[TowerTalk] Yet another radio interference!

[Luciano Nachif]

I installed a 40 meters Cushcraft 40-2CD 2 elem. yagi on a 125 foot tower by May 2nd.
On first few days it sounded like a dream. Noise was around S3 and no interference whatsoever.
 
Some days after installation, I noticed that I could hear a 3KHz bandwidth noise every 24 KHz on the entire HF band, night or day time (24 hours a day). Strongest noise was around 6,8 to 7,1 MHz despite antenna or radio. ( I also performed some tests with a Sony portable radio ICF-7600GR set for LSB)
 
On the next weekend, when I came back home, the interference was gone. For 18 days in a row no intereference showed up. Everything was pretty good.
 
Ten days ago, it came back and it is a S-7 to S-9 depending where the antenna points to.
 
I decided to go for a walk around the block and noticed that the noise is either on the power lines and/or cable telephones. It starts 100 feet before and 200 feet after my house main gate.
 
When scannning from 1MHz to 30MHz, it peaks around 6,8 to 7 MHz.
 
If there's anyone on this list that can help me, please, do so!
 
I appreciate your help!
 
Best regards,
 
Luciano PT9KK