[RFI] ATT Uverse RFI problem

[Roger W. Macdonald]

Thought you might be interested in my story about my creating some RFI in my neighbors new ATT Uverse cable television system. I think the technical fix may be of some usefulness to other amateur operators and I think it shows what can be done with good cooperation between the ham operator, neighbor, and a company providing the cable service.

About a month ago my neighbor had the new ATT Uverse system installed. Soon it was discovered that I was interfering on 160, 80, and 40 meters. I often run the legal limit and the antenna is a horizontal loop with 750 feet of wire feed with balanced line and tuned with an antenna tuner. The two houses are about 150 feet apart.

First I tried the normal stuff, toroids (type 43)  and/or cable beads (type 31) on the cables to and from the Uverse receivers and modem. These remedies seemed to help out on 80 and 40, but 160 still remained problematic. I then decided to try a common mode choke (type 43) with 10 turns on the service entrance to my neighbors house (see attached pictures). That definitely did the trick for 80 and 40, and at least now I could run about 400 watts on 160.

The other morning ATT came out, changed out all the CAT 5 cable with shielded Cat 5 cable. FYI---ATT will use the shielded CAT5 cable from the service drop to the modem, at no extra charge. They refer to this run of cable as the "Home Run". 

I still I had the problem on 160. So now I am thinking that somehow I am getting into the telephone lines going down the my road. Which I was having a hard time believing as the phone service is underground along my road.

They called in a line tech and he checked the line at the drop from my neighbors pole to his house. There were signs of RF there (lots of FEC errors). They were about ready to just say well there's nothing they can do. At that point I mentioned I had an old overhead drop to my house which is disconnected on my end (I use cable TV and Vonage). The line tech came over to look at my pole and sure enough the old overhead drop was still connected at the pole. He disconnected the old overhead drop at the pole end. His equipment was now showing a decrease in errors by a factor of 100.

So I took off all the chokes on the lines into the modem, and receivers, and the one at the service drop. Now I could run almost a KW on 160. Put the choke back on at the service drop into the neighbors house, and now I could run the legal limit on 160 without a problem.

After the ATT guys left, I went over and paced off the length of my old overhead drop, and guess what, almost a perfect 1/4 wave on 160 ! (about 120 feet, give or take) The old overhead drop was looking like an antenna, and then propagating into the telephone wire bundle (as common mode currents), then coupling with my neighbors twisted pair and and then running into his house. The ATT service guy said that in all probability my twisted pair and the neighbors pair would be physically close in the bundle.

The attached photos show the choke that I put into my neighbors service box. The ATT tech was saying that VDSL signals like solid wire as oppose to stranded wire. I'm not real sure about that claim (his explanation seemed a bit lame), but as I had some solid wire to wind the choke, I decided why tempt fate.  There are 10 bifilar turns #22 wire on the choke.

73 
Roger Macdonald
W8RJ