[RFI] Pulse noise on 40

[K8RI (Roger)]

The past couple of nights at various times between 10:00PM and 4:00 AM 
I've heard a pulse noise that sounds like an electric fence *except* it 
is more or less a discrete frequency about 3  to 6 Khz wide.  It was 
slowly drifting upwards at a rate just fast enough to hear the pitch 
change. OTOH it didn't take much over 10-15 seconds for it to move clear 
through the receiver bandpass. This was a pulse with a repetition rate 
of about 1 Hz on and 1 Hz off.  It would come and go abruptly. It might 
only be present for a few seconds or a couple of minutes.  Signal 
strength varied from down in the noise to a max of about S5. There were 
extended times (half hour or more) where I didn't hear it at all.

It did not appear to be stable enough to be a regular transmission and 
unlike most timed noise sources such as electric blankets, heating pads, 
and electric fences it was a discrete signal and not just broadband 
noise.  It really didn't sound like any over the horizon RADAR I've 
heard before. I heard it mainly  between 7.170 and 7.190, but I think it 
was present over most of the band at one time or another.  On several 
occasions it sounded like it was turned off in the middle of a pulse.

Any thoughts?

73

Roger (K8RI)