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BPL / QRM Problems - pt. 4
PLT & BPL Interference Studies by The RSGB Links To Some
RSGB Studies and Articles
DONATE on-line to the RSGB Spectrum Defence Fund at www.rsgb.org/defencefund/ **JOIN** The Radio Society of Great Britain - Representing the best interests of radio amateurs against PLT RSGB puts
pressure on Ofcom regarding power line adaptors
RSGB asks Government to adopt German standard NB30 for PLT/xDSL RSGB EMCC Position on PLT (pdf file) Background noise on the HF bands (word document) PLT Test Information including Sound Bites (pdf file) Notes on the Final Report of the RA's TWG on the Compatibility of DSL and PLT with Radio Services 1.6 to 30MHz Compiled by the RSGB for the benefit of Radio Amateurs (pdf file) Notes on the RSGB Investigation of PLT Systems in Crieff (.pdf file) PLT and the Future of the HF Spectrum - from RadCom Feb. 2003 (.pdf file) What PLT sounds like (.wav files) HF Ambient Noise Floor - RSGB Observations (pdf file) MORE RSGB Information Further Studies have been carried out by the RSGB's David Lauder in the RSGB's Radcom Magazine PLT / PLC
UPDATE.
PLT stands for Power Line Telecommunications. It is also known as PLC in Europe and Broadband over Powerline (BPL) in the USA. There are two types of PLT, Access PLT and In-house PLT. Access PLT delivers Internet services to customers via RF signals injected at the electricity sub-station or other convenient point. In-house PLT uses in-building electrical power wiring for networking home computers or for streaming digitised audio/video signals from home entertainment systems. So far, Access PLT has not been deployed commercially in the UK for various technical and commercial reasons although a few trials are being carried out in continental Europe. In-house PLT is technically a more practical proposition, and home powerline networking products are on sale in the UK under various brand names. Recent proposals by a major Internet service provider to offer powerline networking products have brought potential interference problems into prominence. Information on PLT has been provided by several RSGB EMC Committee members, particularly Robin, G3J0. In House PLT The following information about in-house PLT is based on home powerline networking products that are currently on sale in the UK. Powerline networking products with faster data transfer speeds are coming onto the market and interference from these may have somewhat different characteristics from current products. Many powerline networking products are designed to an industry standard proposed by the'HomePlug Powerline Alliance or are similar in regard to interference mitigation policy. The 'Home Plug standard takes steps to reduce interference in the amateur bands, although not all manufacturers of powerline networking products are members of the 'HomePlug Powerline Alliance'. It is important to note that the 'HomePlug' and similar standards are 'industry standards', that are not recognised by International Standards organisations like the IEC, or ETSI and are not legally enforceable. The situation regarding enforceable standards and EMC regulation of all PLT devices is confused - to say the least - and is a cause of concern to the RSGB and to our counterparts in other countries. The RSGB EMC Committee tested some home powerline networking devices and made a formal complaint to Ofcom a year ago about the apparent non-compliance to the EMC Regulations of some such products. We are still awaiting a response. We have also proposed to Ofcom that they put in place precautionary interference Regulations that would apply inter alia to all types of PLT systems. Ofcom has, however, refused our suggestion. A major Internet service provider is marketing an Internet Protocol TV (IPTV) service that is delivered via computer networks and a broadband Internet connection instead of using conventional TV broadcasting or cable TV distribution. It has recently come to the attention of the RSGB EMC Committee that there are plans to use powerline networking as one method to distribute IPTV round customers' houses. This in-house PLT system is believed to have programmable 'notching' facilities but to date, no information is available about injected power levels or the default notching frequencies. The Committee is investigating this matter and an update will be published when more information is available. It is to be hoped that any system marketed in the U K would have a mateur band interference reduction similar to HomePlug. Frequency "Notching"  Current inhouse PLT systems
operate in the H F band and, as mentioned
above usually follow the HomePlug (or similar) standard. These systems
can reduce injected power over a complete band of frequencies such as
an amateur band. This is sometimes described as 'notching' although
this
term could be misleading. The systems tested use frequencies from about
4MHz up to about 22MHz and the RF is injected into the mains between
phase and neutral. In order to reduce interference to amateur radio the
power is significantly
reduced in the international amateur bands including 7, 10, 14, 18, and
21 MHz. The notches, as generated at the powerline network adaptor, are
about 30dB deep but there is no notching for the HF broadcast bands
however, nor on the 5 MHz experimental amateur allocation. The graph shows the output spectrum of a typical powerline networking device that was tested by the RSGB EMC Committee. This shows relative power versus frequency with a vertical scale of 10dB per division. Powerline Network QRM The information in this section is based on RSGB3 EMC Committee tests using two pairs of powerline networking units produced by different manufacturers. In both cases, when the network was transferring data it was relatively easy to identify because the frequency notches provided a unique characteristic. Interference on any particular installation may sound somewhat different depending on the receiver bandwidth and detector type, the brand of powerline networking adaptor and the nature of the data being transferred. Interference is not evenly spread across the HF spectrum as it depends on how well the mains wiring radiates on a particular frequency. To identify powerline network QRM, it is advisable to select AM detection on the receiver and switch off the AGC. Adjust the RF and AF gains so the interference is clearly audible. Tune the receiver across one of the HF amateur bands which come within the mask 7, 10, 14, 18 MHz. (21 MHz is at the top end of the mask and may not give a clear result). For instance, if 14MHz is chosen, tune from about 13.5 to 15MHz and check that the interference drops very significantly within the 14 14.35MHz amateur band. When tuning outside the amateur band, it would probably rise by about 30dB in the space of 100kHz or so. For confirmation, repeat the test on as many bands as possible. The effect can be heard rnost clearly on the upper H F bands late at night when these are 'closed' for long distance radio reception. Where there are large off-air signals, as is often the case on 7MHz, the effect may not be so clear. The 7MHz band is notched for the US Amateur allocation of 7.0 to 7.3MHz. When a home powerline network is transferring data, for example a large file transfer, the radiated signals may sound like a 'frying' noise interrupted for a short time (about half a second) at random intervals. When the network is idle, with computers connected and running but not transferring data, the interference is much less noticeable. Typically there are regular short bursts of data due to network 'polling' and in some installations, these may be heard as sharp clicks every second or so, particularly if the network is nearby. Where a home powerline network is being used for occasional file transfer, this will make identification difficult without the cooperation of the computer user (if known). Where the network is used for gamiing or for in-house distribution of IPTV then interference will be more or less continuous and identification should be easier. If the characteristics of a particular source of interference are similar to those described above, indicating that a powerline network is a likely source, the next step is to use a battery powered receiver with a whip or short wire antenna to search around for the strongest signal. This may not be easy at H F as signals can travel some distance along electrical power wiring and may also be coupled onto overhead telephone wiring. Because a HomePlug type powerline network is notched for the amateur bands, interference may not be excessive if the amateur antenna is a reasonable distance from the house and electrical power wiring. If you are a short-wave listener, who listens to broadcast stations and a powerline network is installed in your house or next door, you will probably get interference if you use a 'consumer' type short-wave radio with pullout whip antenna, or you use a shortwave receiver with a wire antenna situated close to the house where the powerline network is installed. If you are a dedicated short-wave broadcast listener with a well designed antenna situated in the garden, well away from the house, there may not be noticeable interference on strong 'broadcast quality'signals, but interference will probably be noticeable between stations and on weak signals. The effect on the new DRM (Digital Radio Mondiale) HF broadcasting service is more difficult to assess in a simple listening trial. DRM reception is either near perfect or there is no audio output at all - that is, it'dropsout'. On moderately weak DRM signals the WMER SNR spectrum was reduced in the presence of powerline interference, and the tendency to 'drop-out' was increased. Reporting Powerline Network QRM If you think that you are experiencing interference from a home powerline network, please inform the RSGB EMC Committee by email or by post to the RSGB EMC Committee at RSGB HQ. Interference can also be reported directly to Ofcom by using the online reporting form on their web site. David Lauder. RSGB. Join The RSGB
RSGB Radcom Magazine **JOIN** The Radio Society of Great Britain - Representing the best interests of radio amateurs against PLT DONATE on-line to the RSGB Spectrum Defence Fund at www.rsgb.org/defencefund/ Community Broadband Project A new project in Solihull, West Midlands, plans to deliver free or subsidised broadband internet access to residents in council owned multistorey housing blocks. The connection from the internet service provider (ISP) to each building uses a wireless internet connection service called RedKite, from CI-Net. This is described as a 'Pre-Wi MAX' radio link. WiMAX is a new standard that uses microwave frequencies and it is not thought likely that WiMAX links will result in any amateur radio EMC problems. When the data signals reach each block of flats via a WiMAX type link, the data needs to be distributed to individual flats. One possible way to do this would be via 2.4GHz wireless LAN access points on alternate floors but, in the Solihull project, it is proposed to do this in-building distribution via the electrical mains, using some sort of home powerline networking products. Such 'in-house' PLT distribution systems are of concern to the RSGB EMC Committee because they generally use frequencies in the HF range and some of the signals are radiated by mains wiring. Depending on the type of equipment used, emissions of interference in amateur bands might be substantially reduced by'notching' but such a reduction does not apply to other parts of the HF radio spectrum such as international H F broadcast bands or the experimental 5MHz amateur allocation. The CE marking of home powerline networking products might be described as a 'grey area' (see below). A letter has been written to the Director of Community Services at Solihull Metropolitan Borough Council expressing concern about the EMC issues related to this project. C.E. Marking Of Home Powerline Networks Home powerline networking products are a type of 'in-house' Powerline Telecommunications (PLT / PLC) system that have previously been mentioned in EMC on a number of occasions. The RSGB EMC Committee has tested two different brands of home powerline networking products and found that, although emissions of interference in amateur bands may be within the EN55022 Class B conducted emission limits, emissions in HF broadcast bands and the experimental 5MHz amateur allocation appear to be far in excess of the EN55022 conducted limits. The RSGB EMC Committee made a complaint to Ofcom in October 2006 about 'CE' marked home powerline networking products. In our view the devices that we tested, which are typical of many others on the market, do not conform to the protection requirements of the EMC Directive, as implemented in UK law. In this respect we also noted that the revised EMC Directive 2004/108/EC, which has been implemented in UK law, not only continues the entitlement for broadcast reception, but also includes a similar entitlement for amateur radio. Ofcom correctly referred the matter to the German regulator on the Home Authority principle. It is likely that the man ufacturer used the Technical Construction File (T C F) approach to demonstrate compliance with the essential requirements of the EMC Standard. This approach can be used in the absence of the Harmonised European EMC Standard for such devices but a TCF could be challenged if it were considered to be invalid. Nevertheless, it is much more difficult to challenge a TCF than to non-compliance with a harmonised standard, so this could be regsrded as a loophole in the EMC compliance arrangements. As of June 2008, the EMC Committee was still awaiting a formal response to our complaint. As long as these devices are CE marked, import into the UK cannot be restricted due to the EU Directives on the Free Movement of Goods and Services. Thus unless the German regulator challenges the validity of the TCF, it appears that nothing can be done to prevent the imports. Home Powerline Networks And Filter-Less PC PSUs Further to the April PSU item, Robin, G3JWI has done some tests at his home QTH. As well as the RF interference tests mentioned in April 2008 EMC, Robin has also done some tests of the compatibility (or lack of compatibility) between home powerline networking products and filterless PC PSUs. Robin set up a home network between two PCs using powerline networking , products that send data via the mains. One PC upstairs was sending data to another PC downstairs on a different ring main circuit. Robin also fitted the filterless PC PSU featured in April 08 EMC into a third PC and connected it to the same ring main as the sending computer but in a different room. He used a piece of free software called Netmeter to monitor the speed of data transfers via the powerline network. He then transferred a large video file via the network and compared the data rates when the interfering PC PSU was unplugged and when it was plugged in and operating.  The results are shown above. The interference from the unfiltered switchmode PSU reduces the average data rate over the powerline network by about 65%. It is likely that different configurations will give significantly different results and in some cases the powerline networking may not work at all when the interfering PSU is plugged in. The results of this test may be significant for projects such as the Community Broadband Project mentioned above. It would seem that one unfiltered PC PSU in one of the flats could seriously affect the speed and reliability of internet connections in other flats, especially those that have the longest path via the mains wiring. Unless the relevant authorities take effective enforcement action against PC PSUs with no filtering, there seems to be a risk of the following scenario. Home powerline networking products become widespread and radiate interference over much of the HF radio spectrum, (apart from amateur bands, we hope). Then the sale of low cost PC PSUs with no RF interference filtering becomes widespread, due to a lack of enforcement of the EMC Regulations. These unfiltered PC PSUs would not only interfere with the HF amateur radio bands but also with home powerline networking products. Eventually, no one would be able to use the H F bands for any form of communication, whether by radio or by mains wiring. David Lauder. RSGB. Networking Over Home Power Lines Continues To Be A Major Threat To The HF Spectrum BT Vision A major internet service provider is marketing an Internet Protocol TV (IPTV) service that is delivered via computer networks and a broadband Internet connection instead of using conventional TV broadcasting or cable TV distribution. This service is called BT Vision. A typical B.T. Vision installation includes a BT Home Hub and a BT Vision V-box. In some installations, these devices are located in different rooms. Although it would be possible for the two boxes to communicate via a wired Ethernet network cable or a 2.4G Hz wireless network, BT is supplying home powerline networking devices to some BT Vision customers, about 250,000 according to some reports. This almost certainly makes BT the largest supplier of such devices in the UK. In autumn 2007, the RSGB President wrote to the Director of Technology Strategy and Development at BT Vision expressing the Society's concerns about this matter. There are at least two types of home powerline network adaptors that may be used with BT Vision systems. It seems that some meet the HomePlug specification while others use the DS2 chipset and do not meet the HomePlug specification. One model called Comtrend is considered by some short wave listeners to be noisier than other types. RF interference generated by home powerline network adaptors has been discussed on the BT Vision support forum and also on a Yahoo Technical group called UKQRM. EMC Question At BT AGM BT held its AGM in London's Barbican Centre on 16 July. The Chairman reported a profit before tax of £2.5 billion - up by 2% on the previous year - and expressed disappointment that the share price was still too low. Chief Executive lan Livingston said that Openreach now provided 28 million lines, of which 13 million were carrying broadband for BT and for 450 other ISPs. Broadband was now available on 99% of lines - a statistic that could only be bettered by Taiwan. He promised 100Mbps optical fibre to 10 million homes by 2012 if appropriate financial arrangements could be agreed. Shareholders questions ranged widely for more than an hour. Considerable concern was expressed about the sharing of user data with advertisers. Another BT shareholder who is an EMC expert questioned the propriety of the BT Vision product, which can use 'powerline adaptors' and whether these devices meet the requirements of BT's official procurement policy GS7. The full text of the EMC question was as follows: `The BT Vision product includes 'Powerline adaptors' that allow the BT Home Hub and the BT Vision V-box to be in different rooms. These 'powerline adaptors' are not certified to an official European Standard for electromagnetic compatibility as is required by BT's official procurement policy. As an expert who is active in this field, I know that BT's procurement policy is a responsible one that would not be lightly disregarded by most people in the industry. "At this time EN55022 is the European standard to which powerline adaptors should be approved. However the limits given therein do not match the ambitions for, high-speed powerline communications. Advocates of this technology have been campaigning unsuccessfully for a relaxation of the Standard for some 15 years. So far they have been thwarted by those anxious to protect short wave communications and broadcast radio from electronic pollution due to powerline communications. The outcome of this debate remains extremely uncertain and it cannot be assumed that products already being informally marketed will conform to whatever amendment to the Standard ultimately comes into force. My questions are; Are the Board happy that the marketing of 'powerline adaptors' is consistent with their corporate ethical policy? In the strategic plan for the BT Vision product, what contingency has been allowed for a product recall, in the event that existing regulations regarding noninterference to radio services are enforced? If contingency has been made does this include compensation for customers who have a contract with BT for the supply of an integrated broadband system that includes the use of 'powerline adaptors'? What is the level of exposure to these events?" The above shareholder's question had been submitted in advance and BT provided a written response and had offered to discuss this matter further outside the meeting. The BT Shareholder then asked the Chairman's permission to ask supplementary question. Permission was granted if the question was kept short. The BT shareholder first said that BT's satisfaction with its ethical position must be incomplete because the Adaptors could not possibly meet BT's own standard GS7. To be brief, he then said that he had recently discovered that there was a lot of bad publicity for BT Vision on the web, and mentioned two YouTube videos and a Yahoo Group called UKQRM. The BT Shareholder then referred to the phrase "working directly with customers when problems arise` in BT's answer and said that this was not enough since it was the customers' neighbours who had the problem, At this point the Chairman of the meeting cut him short, saying that this was too technical and he should talk to Gavin Patterson, Chief Executive of BT Retail, afterwards. The BT Shareholder later reported that he was pleasantly surprised to be given a chance to meet Mr Patterson after the meeting and to have a five-minute conversation with him. Topics discussed included how afflicted non-customers should complain. Raising this issue at the BT AGM gave it wider publicity although it seems that not all those present understood the technical issues of EMC standards and protection of radio communications including international HF broadcasting. Although amateur radio was not specifically mentioned in the BT shareholder's question, an item appeared in the Mail on Sunday on 20 July with the title `Radio goes ga-ga`. This ridiculed the BT shareholder's question and resurrected the 1960s Tony Hancock 'Radio Ham' TV programme image. HomePlug Specification HomePlug is an industry alliance of hardware and software companies, retailers and service providers that originated in the US. In the US, the Federal Communications Commission (FCC) has allowed current carrier systems 'for over 50 years. These allow mains power wiring to be used for communications in the HF range, subject to a limit of radiated field strength and on a non-interference basis with other radio users. 'Current carrier systems were originally narrow band but the FCC rules did not specify a maximum bandwidth and this apparent loophole has been expioited by systems such as Broadband over Powerline (BPL) and HomePlug which occupy a wide bandwidth. Such systems do not comply with existing European conducted emission standards EN55022. Nevertheless, since they have become established in the US, there has been pressure to relax the European EMC standards to accommodate HomePlug and similar systems. The HomePlug 1.0 specification defines 128 evenly spaced carrier frequencies in the frequency range 0 - 25MHz but not all of these frequencies are used. The band used is from 4.49 - 20.7MHz and 84 carriers (numbered 23 - 106) fall within the used band. Of these 84 carriers, eight are permanently masked to avoid amateur radio bands, which leaves 76 effective carriers available for data transmission. The bandwidth of each carrier is 195.3kHz and the modulation is Orthogonal Frequency Division Multiplexing (OFDM), which is similar in principle to digital audio and video broadcasting. The HomePlug carriers that are not used are carrier numbers 14, 15 (7MHz band), 30 (10MHz), 50, 51, 52 (14MHz), and 70, 71 (17/18MHz). This is sometimes called 'notching' of amateur bands although this term is not entirely accurate. It appears that most HomePlug devices are based on Intellon chips where the masking of certain carriers is fixed in the design of the chip and cannot be re-configured. In practice, the HomePlug 1.0 specification appears to give a moderate amount of protection to amateur bands although it does not protect the experimental 5 MHz amateur allocation nor the HF broadcast bands. The frequency range used and the sharp rise in signal levels outside the 7, 10 and 14MHz amateur bands are characteristics that help to identify emissions from a HomePlug type network. There have been some reports of cases where the amateur band 'notches' do not appear to be as deep as expected and this could be due to non-linear loads on the mains, such as rectifiers, or possibly some other interference source that is 'filling in' the 'notches'. The raw bit rate for HomePlug devices is usually 14Mbps but there is also a so-called 'turbo'version at 85Mbps and products using the more recent 200Mbps HomePlug AV standard are now available. DS2 Devices DS2 Powerline technology uses chips from a Spanish company called, DS2. The raw bit rate starts at 200Mbps although 400Mbps devices have been demonstrated. DS2 uses programmable 'notching' that allows manufacturers of home powerline networking products to decide where to put'notches'. It appears that this configuration can also be changed after the devices are installed by updating the 'firmware' held in 'flash' memory in the device. One DS2-based device is the Comtrend home powerline adaptor. These are used by some BT Vision installations. It appears that DS2 based devices can 'notch' all the international amateur bands from 1. 8 - 28 MHz and that some DS2-based devices may be set for additional 'notching' around 27MHz to reduce interference to C13. It also appears that the experimental 5MHz amateur allocation and the HF broadcast bands are not general ly 'notched'. This programmable 'notching' allows the choice of what to 'notch' and what not to 'notch' to be made by manufactures of DS2-based powerline adaptors, which seems like a worrying trend for radio users. David Lauder. RSGB. RSGB
Radcom
Magazine
Link:
UKQRM Yahoo Group: http://tech.groups.yahoo.com/group/UKQRM
DONATE on-line to the RSGB Spectrum Defence Fund at www.rsgb.org/defencefund/ Testing Home Powerline Networking Products And Other RSGB EMC Committee Activities Meeting With BT VISION At the BT AGM, a question on the EMC performance of BT Vision products was raised by a BT shareholder who is an expert in EMC. BT management offered a meeting to the shareholder to explore the issues and agreed that the shareholder could include other interested parties in the meeting. The group that met the senior managers of the BT Vision section included Jonathan Stott, representing international broadcasting and general short wave listening interests and Angus Annan, MM1CCR, for the RSG B and Amateur Radio concerns. The original BT AGM question had made the point that BT's corporate guidelines were not being followed in their procurement processes (`goods shall comply with relevant EMC standards`). In particular, the powerline networking devices used for BT Vision were within the scope of the EN55022 standard but did not appear to be compliant with that standard. The meeting was led by the BT sha reholder who outl i ned the i m pact on the H F spectrum that the use of i nhouse PLT for BT Vision would cause and his concerns about waste of BT resources, high field engineer costs and possible unfavourable PR in dealing with interference problems. It was also pointed out to BT Vision managers that the domestic TV licence put the onus on the householder not to cause interference (`You must not let your TV equipment cause undue , interference to radio or TV reception"). Thus, it could be argued, powerline networking adaptors marketed as part of a system for home TV distribution might be seen as causing the customer to be in contravention of the TV licence conditions. Under the Communications Act of 2003, Ofcom has specific powers to enforce this licence condition. Angus Annan spoke about the particular threat to amateur radio as an activity that was concerned with weak and distant signals and also that the Amateur Radio Service was not just a hobby, but is recogn ised by the Cabi net Office as a component of U K emergency services. He pressed the point that PLT can only be an interim technology and that other solutions will be needed to meet the bandwidth req u i rements of H DTV. BT shou ld be developing an approach based on Wi-Fi alternatives such as variants of the I EEE 802.11 standard in the 5GI-1z licence exempt band. There is also the evolving 1394 Trade Association that is developing the Wireless Home Digital Interface (WHD1) that includes remote controls and this is supported by leading manufacturers such as Hitachi, Sharp and Sony. For BT Vision, the Director of Technology acknowledged that Wi-Fi would be the ultimate solution for linking TV sets and other domestic devices but felt that the standards work here was still not at the point where commercial use could begin. On the compliance issues, it was said that BT had adhered closely to their internal project management standard, but the radio interests present pointed out that this was rather avoiding the point. The question was whether BT Vision products were compliant with the relevant European EMC standards. As to what BT should do next, the radio group felt that PLT products should not be offered at all. Wire line had proven perfectly satisfactory for telephone extensions or BT could provide an upgrade to wireless LAN as with other BT offers. Powerline Networking Adaptors Tested  Two members have loaned their
home powerline networking adaptors to the RSG B EMC Committee for
testing. A conducted emission test was performed from 150kHz - 30MHz
using a standard Line Impedance Stabilisation Network (LISN) and an EMC
analyser. Photo 1 shows the equipment on test. This is a pre-com pi ia
nce' test, not a full compliance test as it was performed with
pre-compliance test equipment and was not performed in a shielded
enclosure with a ground plane. Hence the results should not be taken as
indicating whether the equipment on test does or does not comply with a
particular EMC standard. Nevertheless, pre-compliance testing can
provide a useful indication of, whether or not a piece of equipment
would be likely to meet a particular standard if subjected to full
compliance testing. Two types of powerline networking adaptor were
tested. The first was a
Solwise brand that is designed to the'HomePlug Turbo'specification and
supports a'raw'data rate of up to 85 M bps. The second type is a
Comtrend Powerline Ethernet Adaptor with Filter that is supplied for BT
Vision installations (see Photo 2).The test results of the Solwise devices were as si m i la r to the resu Its for a nother Homeplug Turbo product that was tested in 2006 and the results were submitted to Ofcom. As explained in August 2008 EMC, these devices use a frequency range 4.49MHz - 20.7MHz with 'notches'for the 7, 10, 14 and 18M Hz amateur bands. The 'H omepi ug' devices only transmit when they have some data to send but the peak level of such transmissions outside the ,notches' a ppea rs to be well above the EN55022 limit.  The test results for a pair of
Comtrend device are shown in the diagram. This trace was produced using 9kHz measurement bandwidth and a peak responding detector. The EN55022 Class B average and Quasipeak (QP) limit lines are shown for comparison, although the peak detector typically gives results that are a couple of dB above a QP detector. The emissions from a single device would be slightly lower compared to the pair that was tested. It can be seen that the f req uency ra inge occu pied is a pproxi mately 2.2 MHz 28M Hz with notches'for the 3.5, 7, 10, 18, 2 1 a nd 24MHz amateur bands but not the experimental 5MHz allocation.  There is no notch i ng for short wave broadcasti ing a nd other HF radio users such as CB and some cordless mice and keyboards that operate around 27MHz. The Comtrend devices are not designed to the HomePlug specification and the amount of RF emitted appears to be much the same whether they are idle or data is being sent. The envelope of the emission is pulse-modulated at just over 1 kHz, which gives these devices a characteristic sound on an AM receiver. This diagram shows the demodulated output at 5MHz in the time domain with a linear amplitude scale. Although it seems unlikely that such devices would meet the EN55022 conducted emission limits, it is possible to CE mark such devices using the Technical Construction File (TCF) route. It is also possible to challenge the validity of such a TCF, which is what the RSGB did with another powerline networking product in May 2006. We are still waiting for a response from Ofcom. EMC UK 2008 EMC UK is an annual event for professional engineers at Newbury. It is organised by The EMC Joumal and is supported by the Institution of Engineering and Technology (IET) and several other large organisations. It follows the usual arrangement of a trade show and a parallel conference whose delegates circulate round the stands between sessions. For EMC UK 2008 on 14/15 October, the RSGB EMC Committee was invited to provide a demonstration and poster display as part of the IET stand. Our theme was EMC from the point of view of radio users and, more particularly, the radio amateur. The demonstration included posters on modelling emissions from house wiring, the need to protect the H F radio spectrum, emissions from Powerline devices including notching for the amateur bands and the potential problems of dynamic notching to protect broadcast reception (ETS1 TS 102 578 - see Websearch). Three com puter power su pply u in its with a 11 ma i ns RF interference components missing, as featured in April 2008 EMC, were also displayed on the stand with the covers removed. These attracted a lot of attention and most visitors expressed surprise that EMC enforcement activity in the UK is not more effective. The event was a great success. Many of the delegates and staff manning the professional trade stands were interested in seeing the practical effects of noncompliance. A surprising number of the visitors were aware of amateur radio and the activities of the RSG13. Informal discussions with delegates provided useful information to help with the Society's activities related to PLT and TV interference emission standards. Stricter EMC Enforcement? There is a new draft Regulation of the European Parliament and of the Council European that requires member states to have in place a Warket Surveillance activity that is open to public information` by 1 January 2010. This is document 2007/0029 (COD) LEX 901, which can be found on the Europa website (see Websearch). The RSG13 EMC Committee has asked an expert on EMC regulation to study this document. Our expert's opinion is that European Member States will need to have adequate market surveillance authorities who must be empowered and resourced by the State to do their jobs. That might be a bit of a blow to the U K Government who has not given adequate resources to local authorities'Trading Standards departments nor to Ofcom for EMC or RTTE market surveillance. It may well allow Ofcom to bring added pressure on the UK Department for Business, Enterprise and Regulatory Reform (BERR) in their efforts to divest themselves of their duty to enforce the EMC Regulations for the protection of the radio spectrum. In contrast, the German authorities are already well set up for this market surveillance. Making the information on market surveillance public will help to put pressure on Member Sates who don't do much at the moment. Another requirement of these draft regulations is the creation of a scheme of accreditation of assessment bodies. Although this might be regarded by some as another layer of bureaucracy, if it works it should at least help to sweep up some doubtful Notified Bodies and test houses in some parts of the EU that happily provide favourable reports for products that should not be on the market! One issue that the draft regulations do not address is closing an apparent loophole in the EMC Regulations relating to the Technical Construction File (TCF) route for demonstrating product compliance. The TCF route has been used (and some would say misused) in order to CE mark some home powerline networking products. David Lauder. RSGB. RSGB Radcom Magazine DONATE on-line to the RSGB Spectrum Defence Fund at www.rsgb.org/defencefund/ Access BPL can seriously interfere with safety of aircraft flights Access
BPL can seriously interfere with safety of
flight Before the Federal Communications Commission,
Washington, DC 20554, In the Matter of Carrier
Current Systems, including Broadband over
Power Line Systems, ET Docket No. 03-104 Amendment of
Part 15 regarding new requirements and measurement
guidelines for Access Broadband over Power Line
Systems, ET Docket No. 04-37
Reply Comments of Aeronautical Radio, Inc. Aeronautical Radio, Inc. (“ARINC”) hereby submits its Reply Comments in these proceedings. The record makes clear that access broadband over power line service (“Access BPL”) can seriously interfere with the nation’s high frequency communications system that guards the safety of flight and thus should be authorized only under conditions that protect the HF Aeronautical Mobile (R) Service. From: http://gullfoss2.fcc.gov/prod/ecfs/retrieve.cgi?native_or_pdf=pdf&id_document=6516214698 Also see: http://gullfoss2.fcc.gov/prod/ecfs/ retrieve.cgi?native_or_pdf=pdf&id_ document=6516214700 http://gullfoss2.fcc.gov/prod/ecfs/retrieve.cgi?native_or_pdf=pdf&id_document=6516214699 http://gullfoss2.fcc.gov/prod/ecfs/retrieve.cgi?native_or_pdf=pdf&id_document=6516214701 EMC Links
EMC UK EMC Exhibition and Conference: www.emcuk.co.uk European Telecommunications Standards Institute (ETSI), PowerLine Telecommunications (PLT); Coexistence between PLT Modems and Short Wave Radio broadcasting services: http://webapp.etsi.org/action/PU/20080805/ts_102578v010201p.pdf Regulation of the European Parliament and of the Council 2007/0029 (COD) LEX 901: http://ec.europa.eu/enterprise/newapproach/pdf/regulation_en.pdf RSGB Radcom Magazine DONATE on-line to the RSGB Spectrum Defence Fund at www.rsgb.org/defencefund/  http://www.mikeandsniffy.co.uk/UKQRM/
DONATE on-line to the RSGB Spectrum Defence Fund at www.rsgb.org/defencefund/
BPL :
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