The house using PLC(red)Receiving points (numbered black circle)
10255kHz [11-JAN-2007] Panasonic HD-PLC Noise, Point 1->2->3 on the map (Japanese remarks inserted at point 1, 2 and 3.) The PLC noise is loudest at the point 2 about 30m away from the house using PLC. The noise is audible even at the point 3 about 50m away from the house.
CNC-1000 (HomePlug).Measured by 1m short diple antenna with post high-Z differential amplifier at 10m from the house. Horizental polarization at 2m above the ground.
The receiving antenna factor (taking the post amplifier gain and coaxial cable loss into account) is 4dB. Therefore the field strength [dBuV/m]=(vertical axis value [dBm]) + 107 [dB] + 4 [dB].
Japanese regulation is supposed to suppress the field strength as low as 28 [dbuV/m] for 2-15MHz and as low as 18 [dBuV/m] for 15-30MHz at a distance of 10m from the house with PLC. The observed field strengths, 35 [dBuV/m] at around 7.8MHz exceeds it 7dB, 32 [dBuV/m] at 18.5-20.5MHz exceeds it more than 13dB. The field strength (green) exceeds the ambient noise level (blue) more than 5dB for almost entire spectrum of 7.5-20.6MHz and OFDM carriers are clearly observed .
PLCs connected to AC outlets, idle (blue)
Sending file from outlet1 to outlet2 (black)
Sending file from outlet2 to outlet1 (green)
Netgear (UPA).Measured by 1m short diple antenna with post high-Z differential amplifier at 10m from the house. Horizental polarization.
The receiving antenna factor is 4dB. Therefore the field strength [dBuV/m]=(vertical axis value [dBm]) + 107 [dB] + 4 [dB].
Japanese regulation is supposed to suppress the field strength as low as 18 [dBuV/m] for 15-30MHz. The observed field strength 30 [dBuV/m] exceeds it more than 10dB.
PLCs disconnected from AC outlets (black)
PLCs connected to AC outlets, doing nothing (blue)
File transfer using PLCs (green)
Thousands of radio amateurs, shortwave listeners, radio astronomers and myself have been opposing to this faulty deregulation. There are too many problems. However since we do not have enough time, I would like to focus on the most serious flaw of the Japanese PLC regulation. It is not defined in terms of the emmited field strength.
The Japanese in-house PLC regulation only regulates the common mode current directly injected from the PLC modem to the AC outlet. The government claims that the regulation could suppress the radio noise radiation from the PLC installations as low as which of the personal computers regulated similarly by CISPR22. However this is a total lie.
To explain this, I have to refer to CISPR22. CISPR22 certainly regulates both the power port noise and the communication port noise of personal computers in the similar way by common mode current noise. This is very tricky but reasonable. Communication line is highly balanced and has no branches. Therefore differential to common mode conversion will not occur. In that case, the only radiating current is the common mode current injected from the personal computer's communication port.
On the other hand, in-house power lines, in particular, the branches which have switch and lamps (called switch branch) are quite imbalanced at HF and could convert differential mode current into common mode current. However since differential mode current at HF is not injected from the personal computers power supply (because it could be easily shunted by bypass capacitor), there will be no converted common mode current. Therefore the only radiating current is again the common mode current injected from the power supply. Please note that the reasons why we don't have to worry about the common mode current converted from differential mode current are different for power port and communication port.
In the case of PLC, neither of the above two logics work. The large differential HF signal is injected to in-house power lines including lots of switch blanches which convert differential mode current into common mode current. There are two origins of HF radiation. One is from the common mode current directly injected from PLC modem to AC outlet, which is regulated by Japanese PLC regulation in a similar way as CISPR22. The other is the common mode currents created at the switch branches from the differential mode current injected from the PLC modem to AC outlet. The latter is not at all regulated by the Japanese PLC regulation. And even worse, the latter is the main cause of HF radiation from in-house PLC installation.
They claim that the latter is already taken into account as the low LCL of AC outlet. However it is completely wrong. Here is a counter example: suppose you connect dipole antenna to the AC outlet, the common mode current at the outlet does not increase as the dipole antenna is perfectly balanced. However the DIFFERENTIAL mode current injected into the outlet is converted into antenna current and radiated quite efficiently. Therefore theoretically they are completely wrong.
Japanese PLC regulation has no scientific basis and fails to suppress the radio noise from the PLC installation below the ambient noise level against its claim.
The similar problems had been already pointed out in 2003 CISPR, as "Application of the LCL method to measure the unbalance of PLC-equipment connected to the Low-voltage Distribution Network" by J. Verpoorte. Please read the Conclusions of this paper carefully. The principle of the current Japanese PLT regulations had been dismissed in CISPR three years before it was adopted in Japan.
Prof. Masahiro Kitagawa, Ph.D Graduate School of Engineering Science, Osaka University 1-3 Machikaneyama-cho, Toyonaka, Osaka, 560-8531 Japan
kitagawa(atmark)es.osaka-u.ac.jp TEL: +81-6-6850-6320 FAX: +81-6-6850-6321 ROOM: D419