PLC at Mannheim, Germany

Interferences instead of shortwave broadcast
Dipl.- Ing. Ulfried Ueberschar, DJ6AN Dipl.- Phys. Thilo Kootz, DL9KCE Listening to shortwave broadcast stations in parts of the city of Mannheim is almost impossible. This article describes a measurement campaign, including the experiences related to it.
Translated by Karl Cornelius
NB 30 and Radio Regulations
NB 30 (Nutzungsbestimmung 30) is an article of the national German frequency assignment plan. It defines some conditions for frequency usage within wire based telecommunication installations. According to NB 30, emissions of wire based telecommunication installations are allowed up to a certain radiation limit level, under the condition, that no interference to radio service occurs. Of course, in case of exceeding the limit, operation is not permitted at all. Even more: As is stated in the Radio Regulations (RR) Article 4.11, the member states of the ITU (which have signed this international treaty more than 180) have accepted that, among those frequencies, bearing the possibility of wide radiating radio traffic, those ranging from 5 MHz to 30 MHz are suited in particular, and so oblige, to undertake any measures for a protection of these frequency bands, used by the abovementioned traffic. Oct. 3. 2003 has been giving a talk to the fraction of the local council of the city of Mannheim concerning the untenable situation of harmful interferences, originated by PLC. Following on that, on Oct. 29. 2003, Peter received a note from the above auditory, saying that: in the meantime MVV Energie (a local energy supplier) called us, telling that the radiointerference (.) at the time, takes place in a close agreement with RegTP. MVV Energie though made a remark, that until today, no case of a any confirmed PLC interference had been reported europewide so far, as experienced by a radioservice, to be protected.
t seems to be obvious that a first step into the electromagnetical chaos has been realized by now. 230 Volt powerlines are undergoing a mutation into transmitting antennas, to be present anywhere and at any time. Highfrequent modulation signals, as generated by the datastreams of broadband telecommunication applications, are leaving the inhouse powerline cabling of road blocks via unsymmetrical and unshielded cable routings. On listening to shortwave receivers, signals not only from DX stations, but even those of broadcasttransmissions in the frequency range of
but nothing untried, to protect radio frequencies, that have been allocated on the base of Radio Regulations. The interference potential of a PLC system, installed and operated at Lutherstrasse of Mannheim, that we finally should learn about on November 26./27. 2003, may but exceed all premonitions.

Interference included

Jetzt Dosenwechsel! (change the Dose now! [Dose, in a common sense in germany meaning the wall socket/ power outlet of the electrical installation system, for instance in a living room)]. That is what the advertisement at www.vype.de s internet homepage calls for, offering the alternative use of a power outlet as an internet access. The customer receives a starter kit, containing a Vypebox (modem), 5 e-mail addresses, 5 MByte of web space for his homepage, USB as well as an Ethernet cable, CD-ROM and a USP driver set. Included for free, but not mentioned at all, are the interferences to be expected by a common usage of frequency ranges, already assigned to shortwave radio services. The interferences add on to the fieldstrengths of those services due to powerlines, having mutated to transmitting antennas, as tried to be demonstrated here. Measurements, in addition, also have been accomplished on November 27. by an investigation of the Regulierungsbehrde fr Telekommunikation und Post (RegTP) [the authority taking care of regulations, that concern telecommunication- and postal matters in BRD], using an own equipment to carry out their measurements, and forwarding results on their offical way. Peter Roselieb, DL9KBM, member of staff politics contacts of DARC, on
Figure 1: OM Sandor on giving a try to receive the Hungarian Broadcast of his homeland. Nothing to listen to except for clatter and cracking
2 MHz to more than 20 MHz are superimposed by a continuing PLC interference spectrum, finally being unreadable. Fieldsimulations, performed by high schools, forecasting on a sound technical base, with the apprehension concerning of broadcast stations being unable anymore to fulfil their providing tasks they are obliged to, and even international petitions of radiotechnical stakeholders participating workshops, held at Brussels on October 16. 2003, all of them leaving

Shortwave-broadcast unreadable
To OM Sandor, a shortwave listener and radioamateur born in Hungary, it is a matter of course for about 25 years, to be
nals received from other services, as for an example amateur radio, have been unidentifiable in the pecking of the interfering modulation.
Interferences made visible
When staring, it did not seem to be too easy at all, to make the distinctive interference modulation listened to, even visible on the monitor of the spectrumanalyzer. A hint, given by Ingo Dittrich, DK9MD, saying, that the persistence of some single spectral components might be too short, and could be caught only by using the instruments max hold facility, led to a success. By thus, we were now able to make measurements for a later on evaluation, taking data from both, the dipole feeder and a portable selective antenna at Sandors living room. Furthermore, and by using a high pass, having a 2 MHz transition, we also performed measurements bet-
Figure 2: Before the introduction of PLC at the city of Mannheim, Sandor was able to receive broadcast via the telescopic antenna of his receiver. Now it is almost impossible even by using a sloping-dipole, ten by ten meter
linked to his home country via shortwave. Hungarian- and germanspeaking broadcast stations in the 41 meter and 49 meter band have always been a necessary means of information to him. Experimental amateur radio assisted his entry into telecommunication techniques, also being a reason for further technical education. Today, he only may receive Vype signals on his shortwave radio. For this reason, he made contact to DARC e. V. and set up an interference report to be sent to the appropriate subsidiary of RegTP, that immediately reacted with the announcement, to visite him for taking measurements. OM Sandor invited us for a support.
made it possible, to at least understand the contents of any modulation. We happened to be speechless. Never before, had we expected such a far reaching influence of PLC.

Measurement task

RegTP had advised its visit for the next day, a good reason for us, to take the opportunity of already performing several measurements at Sandors living room in the afternoon and evening of this day. Measurement equipment would be the R&S FSH 3 calibrated spectrumanalyzer, assisting us in inspecting those frequency ranges to be interfered, and putting their fieldstrength and its resulting receiver- (analyzer) input levels respectively, into a relation to the wanted signals of radioservices. A first listening impression was already achieved by using Sandors shortwave receiver, a Grundig Satellit 3400 professional, with a built in telescopic antenna, as well as with a 10 by 10 meter dipole, mounted outside (figures 1 and 2). Never at all before had we been so stunned, standing in front of a shortwave receivers loudspeaker, as at this very moment. Regardless, to what frequency between 2 MHz to 20 MHz the dial pointer was moved to, and disregarding modulation whether to be AM or SSB, a pecking interference signal superimposed each Kilohertz to be received. Using the dipole, radiobroadcast on the 41 meter and 49 meter could be picked up out of the interference floor so, as to be at least readable again. Sig-

PLC in The area of the city
On driving to Mannheim by car, and accompanied by our mobile test equipment, we have been deeply impressed by the interferences, as experienced even already on one of the citys highway feeders, by watching some shortwave broadcast stations, in the 49 meter band, that we had been listening to before. While approaching the city itself, an intensive increase could be noticed, up to a level in the vicinity of the main railroad station, which made it almost impossible to Deutsche Welle as well as Radio Berlin to be received in a usable manner. Still having some sufficient time and, without any good knowledge of the city, by a driving through a couple of several districts, we recognized, that it was nearly impossible, to find a spot for the interferences to be attenuated to an amount, that
Figure 3: The PLC repeater as is installed next to the mains power point of the house
Figure 4: R&S HFH 2 magnetic loop antenna aids in measuring interference levels at Sandors kitchen according to Measuring regulation MV05
Figure 5: Ten by ten meter dipole, receiving level at the spectrum analyzers input, Max Hold sweep operation, markers 1set to 6.6 MHz and to 2 to 7.1 MHz. Spectral lines generated by PLC and almost without any gap covering the frequency range of radio-services up to 7.1 MHz, thus causing harmful interference as according to Radio Regulations 2001, article 1, Sect. VII 1.169, in the 41 m broadcast band. And making only very strong signals identifiable
Figure 7: To check, in how far one still might be able to receive radiobroadcast in a living room with the telescopic antenna, coming with a portable radio receiver, an RFT FSA 101 tuned ferrit antenna with an activated, 10 db preamplifier and a frequency range of 2 to 20 MHz has been applied to the analyzer input. (Markers in this measurement example at 6.8 MHz and 7.8 MHz resp.) As a result, PLC spectral lines cover, again without a gap, the complete range of radio services within the bandwith of the FSA 101. That leads to the conclusion, that, within a living room, and under the circumstances as they have been described before, it is impossible, to receive signals, emitted by radioservices. Even more, it results in an exclusive reception of harmful interference signals as a consequence of the common usage of frequencies in the basic sense of Radio Regulations 2001, article 1, Section VII 1.169
Figure 6: Ten by ten meter dipole, receiving level at the spectrum analyzers input, swept w/o Max Hold, markers positioned to 5.9, and 6.2 MHz respectively. Harmful interferences as to Radio Regulations 2001, article 1, Section VII 1.169, can be listened to acoustical. PLC spectral lines but not visible due to the sweep time of the analyzer being too fast and its resolution bandwith too small in relation to the short repetitionrate of the spectral lines themselves. That makes it possible, reading the basic signal level to be achieved w/o PLC, which, with its 13 db[V] (about S6) is not amazing

Figure 8: Ten by ten meter dipole, level received at analyzer input, zero span, center-frequency 7 MHz. The reason for PLC interferences as a result of the property of digital levels to rise and fall, (data bits) may be recognized extremely well by a time/amplitude monitoring
Measurement Results RegTP
Frequency [kHz] X-Axis db[V/m] Y-axis db[V/m] Z-axis db[V/m] Max db[V/m] Max. corr. db[V/m] Limit level db acc to NB 30 Exceeded db 32,50 38,69 33,15 35,29,89 26,5 Measurements taken in the kitchen of Sandor in 3 Axis (column X, Y, Z) after a geometrical addition resulting to a maximum value (column Max). These values have been corrected for a measurement distance of 1,3 meter instead of 3 meters and for using quasi peak instead of peak weighting, as they did not correspond to measurement conditions of NB 30. This last correction is take into account by the numbers of column Max. corr. Basic level has been defined with 26 db[V]/m. PLC adding to it up to nearly 40 db, exceeding the given limits by far. Frequency [kHz] X-Axis db[V/m] Y-axis db[V/m] Z-axis db[V/m] Max db[V/m] Max. corr. db[V/m] Limit level db acc to NB 30 Exceeded db 35,10 32,67 32,50 34,68 33,22 34,29,89 20,9 Measurements have been taken on the pavement in front of the house (calculation, correcting and weighting as by the above). The exceeding of the limit levels being considerable again.
ween the phase and guard as well as between the NP and the guard of the 50 Hz mains. An 80 meter portable direction finding receiver, made available by our ARDF department, including earphones, led us to the confirmation of a very interesting phenomenon, as already observed by some UK radio amateurs. All of the conducting objects, when connected to the ground (what could be the mast of a lantern, a rain pipe, or a metal scaffolding), could, by the direction finding receiver, be detected to be behave like emitting wave guides for the PLC interference spectrum. Each line of the spectrum, depending on its frequency, by this way is finding its own resonant wave guide being also true as well for any telecommunication networks and antenna installations. Sandor explained to us, that the PLC repeater had been installed close to the three phase mains powerpoint of his house (figure 3). On looking for this device, we made acquaintance with the house manager. She wanted to know what those strangers were looking for in her cellar. By telling the reason of that, she explained to also have experienced strong interferences on radio receiving, right now planning to give away the equipment to undergo a repair.

asked for the frequency ranges to be interfered, made audio recordings by using the output of the Grundig receiver, and performed field strength measurements on all 3 of the magnetic components of the interferences, emitted by the 230 V powerline. Destination of the powerlines symmetry and a couple of different outside measurements, made in a distance of 3 meters to the outside walls, were the main focus of their work. All of our questions have been responded to and answered friendly and competent, but telling us, any possible decisions to be a reaction to the results of the measurements performed, might be expected as to come from above.

Literature

[1] Radio Regulations, Ausgabe 2001 (VO-Funk) [2] Telekommunikationsgesetz TKG, 49 as applying now [3] Messvorschrift RegTP 322 MV05 Ausgabe Nov. 2001 [4] Messbericht von Inhaus-Modem (Modell, Develo), Ingo Dittrich, DK9MD, 14. 12. 03 Bericht und Erfahrung mit fnf verschiedenen Inhaus-PLC Modems, Thilo Kootz, DL9KCE, both published at: www.darc.de/aktuell/plc [5] downloads available at: www.darc.de/aktuell/plc with audio recordings of the interference situation experienced by Sandor [6] web site by VSV concerning PLC www.powerline-plc.info [7] Horst-Dieter Zander, DJ2EV: NB 30/mv05 und Strfallregelung, Funkamateur 4/02, S. 770 [8] Wendelin Reuter, DK6ZD: Powerline Communication (PLC) gefhrdet Funkdienste, CQ DL 11/03, S. 770 [9] Horst-Dieter Zander, DJ2EV: Powerline Communication (PLC) ein Zwischenbericht, CQ DL 10/01, S. 716 [10] Alexander Schwarz, DL3KH, Bernd von Bojan, DJ7YE: Rauscht PLC bis nach Australien?, CQ DL 6/01, S. 429 [11] Ulfried Ueberschar, DJ6AN: 59+ auf der Powerline, CQ DL 5/99 S. 364

Whats going to happen?

On January 6. 2004, OM Sandor called Mr. Walter Wagner (RegTP, Referat 511-7 of Hauptstelle Mainz), the appropriate person being responsible for interferences created by PLC at Manheim, by phone. The measurement results had been given to his attention for a judgement, commented as follows: an inquiry has been sent to the operator of the PLC installation action for an improvement of the interference level will be following a written statement can be expected by January 31. 2004. Sandor is waiting and hoping, while listening to the clatter and cracking.
The official measurements
Three employees of RegTP showed up on next days morning, carrying an R&S measuring receiver and a loop antenna, moveable all around of its axes, into the small kitchen (figure 4). They

The future

In Austria, the telecommunication authority, that is competent for the city
of Linz, already has forwarded the only order, that is in an accordance with legal communication laws, and thus being unambiguously: TURN OFF THE INTERFERENCE! Lets hope for a similar decision that points the way ahead, for Sandor and amateur radio.