Wednesday, 20 June 2018

Power Line Adapter noise interference solution?

I have been writing these posts as multi-subject essays but I hope from now on to do just one thing at a time and just make more posts (!).

About 3 weeks ago our neighbour installed power line adapters. The PLAs in question were branded TP-Link but there are lots of makes. Some make less noise than others.

How did I know that my neighbour had installed these? Well, the 50MHz band was immediately submerged under a wall of radio noise. Much tinkering with the Noise Blanker settings on the Icom IC-7300 allowed me to separate out two distinct types of noise - 1st a sound like a chicken clucking which was there 24 hours per day and - 2nd a wideband swoosh of white noise of varying strength which happened at certain times. Presumably a constant status signal with wideband saw-tooth type signal when data was being exchanged.
Sudden peaks in the wideband noise and regular "clucking" all the time.

At this point I am going to try to upload a video clip to this blog. If it works it shows an unsteady image of the IC-7300 receiving the noise, and at one point me turning the noise blanker on to reveal the two separate components. As I have never managed to upload video successfully to this blog platform we shall see if I can get it to work.

Although the noise blanker could be made fairly effective against both noises this required me to adjust it to maximum settings. When I did that reception of FT8 was affected. So with NB on I could combat the noise to a large extent, but then I could not use the radio. Turning the noise blanker off pushed the AGC into overdrive and signals vanished.

This is always a difficult situation as my neighbour was simply following the advice of our local television antenna/satellite dish installer. This particular installer loves installing Power Line Adapters (PLAs). The idea of the PLA is that it works by injecting an RF signal down the house mains supply wires and then receives the signal somewhere else. The units are fitted with Ethernet sockets, and in this case were connected to an internet router at one end and a television at the other end. They are cheap, and easier than cabling the house. So he uses them a lot.

I needed to be pretty certain that the noise was coming from this source. It is not easy to approach a neighbour and suggest that something they have just bought is causing me problems when it is clearly not causing them problems. Especially if you have picked the wrong house to blame. So, amongst other things, I swung my beam round to see if the noise was directional (if it isn't it is probably coming from this house). The neighbour's house is located South West of me so I took compass bearings as I turned the beam.

This is not the first time this has happened to me. Last year my neighbour on the other (East) side had a similar experience. She had installed a proprietary internet TV system supplied by BT, and the same installer fed it using a pair of BT branded PLA adapters. The resulting noise then was FAR worse than this time, as it was clearly getting into the mains supply of this house. That problem was resolved by the neighbour accepting my offer of a wi-fi alternative to the PLAs.

So I offered the same solution to the second neighbour with the latest PLA installation. He told me that the installer had tested the wifi signal and that no reliable wifi could be found at the television end so the installer had sold him the PLAs. I offered to try out a wifi solution at no cost to him. He agreed to this and I followed the same process as before. The device I tried was the same as before and still listed on Amazon as:-

DC XINGDONGCHI Wireless-N 300Mbps WiFi Range Extender Router/Repeater/AP/Wps Mini Dual External Antennas Wifi Booster Wireless Access Point with RJ45 Port (Wi-Fi Booster)

Hyped up to sound like a pretty amazing product, eh? You can find it here for £14.99:-

EDIT:- In the past couple of years it has gone up to nearly £25. I cannot keep up with the price but it was still available last time I checked. The first system has now been in use without fault for 4 years.

Whatever else it can claim to do (it is basically a wi-fi repeater), it has two key features for me. First it has two Ethernet sockets and can provide an Ethernet output for wi-fi links. And secondly, it has a very sensitive wifi receiver. It doesn't photograph very well:-
The wifi to Ethernet hub as bought from Amazon (inverted photo)
Anyway, over the past year I have bought 4 of them to solve various similar problems. The neighbours on both sides now have them to replace noisy PLA systems, and in both cases the noise level has fallen back to negligible. I also have one myself which gives a perfect picture on our television, whereas the on-board wifi cannot find a satisfactory signal. I fit them with CAT6 cables to reduce RF interference (both in and out!) and set them up for repeater mode on the domestic wifi. Then I just connect the Ethernet cable to the television.

There are two Ethernet sockets, so a fourth one has been used by me to provide a wifi fed local area wired network for two computers. This is not completely noise free but pretty good - certainly miles better than PLAs could produce.

I had expected to have to fit a repeater to reach the television in the case of the second neighbour. After all, the TV installer had said that the weak wifi signal required him to sell them a set of PLAs. As it turned out the XINGDONGCHI device got a perfectly good signal from the domestic router located at the other end of the (large) house.

No doubt other products are available which do the same job, but these ones suit me. They are cheap and effective. Some reviews say they are unreliable in the long term, but the first system has now been operational for a year.
Hub turned on and sending data to GM4FVM's LG television via the cable
Perhaps the main drawback is the bright blinking LED light display. Homer Simpson from the popular television cartoon series "The Simpsons" has a solution for this type of thing. He sticks some black tape over his annoying car "low oil level" warning light  Perhaps for this in a domestic setting we might use neat white insulating tape. Note that with UK plugs the device appears upside down. The upper photo has been reversed by me, the lower one shows the device as it actually appears - upside down.

Anyway, in my view PLAs are terrible. They are supposed to be "notched" so as not to produce signals on amateur bands, but the TP Link ones produced nasty noises on the 50MHz bands - but not on 28, 70 or 144MHz. Anyway, the best solution seemed to me to remove them entirely.

We will need to see in the long term how effective these are. Mind you, for a year now the first one is providing a reliable signal to a BT box. That device happily streams high definition video (so does mine for our TV). Bandwidth does not seem to be a problem. The resulting data speed has so far proved just fine for my neighbours and me.

All this makes me think of a different issue. BT supply their steaming box (which is a hybrid "Freeview" digital TV recorder and internet decoder) with only an Ethernet socket for connectivity. At the same time they advertise their Broadband internet service as having the best router and wifi signal available. Do they not trust their wifi signal to supply their television box? So far I find that my neighbours are perfectly happy to have wifi connections instead.

And I am perfectly happy to stop all that noise.

This is bad business for BT. I decided not to buy their box as unless it was right beside a router it could only be supplied with PLAs. Now I discover that was never true. In these three installations PLAs are not necessary for domestic television viewing.

Final thought - you might have PLAs in your own house. It might be worth doing away with them and I am sure you can come up with a solution - maybe hard wiring using at least CAT6 cable?

Power Line Adapters? I say "Down with this type of thing".




  1. Here here Jim! Ban PLTs, they are an abomination. Putting RF down mains wiring is crazy, much as is trying to put broadband down Victorian copper telephone wires, rather than going optical fibre as we should have done. You much have the gift of the gab to get your neighbours to agree to tackling this. I had a devil of a job just to get my neighbour to try a ferrite on the router next door!

  2. Hi Jim,
    Seconded. It's not the technical problem but the social problem that is the difficulty in sorting the neighbour(s) out. I came home from holiday at the end of August to find one of these had been installed somewhere nearby. Although today, for the 1st time it seems to have gone. Maybe the owner was experiencing problems and found out PLT's aren't a good thing. If it re-surfaces your solution is good news. 73 Bob G8HGN JO01fo

  3. Hi Jim, Thanks for an interesting article. I just took my foundation exam today and was thinking it might be a waste of time given the huge interference levels I have been experiencing. I assumed it was the railway I live right next to but after some troubleshooting today I discovered it was the 4 PLA’s I use, all TP link, which led me to your article. Time to remove them and hard wire!

    1. dont go with wires, use wifi dongles and if the range isnt good enough, get a repater like above. With cables and routers you are creating another ground loop :)

  4. This comment has been removed by a blog administrator.

  5. Thanks for this post. I have uploaded a video think it was exclusively mains hum, but I think alot more of it is the TP-Link adaptors. Will unplug now and find out !
    Kind Regards/73's Alan/M7ALU

    1. - after removal

  6. Hi Alan.
    Suddenly there is a lot of interest in this older post.
    I do not usually tolerate people posting video links but yours is exempt. That is serious noise. I watched both videos.
    It can be worth turning things off at the mains breakers to trace what is happening.
    Strange things can cause nosies like this. I had a cooker hood which I found had a switch mode power supply under the covers. I only traced the noise by turing off at the breakers one at a time. Surrounded it in Bacofoil (the PSU inside not the whole cooker hood...). Also anything with a power supply. Things like car battery chargers, phone chargers can be bad. In this house they are all off when not in use.
    This is particularly a thought for you - digital model railway layouts can be terrible. The units pass the requirements, but once you connect them to many metres of track they can be awful.
    Keep trying, lots of those noises can be traced and dealt with.
    73 Jim GM4FVM

    1. Many thanks for getting back to me (and allowing the videos). Indeed I used a circuit breaker method. Found the errant noise maker is an electric blanket - my word, is like a radar blocker !! I have posted on the Amazon product to ask if it is supposed to generate that much RFI - i cant believe they are allowed to sell something like that which generates some much RFI.

  7. An interesting read Jim, I ended up here as I've just discovered the source of new PLT interference is pair of TP-Link AV600s recently installed next door. What I was surprised about is how wide band they are, these ones seem to be notched on HF amateur bands but not 50MHz or 70MHz.

    I use a log Periodic so have good performance across low VHF but these things are almost under the aerial so impossible to null out. Beam towards the house and the SDR waterfall lights up like strobe light!

    Luckily for me my neighbour is happy for me to come up with an alternative solution so I'll check out that repeater you've linked too. Worth spending a few quid to regain a quiet spectrum.

  8. Hi Paul
    Oh, they are wideband OK ...
    As you say notching is poor at 50MHz and non-existent at 70MHz. I also thought that they might not go up that far, but they do. There is still one pair nearby but they fortunately run out of steam at 50MHz. I think those ones have been in use for 10 years or more so not much help even if they improve them as the old ones with be with us for decades.
    The repeater is a good way to go and not so expensive that it is not worth trying - but be careful that the Ethernet cables do not radiate.
    Somebody suggested that Netgear Powerline 500s were not so bad. I tested this and found it to be true but I do not recommend them as they were not very good PLAs. They stopped working at very short range.
    I still have two of the repeaters in two houses, one on each side, plus my own one which happliy captures Britbox with no buffering. Why does anybody fit PALs in a house with wifi?
    Good luck.
    73 Jim

    1. Hi Jim, I've just spent the afternoon next door hopefully solving my QRM. The reason for their install was 'poor download speed' at the Sky Q box plus they are typical end users who don't really understand techy stuff but are swayed by flashy websites. So, no matter that they could actually watch on demand stuff their phone app showed relatively low download speeds of 20MBPS when in the front room and their reference point was the amount of buffer on a download (which used to be a lot more apparently). I have to resist the urge to go in and say you really don't know what you're talking about and don't worry about it but that wouldn't have got me very far had I done so!

      So here's what I found, BT drop wire enters front room and hits an old junction box and an old ethernet cable takes the pair to the new OR master socket in the back room where the router is. After some deliberating my fix was to move the master socket to the window sill entry point in the front room, connect directly to the router which is now about 3M from the Sky box. So, much better buffer on the download display which keeps them happy and decent download speed on the laptop in the back office. Signal reading is a bit mediocre 1-3 bars on the windows wifi symbol but speed tests hit 35MBPS, I've said if it becomes an issue I'll fit a repeater half way as they don't need top speed in the office, just a reliable signal. I'm keeping everything crossed it continues to work! With any luck the TPlink units are being returned as not working properly.


  9. erm .. PLAs not PALs. That is dog food.

  10. Paul
    I think you have done very well. Diplomacy is the best tool in the box for these things.
    I had a somewhat similar experience with one of the neighbours where I could move the router in the first instance. However, she later found whe wanted to use her laptop in her bedroom, wanted the router moved back for better coverage, and that was where the extender came in.
    Moving the BT box is a good plan. I think that there are a lot of old BT boxes in the wrong places, hangovers from old technology.
    The other neighbour on the other side still has one PLA. I can hear it on 6m. The question is - how much can I rely on their co-operation. Latest news is that they have got a new BT modem but do not want to instal it until after the lockdown in case they get into a pickle with the installation. I offered help and they say they will take me up on that. We will see ...
    I still reckon Sky could have avoided a lot of this by better technology and better training of the installers. Some of the installers are very good indeed, others are not.
    Hope it stays working well.
    73 Jim