I had a similar signal on different bands and found it to be my "smart" battery charger in the garage, and the other was the charger for the 12V back-up sump pump battery back-up system in the room next to me. I put a timer on both of them. I'm a happy DXer now!!
My new tool to find the noise is a Kenwood TH-F6 handy talky it has a general coverage receiver with and internal antenna for SW and has a signal meter. Once you find the frequency with the Flex tune the Kenwood in and go around the house when it get full signal on the meter turn off the internal SW antenna and use the rubber duck until the signal is full again then remove the rubber duck and by the time it's full again you should be very close to the source... Good luck on your hunting. (any portable SW receiver will assist in your Fox hunt)
Dan -- KC4GO
I think I have found my noise source - it's the computer that runs SSDR! I used another radio (K3 with P3 pan adapter) and saw the same repeating signal on it. When I turned off the SSDR computer, the noise went away.
Likely cause is the switching power supply in the computer. Replace it with a high quality one from Corsair which are pretty quiet. Try putting torroids on all leads into and out of the computer. Make sure the computer case is a Farraday Cage. ...remove paint around the case screws so they make contact.