Topband: Broadcast Interference

[wa4fki]

I would like help, recently BC interference has become very bad. A few days ago 160 and 80 meters are almost useless due to two radio stations beating together. 

Upon investigating I found that one station (1600 kHz) was one of the problems, it's signal was beating with a station on 640 kHz. 

The 640 kHz station has a 3rd harmonic in 160 meters, distance from this station about 8 miles. While the 1600 kHz has a sub harmonic on 687 kHz. 

I receive with a Kenwood TS-140 and a Drake R-4B, the problem is very bad on both. Recently the Drake 2-B is even worse than the TS-140. By inserting the 20 db attenuator in the TS-140 the 9+40 on 70 meters drops to S-1. Any suggestions? 

Bill
WA4FKI