Posts Tagged ‘PLT’
PLT Devices – Have I welcomed the Devil in to the shack?
January 1st, 2016 | 
Author: 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.
Conclusion
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.
PLT Devices – Have I welcomed the Devil in to the shack?
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.
Conclusion
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.
PLT debated in parliament
The issue of interference to short wave from power line networking devices was debated in Parliament yesterday. You can view the televised debate here. It’s quite long, but worth watching if you can spare the time.
If you don’t, here’s a summary: The only complaints are from a few hobby radio amateurs and the number of complaints has been too few to justify banning a technology that brings potential benefits to millions of homes.
Other points: “Hobby radio amateurs are not legally entitled to a completely clean radio spectrum”, and “no specific limits on interference levels have been set so that radio users can adapt as the use of PLT technology evolves.” It is also projected that the number of installed PLT devices will quadruple by the year 2020. So this spectrum-destroying interference will be coming soon to an antenna near you!
I’m afraid that the writing is on the wall for amateur radio. In today’s world, the only things that count are money and big business vested interests. There are too few radio hobbyists to count at the ballot box and they don’t contribute anything to the country that can be measured in financial terms. So we are just going to have to “adapt” to increasing interference levels by giving up hope of receiving weak signals, confining our activities to quiet portable locations, or using modes like D-Star which are interference-free once the signal level rises above the noise threshold.
I think we just saw a death sentence passed on our hobby!
PLT debated in parliament
The issue of interference to short wave from power line networking devices was debated in Parliament yesterday. You can view the televised debate here. It’s quite long, but worth watching if you can spare the time.
If you don’t, here’s a summary: The only complaints are from a few hobby radio amateurs and the number of complaints has been too few to justify banning a technology that brings potential benefits to millions of homes.
Other points: “Hobby radio amateurs are not legally entitled to a completely clean radio spectrum”, and “no specific limits on interference levels have been set so that radio users can adapt as the use of PLT technology evolves.” It is also projected that the number of installed PLT devices will quadruple by the year 2020. So this spectrum-destroying interference will be coming soon to an antenna near you!
I’m afraid that the writing is on the wall for amateur radio. In today’s world, the only things that count are money and big business vested interests. There are too few radio hobbyists to count at the ballot box and they don’t contribute anything to the country that can be measured in financial terms. So we are just going to have to “adapt” to increasing interference levels by giving up hope of receiving weak signals, confining our activities to quiet portable locations, or using modes like D-Star which are interference-free once the signal level rises above the noise threshold.
I think we just saw a death sentence passed on our hobby!
PLT a threat to British intelligence gathering?
A report produced for the British intelligence gathering organization GCHQ claims that noise from power line networking devices is causing a detectable increase in interference at its monitoring stations and could adversely affect its operations. The report, which can be found on the website Ban PLT, was originally released by GCHQ’s Director of Engineering and Technology but has since been disowned by GCHQ which now claims it contained “inaccuracies.” The government organization also forced the online tech news journal The Register, which published an article containing details of the report, to remove the author’s identity from the article using measures designed, ironically, to suppress information that could be considered a threat to national security. So much for freedom of speech.
Ofcom meanwhile continues to deny that PLT devices cause a problem, stating that there have been “only” 272 complaints of interference (all from radio amateurs) and that of 233 cases referred to BT all but one have been resolved so there is nothing to worry about. Has pressure been brought from on high to force GCHQ to disown the report which is embarrassing to BT which has a couple of million of the Comtrend PLT devices installed nationwide? It is blatantly obvious that Ofcom couldn’t give a damn about the possible effects on a few hobbyists who don’t even pay a license for the spectrum they use. But a threat to the country’s ability to monitor the short waves to gather intelligence about potential security threats is something they would have had to take seriously.
PLT a threat to British intelligence gathering?
A report produced for the British intelligence gathering organization GCHQ claims that noise from power line networking devices is causing a detectable increase in interference at its monitoring stations and could adversely affect its operations. The report, which can be found on the website Ban PLT, was originally released by GCHQ’s Director of Engineering and Technology but has since been disowned by GCHQ which now claims it contained “inaccuracies.” The government organization also forced the online tech news journal The Register, which published an article containing details of the report, to remove the author’s identity from the article using measures designed, ironically, to suppress information that could be considered a threat to national security. So much for freedom of speech.
Ofcom meanwhile continues to deny that PLT devices cause a problem, stating that there have been “only” 272 complaints of interference (all from radio amateurs) and that of 233 cases referred to BT all but one have been resolved so there is nothing to worry about. Has pressure been brought from on high to force GCHQ to disown the report which is embarrassing to BT which has a couple of million of the Comtrend PLT devices installed nationwide? It is blatantly obvious that Ofcom couldn’t give a damn about the possible effects on a few hobbyists who don’t even pay a license for the spectrum they use. But a threat to the country’s ability to monitor the short waves to gather intelligence about potential security threats is something they would have had to take seriously.
