Two weeks ago, on a Friday, I noticed interference on 4m. It took the form of groups of four carriers, about 50hz apart. The groups were spaced at about 40kHz intervals all across the band. The max strength was about S7, though not all four carriers were equal in strength. There was one right on the WSPR weak signal frequency. I use a Flex 1500 which is given to images, so although the groups of carriers were to either side of 70.200, an image was right on it. On FM there was a group of carriers on just about every channel. In addition to this there was hash everywhere. Although most HF bands were less affected by the carriers, the high noise level was everywhere. 2m was not affected.
This discovery came during antenna work here, so I spent some time fruitlessly examining what I had done. Eventually I noticed that I could get a beam heading on it, suggesting that it was nothing to do with my site, and I realised that the FM evidence meant that an entirely separate system with its own antenna was equally affected.
On Saturday I went out with my Wouxun and toured the area. A new solar panel installation was suspect, but it is noiseless as far as I can see. Eventually I found a great deal of noise coming from our pond pump. This was odd as the pump is at 90 degrees to the peak beam heading. After a great deal of disconnecting and tinkering at the pump it suddenly dawned on me that I could get the noise on the rig anywhere near our mains wires. the pump had simply been one source of the noise. It was everywhere in the house - my house.
Trying to notch the interference out using notch filters was pointless, as every so often the interference would change gear and move several kHz in either direction.
After more pondering, I recalled that a van had been parked next door on the Friday. I recognised the van as that used by the local antenna engineer, who doubles as general installer of technology round here. A quick enquiry revealed that a BT Vision system had been installed next door on the Friday morning. The house next door is fairly new, and open plan inside. I was surprised to find a Power Line Adapter (PLA) link had been used to connect the pre-existing BT router to the Vision box. Surprised, as BT say that if the router and the box are in the same room then they will be wired together. Although the two were about 4 metres apart, the only sensible wired route was via three walls and over two doors, an overall length of about 7 metres. Being a charitable soul, I supposed that was why the PLAs had been fitted, though I now think that this is done as a routine, however small the distances.
Needless to say, putting the Wouxun near the PLAs produced a howl of protest, and turning them off made the noise disappear. It was not so much that this interference was at its worst beside the PLAs, it was that the mess was appearing in my house wiring. My neighbour was very co-operative. She agreed to take it up with BT. In the meantime I just had to put up with it and try to think of what to do next. I thought that wiring the neighbour's house would be the best route, but she was not keen on that idea.
After an initial contact with BT, there was a long phone conversation with their help line. The BT guy had to endure alternating blasts from the neighbour and me. He was keen to deny any responsibility in all this. He also got confused as he tried to bring us back to the idea that this was a wi-fi problem. My neighbour eventually put a stop to that excuse by pointing out that her BT router had been there before the Vision installation. The guy tried to claim that he could not help with anything other than getting the BT gear to work and that anything else was "our problem". The neighbour put it very well "before the installation there was no problem, since the installation there is a problem, so you cannot keep saying that BT are not involved in fixing it". We were put on hold several times.
Eventually we were put through to a supervisor. He seemed to understand the problem but he was still pedalling the same line. He told me that "all electrical devices produce electro-magnetic interference", which was something to talk about, but maybe some other day. My neighbour kept battering him verbally. Eventually he said that the only way to solve the problem was to put a wired connection in - at my neighbour's expense. She was not keen on this but he said that BT would provide telephone support over to phone to explain how to install the cables ("clip it up, plug it in" I guess). He also persuaded us to try a replacement set of PLAs, which would be sent to my neighbour by post.
I left this as it was, but we all felt that wiring the house was the only real solution. Although the neighbour thought that I should not pay, I was prepared to buy the Ethernet cables and sockets she would need. I wanted to be sure that well screened leads were used.
The next day my neighbour phoned me to say "it is fixed". I was a bit doubtful about this, so I went round to see. She had moved the router to beside the TV and plugged it into the (main) BT socket which was located there. It turned out that, 3 years before when the house was being built, she had used the same guy who installed the Vision system to advise her then. He had advised her to get her main BT socket beside the TV "as internet TV is coming". To move the router she had to change the position of her internet phone, which had been connected to the router. She was happy enough to change all this around.
I had never realised that there was a BT socket beside her TV (actually, inside a cabinet). However, the installer who put the Vision box into the house must have been aware of it at some time, as it was his idea. It was him who told her to put it there, and it was also him who wired the extension socket which he later connected her router to. So despite the instructions from BT to connect it the router to the main socket, he had put it on an extension, and he had forgotten where he had specified the main socket to be.
So, the house is now wired - with BT phone cables.
That was a narrow escape. I only had to endure it from Friday until the following Wednesday. The only remaining effect seems to be hash from the TV or maybe poorly screened Ethernet cables on the new installation.
What I seem to have learned is:-
1) the installer will use PLAs whatever the layout of the house
2) BT help services find it hard to understand what you are talking about
3) wiring the house is indeed the only answer
4) check to see if a wired solution is available.
5) whatever the claims to have notched amateur bands out of the PLA range, 4m seemed to be worst affected
6) try to stay on good terms with your neighbours.
Do not have PLAs anywhere near you.