise with no 
apparent spectral shape. I t sounds like white noise when received 
with an SSB or AM detector, there is no trace of a 60 Hz component 
or 60 Hz harmonics like AC power line noise and no spectral shape 
like switching power supplies. 


Using my 350 foot diameter 8 element 160 meter electrically 
steerable 160 meter receiving array (thanks W8JI and W5ZN) 
I determined that the RFI is arriving at my QTH at an azimuth 
of approximately 325 degrees. 


Using a Tecsun PL-660 handheld receiver, W3UR and I fairly 
quickly determined that RFI source is a Travelers Information 
Service transmitter near Interstate-70 on 1700 kHz about two 
miles distant and at an azimuth of 318 degrees from my QTH. 
The TIS transmitter has been operating for years with no trace 
of RFI but obviously something has now gone badly wrong. 
It uses a fifty foot vertical tuned to 1700 kHz. 


The next step is to get the failed TIS transmitter turned off! 
That's my task for tomorrow. 


73 
Frank 
W3LPL