RADIO SPECTRUM COMMITTEE RSCOM03-12
Source: Finland
Date: 23 May 2003
Item: Interference caused by Power Line Communications
1. Field tests performed in Finland
FICORA has measured 3 times EM radiation from PLC network. Measured field levels at 3 m
distance are shown below from two measurements.
Figure 1: PLC network in Turku, Ascom system, 15.4.2003
PLC outside @ 3 m from transformer cabinet
65,0
60,0
NB30 limit
E(dBuV/m)
55,0
50,0
Background, Data off
45,0
Data on, factory default
power
40,0
35,0
Data on max power
30,0
25,0
20,0
0,0
10,0
20,0
30,0
f(MHz)
PLC inside at entrance of block-house
55,0
50,0
E(dBuV/m)
45,0
NB30
40,0
Data off
35,0
Data on, max data power
30,0
25,0
20,0
0,0
10,0
20,0
f(MHz)
30,0
Figure 2: PLC network in Vantaa, Mainnet system, October 2001
90
80
70
dBuV/m
60
In-House, File
transfer
NB30
50
40
30
20
10
0
0,0
10,0
20,0
30,0
F(MHz)
60,00
50,00
dBuV/m
40,00
Outside, File transfer
30,00
NB30
20,00
10,00
0,00
0,0
10,0
20,0
30,0
F(MHz)
Listening tests with sound broadcast receiver at the environment of measurements in Figure 2
(Mainnet system using DSSS modulation) revealed that interference was very annoying on the
band from 3 MHz to 22 MHz.
2. Proposed limits for PLC
Starting point for the limit setting should be the protection criteria for HF radio services, not the
signalling level needed by the PLC industry. If we look for example the broadcasting, the
protection criteria and starting point would be the planning data used by broadcasters.
Following planning criteria’s are used for minimum field strength at target area:
On MW band: 57 – 65 dBuV/m
On HF band: 38 – 50 dBuV/m
Indicated field strengths assume 37 dB rf signal to noise ratio, which provides still reasonable
reception quality.
For PLC there have been proposals to allow radiated field strength around 55 dBuV/m at 3
meters. This would be the same level as is used for HF BC planning criteria. If the value 55
dBuV/m would be allowed, then for broadcast reception one would need a level of 55 dBuV/m
+ 37 dB S/N = 92 dBuV/m. This level is around 40 dB more than is planning criteria. Distance
to the transmitter would need to be reduced to 1/100 to give the same quality of reception.
Obviously there would be no “sharing” with radio users and PLC, if PLC would be allowed for
proposed 55 dBuV/m at 3 meters.
EN55022 sets a limit for radiated fields from 30 MHz up to 1000 MHz, at 30 MHz limit is 30
dBuV/m at 10 meters.
One should also take into account that for broadband interference like PLC, the limit should
not be based on present EMC standards, which all are drawn assuming interference to be
narrow band nature.
3. CONCLUSION
PLC is not compatible with HF radio services with proposed limit of 55 dBuV/m at 3 meters.
If PLC would be promoted for political reasons and allowed to use signalling levels as
requested by PLC industry, we should declare that radio reception is not anymore protected in
the areas where PLC is used. Only remaining issue would be the protection of safety services
on HF band. But this can be handled on a national level.