9 posts • joined Thursday 12th August 2010 13:00 GMT
Netgear PLT review
Trendnet also have has a "500Mbps" product which doesn't appear to offer the advertised bandwidth - see:
Can you check if the products are based on the Atheros chipset. If they are, ask them for a reply on the following - Atheros don't seem to want to answer the questions:
"The documentation for the AR7600 / AR1500 refers to the RD-4700-GE Reference design which claims to be "Emissions Compliant" to "CE Class A and Class B".
I assume that you are referring to EN55022? Please could you confirm whether or not this is the case. During the last three years that I have been involved with PLC, I have neither tested nor seen test results indicating passing class A emission levels, let alone class B. All devices that I am aware of are +30dB over these levels. In fact the following Homeplug presentation categorically states that "Safety, immunity and harmonics are correct but almost all PLC devices pass over the CISPR 22 class A, B limits so failed the test and we could not generate (directly) the DoC (Declaration of Conformity) needed for Europe" See:
I am also quite concerned to see these devices operating at up to 68MHz. Please can you confirm which frequencies are notched in the spectrum 30MHz - 68MHz, as your products appear to operate across the Amateur 50-52MHz band which will cause a considerable amount of concern within the radio amateur community?
I look forward to your reply"
Thanks in advance
73 Richard M0SNR
quote verbatim: "Tried, and failed. The things kept on losing connection in our avetage 3 down, 3 up semi, and yes, the FM radio wipeout is all true. We were told it's just a handful of radio enthusiasts getting interference from these things. Well, I can confirm it affects your radio one listening (or whatever else you listen to) as well. Total wipeout in fact, which wouldn't have been so bad had they woprked properly!"
If Gbps PLT adaptors *don't* harm Radio 4....
Can you explain this, as well as interference to DAB?
Gbps PLT based on the Gigle chipset operate from about 2-30MHz and 50-320MHz. The HF spectrum is notched in the Amateur bands, but the VHF spectrum in current products are not notched at all. The can lead to interference FM (whole band), CAA VHF and DAB to name a few services.
Gbps products have been tested in a UKAS laboratory and consistently fail EMC test specs that they claim conformance to. I can back up my argument; can you?
Also, I'd be interested in seeing a Reg Hardware test of these Gbps devices and actually demonstrate under real-world domestic conditions that the devices actually achieve anywhere near the throughput that they claim.
What is interesting is that domestic wiring and spurs become of resonant lengths at VHF, which means that a given Gbit PLT in the real world produces a non-deterministic RF transmitted spectrum from the wiring.
I really don't understand - apart from distribution sales (and I get the impression that margins are low) there is no money for Europe apart from Ofcom making money for interference complaints!
As a commercial engineer, working in the real world, I cannot see any reason for PLT being allowed on the market. I might get a pair, up the clock so that they are running on a TV MUX and bollocks to any complaints (I know it wouldn't work but it's a dream)
PA Report and ineptitude.
The PA report states that there is a serious EMC issue and the only solutions to eliminating EMC issues caused by PLT don't exist and have not been proven (smart notching and power control).
How is a junk PLT device going to be sensitive enough to be able to detect a radio signal using the house wirng as an antenna, and then determine if it's AM, SSB or DRM? It's a joke! Is a crappy PLT supposed to be as sensitive as a £2k receiver. Either way, tuning across broadcast bands would just be a sea of PLT noise interjected with the occasional broadcast station which would not be a pleasant listening experience, either on Short Wave or FM.
Most importantly, the PA report failed to take into account intermodulation effects, where deliberately notched-out spectrum by a PLT can be filled by the PLT's emissions impinging on other mains equipment, primarily Switching PSU's.
The limited amount of testing with a set of Belkin 1Gb devices that I conducted here demonstrated that the length of mains cabling between the PLT's altered the interference spectrum, which is quite understandable. Again, this has not been addressed by the PA report.
The PA report is flawed and the investigation into the effects on VHF appear to have been rushed.
I've yet to see a PLT reach anywhere near 1Gb and given Shannons Law, I'd love to see the spectrum that it would use to achieve it :)
Ofcom say that they have no power? Remember this story? http://www.theregister.co.uk/2009/10/28/ofcom_pilots/
PLT DELIBERATELY uses CAA spectrum.