PLT Devices – Have I welcomed the Devil in to the shack?

I joked recently about turning to the Dark Side, well my conversion really was complete after the Boxing Day sales.

I need to set up the ability to remotely operate the station via the internet as well as experiment with internet linking systems but the wi-fi link to the shack isn’t fast or reliable enough. Now if I do a scan looking for wi-fi networks I can see well over a dozen, some of them quite strong and more are popping up all the time and I suspect this congestion is part of my problem.

The Samsung Smart TV in the house was also wi-fi linked but we were having increasing issues with the BBC iPlayer and Netflix with buffering or poor quality images because of poor signal and data rates.

Ideally I would be like to fit proper ethernet cables but it is totally impractical without major upheaval or unsightly trunking a definite no-no. In the end the only workable and affordable solution seemed to be to get some of those evil Powerline Transmission (PLT) devices.

I have suffered strong sporadic QRM myself which I have assumed were neighbours PLT networking devices as I’d read the horror stories, seen the videos and anecdotal reports of mains borne noise caused by them. So I hadn’t even considered it until I saw a post and video by Dan Trudgian (M0TGN) about his experiences of using some Netgear devices and the apparant lack of interference to his radio activities. Some members of South Kesteven ARS had also started using them, so I took the plunge and ordered some Netgear ones reduced on Amazon in the Boxing Day sales.

Setting them up was easy, but the acid test was how much noise did they generate? I set up one device in the shack at the far end of the mains cable run to maximise radiation. Streaming internet radio and a HD movie on Netflix I then used the FUNCube Dongle PRO+ SDR connected to the OCFD to see what noise they were generating.

Here are my observations going through the various HF bands. Where noise is present I first stopped the streaming and then powered off the devices to eliminate them as the cause, where they were the cause it seemed eliminating the network traffic was sufficient to greatly reduce the effect.

80 Meters

While the antenna isn’t optimised for 80m, signals can be seen as well as noise. Before you get excited this noise has been present for quite a while and isn’t being caused by the new Netgear devices. This noise is what I suspected was generated by PLT devices used by my neighbours.

60 Meters

Shocking noise but again this isn’t caused by my new devices, the noise has the same characteristics as that seen on 80m.

40 Meters

The band was busy, there is some noise again but not from the new devices, this was looking encouraging. I have also showed the adjacent broadcast band.

30 Meters

Again, largely noise free

20 Meters

Still largely noise free, the QRM that is present still wasn’t due to the new devices

17 Meters

This was the first indication of QRM from the new devices, however it appears effectively filtered to leave the amateur allocation clear. The faint noise in the middle picture is not from the new devices.

15 Meters

Again this band was clear of noise

12 Meters

Showing the two ends of the band again the clear signal/noise from the devices again seems effectively filtered

10 Meter

I didn’t observe any additional noise on this band, but unfortunately deleted the screen grabs 😉

So where was the QRM?

While the amateur bands appear to be filtered, the transmission can of course can clearly be seen on some non-amateur bands and apart from 16 meters seems to avoid the broadcast bands.


These Netgear XAVB5221 devices seem effective, indeed doing a speedtest in the shack was more than acceptable (the dire upload speed is a ‘feature’ of my cable ISP)

This fairly rudimentary testing has largely given me confidence that they won’t be any issues. The band conditions weren’t brilliant when I did test, but even with the absence of signals on the band any noise would be evident as seen. Yes they clearly do generate QRM but thankfully not it seems in the amateur bands. I haven’t heard any extra noise on any of the radios over the last few days so all is looking promising. I will keep you posted if there is any change.

Wireless Woes

It was always my intention when I had my workshop/shack installed to install a permanent wired network link, however I never did and now it would prove a logistical nightmare.

When I first got wired up to the Internet with Diamond Cable back in the late 1990s it was via a second telephone line fed in to the ‘computer room/study’ which in reality was the small ‘box/bedroom’ at the front of the house.

Diamond Cable became NTL/VirginMedia and with the introduction of proper broadband the Cable Modem naturally got installed in the same front bedroom. I have always had several computers networked together but mostly in the same room via cables.

I eventually got a router with wireless capabilities the ubiquitous Linksys WRT54G and gradually more and more devices have been linked wirelessly. Laptops, smart-phones, a modified original X-Box running XBMC to play videos on the TV, Netgear MP-101 media player and a Nintendo Wii. More recently my new Canon printer and Samsung SmartTV are now connected to the wireless network.

Over the years I have acquired different routers and access points but I kept going back to the WRT54G as it didn’t have as many compatibility issues and since the firmware was upgraded to Tomato and has proved to be rock solid. It covers the house reasonably well, but not so well at reaching the shack in the back garden, most wireless devices just give up. If they can see the network they seem unable to maintain a link.

When I fitted out the shack I was forced to find a solution. I could have gone out and got a wireless booster to fill the blackspot, but as I had a collection of various wireless routers/access points I investigated possible solutions that didn’t involve any expenditure. I made the assumption that the superior antennas and design of the RF circuits in the access points would overcome the range issue. I was sort of correct and in the end I managed to get a Netgear WNR2000 configured using WDS to connect to the main house wireless.

Sadly the WNR2000 is quite frankly rubbish and often needs to be rebooted to get the link established, when it works it is great but too often it doesn’t! The other major issue was the implementation of WDS will only work with WEP encryption.

WEP is potentially insecure, I was getting more and more concerned about this so when I finally deprecated the last remaining WEP only devices in the house I have switched to WPA, ironically I had hoped to use WPA2 but alas some devices are WPA only!

Doing this has broken the shack network so I was back to square one. During the recent forced clearout I found a forgotten Buffalo router, mind you looking back you can see why I had forgotten it.

Have aquired a Buffalo AP and frankly it is a total piece of shit, shit setup & admin interface and has just forgotten the admin password!
— Andrew Garratt M6GTG (@nerdsville) November 27, 2009

A quick check and joy of joy it turned out to be a WHR-HP-G54, a device supported by the Tomato firmware, so was duly flashed up to version 1.28

I have now got it setup as a Wireless Ethernet Bridge and seems to be working well (I may have been a bit harsh on Twitter back in 2009!) and seems more importantly to be relatively RF quiet compared to the Netgear WNR2000 A good result!

Now I have some connectivity should make next weeks 144MHz UKAC contest a little easier, if I can the 2m antenna sorted and work out how to use the logging program.

Oh and the picture at the top? From South Park “Over Logging (or The Day the Internet Stood Still)“a classic episode!