[Elecraft] Notch filter question

[Randy Cook]

I am the owner of K3 #2050, and still learning its use.  I haven't  
been on the air much in the past half year, but did work the bands for  
a day in the last ARRL SSB contest. It was a good chance for me to  
better understand the noise reduction and filter features.  In using  
the Notch filter (NTCH), 'auto' worked fine, except when the offending  
signal was below about 1500Hz.  In order to remove whatever the signal  
was below that threshold, I had to go to 'manual' mode.  I could find  
nothing about this in the documentation.  Is there some frequency  
limit for the NTCH Auto function? Another K3 user thought it could be  
related to the SSB bandwidth.  Any ideas?

Randy- K6CRC
k6crc at arrl.net