Incoming, forwarded for info

Richard Barth
Thu, 25 Feb 1999 13:38:05 +0100

>The Death of HF Radio Operation? 
>Opinion Column 
>Ed Mitchell, KF7VY, <>
>Amateur Radio has long dealt with challenges to HF operation including
>restrictions on antennas and poorly built consumer electronics that are
>highly susceptible to nearby radio signals. 
>A new, and very challenging threat has emerged in the form of home computer
>networks - in particular both home computer and home entertainment
>distribution systems that use unshielded, "twisted pair" copper wiring or AC
>line wiring inside homes to transmit high speed data signals. Incredibly,
>these systems rely on signals in the 2 Mhz to 30 MHz range[1] running over
>unshielded wiring. These systems generate broadband radio frequency
>interference and are highly susceptible to interference from legitimate HF
>radio transmissions. In just 2 to 3 years, the odds are that every other
>house in your neighborhood may be using one of these HF-based network
>Hams have long dealth with interference to and from consumer devices - but
>in the past, the problem was typically due to fundamental signal overload
>problems and the inability of consumer electronics to tolerate nearby radio
>signals of any type. A variety of techniques have been developed to address
>traditional interference problems ranging from the use of high pass filters,
>RFI chokes and ferrite beads, shielded cabling and a variety of other simple
>The computer network inteference problem cannot be solved through the
>installation of a simple filters. In fact, it may not be solvable at all
>since these devices are operating directly within the HF radio spectrum and
>are using unshielded wiring for their links. 
>The Demand for HomeNetworks
>There is genuine demand for home computer network solutions. According to an
>article in Cnet News [2], an estimated 54% of U.S. homes will have multiple
>computers as of the year 2001. Because most homes are not configured for
>network cabling, the networking industry has adopted a mantra of "No New
>Wires" to emphasize solutions that use existing household AC wiring,
>telephone wiring, or Part 15 unlicensed wireless data systems. 
>Telephone Wiring-based Home Networks
>A leading home network technology uses existing home telephone wiring to do
>double duty with both voice and data signals. Voice signals occupy the
>spectrum lower than 4 khz. ISDN and xDSL services occupy spectrum
>(typically) between 25 khz and 1.1 Mhz. In order for home phone networking
>to co-exist with existing functions, home phone networking occupies
>frequencies above 2 Mhz. One product that is available now is called
>HomeRun, from Tut Systems. This product provides a 1 Mbps data rate by
>modulating a data signal between 5.5 MHz and 9.5 MHz with a carrier
>frequency at about 7.5 Mhz. This spans the popular 7 Mhz Amateur Radio
>allocation. Tests that I conducted last year demonstrated that low power 7
>MHz RF signals causes massive packet loss in the data network. Tests showed
>some susceptibility to other sources of RF over a broad frequency range;
>however, the only severe source was transmission on 7 Mhz. This technology
>also generates weak, broadband noise across the spectrum, consistent with a
>device operating as a Part 15 unintentional emitter. 
>HomeRun is a first generation product. The technology is evolving rapidly to
>deliver much higher data rates - 10 Mbps later in 1999, and still faster
>later on. In mid-February, a 10 Mbps standard was formerly proposed to the
>Home Phone Networking Alliance. To provide higher speeds, the technology
>will expand its spectrum usage to the entire bandwidth of 2 to 30 Mhz.
>Because this technology is operating over unshielded copper wiring, and
>based on my tests conducted in 1998, it appears likely that Amateur
>transmissions will greatly interfere with home phone networking, possibly
>over a very wide area due to susceptibility to signals on the same
>Worse, home phone networking will not be confined to computer data
>applications, which due to their packet and error correcting protocols, can
>accommodate intermittent interference. The long term direction of home phone
>networking is the routing of home digital video signals, digital audio and
>other entertainment signals. Data loss in these streaming data applications
>will be extremely apparent to the user of the network. Examples include
>routing a digital TV, digital satellite, or DVD signal to one or more
>displays located in a home. Data rates will be pushed ever higher in order
>to accommodate future High Definition TV signals (which require about 19
>Mbps data rates). 
>Several companies are working together on home phone networking technology.
>Tut Systems received financing from many sources including AT&T and
>Microsoft. Compaq, Intel, and Diamond Multimedia have licensed the
>technology. Another company, Epigram, expects to ship 10 Mbps technology
>chipsets in the first quarter of 1999. 
>AC Power Line Networking
>Another technology sends signals over AC power wiring inside the residence.
>One company, Phonex, sells a telephone extension system that can be used to
>locate a wired phone, modem, or cable TV/satellite TV "set top box" phone
>connection - to any location inside the home. Current products modulate the
>signal on 3.520 Mhz using a FM subcarrier. TCI cable company distributed
>many of these products to users of their set-top-boxes and digital cable
>converters. The DISH Network satellite network also sells these units at
>their web site. The ARRL recently brokered a deal with TCI such that TCI has
>agreed to replace the 3.52 MHz units with new units that operate at a
>different radio frequency, to eliminate interference potential between
>Amateur operations in the 3.5 to 4.0 Mhz band. Still, several million of
>these units are in operation today and are not covered by the TCI
>replacement program. 
>I recently tested a Phonex 3.520 Mhz unit and was surprised at the level of
>RF noise it leaks, especially considering that this is a "wired product" not
>a wireless product. Worse, its basically broadcasting the users wired
>telephone conversations on HF! The signal not only emits from the wiring of
>the house where it is used, but it also leaks back into the AC utility grid.
>Using a handheld shortwave receiver, I picked up S9 signals when near the
>power line, a block away from the home unit. I did not pursue the signal any
>further than that but it seemed likely that the power line would still be
>radiating the signal at two blocks from the home. 
>Not only does the Phonex product leak outwards, but also it is susceptible
>to Amateur transmissions in the 3.5 Mhz band. 
>Phonex is an example of a class of products that use electrical power lines
>for signals. Other products are coming to market that deliver data over
>household wiring in a similar fashion. One product from Intellon, operates
>at 1 Mbps and they (and other manufacturers) claim they will eventually
>achieve 10 Mbps performance. Present systems modulate their signals well
>below any Amateur HF bands; however, it is unknown where their 10+ Mbps
>products will operate. It is likely that these will generate signals well
>into the HF spectrum. At this point, it is unknown if power line technology
>will become a success. The power line networking industry is fragmented and
>has not yet formed an industry trade group, as was done by the home phone
>networking companies. Never the less, Intellon has licensed its power line
>technology to Microsoft Corporation for use in future products. 
>HF Spectrum Filling with Digital Noise Makers
>As described in Part 1 and Part 2 of "The Great Broadband Internet Hoax"
>series, two-way cable modems are using the 5 to 40 Mhz bandwidth for
>upstream cable modem signaling. How bad will this leakage be? I just
>finished a several mile walk around my neighborhood and found television
>carrier leakage from the cable system; fortunately, none of it was within
>the Amateur radio bands. With two-way cable uplinks in the HF band we are
>likely to have leakage on top of existing Amateur HF allocations. 
>A problem that may further compound this situation is that home phone
>networking and cable modems are being routed through existing, internal home
>wiring systems, the quality of which is often quite poor (in other words,
>the "twisted pair" may not even be twisted). When my mother-in-law had a
>cable modem service installed, the cable company had to replace all of the
>internal wiring to get the system to work properly. 
>The 2 to 30 Mhz spectrum is rapidly filling with digital noisemakers. Not
>only do these systems emit RF noise but they are very susceptible to
>interference from clean and legal Amateur radio transmissions. There is no
>simple filtering arrangement to eliminate the interference to Amateur radio
>or from Amateur radio to home networks. 
>Home network products promise significant challenges to future Amateur HF
>operation in residential areas. With estimates that 54% of homes will have
>multiple PCs by 2001, and that networking such systems is a high priority,
>it is a guarantee that Amateur radio operators will be in close proximity to
>these noisemakers and HF operation will become a significant source of
>interference to home networks. Specifically, for the 75% of the U.S.
>population that lives in urban areas, nearly all in-home phone network users
>will be in range of Amateur HF transmitters capable of causing interference.
>Major companies are backing these phone and AC line technologies: AT&T,
>Intel, Microsoft, Compaq, TCI and many others. Therefore, it is likely that
>these products will become widely available and used by millions of home
>computer owners. 
>Where Does This Leave Amateur Radio?
>Legally, Amateur radio operators have Federal communications law on their
>side. Home networking equipment operates under Part 15 rules and must put up
>with any interference it receives from licensed radio services.
>Realistically, while the law is on the side of Amateur radio, home network
>and Internet users vastly outnumber Amateur radio operators. The politics of
>the situation do not favor Amateur radio operation on the HF bands, as we
>know it today. 
>Oddly, the ARRL continues to promote an incentive licensing scheme that puts
>all of the incentives in the HF bands (4 out of 5 the existing license
>classes s are HF-centric). The ARRL is currently conducting technical tests
>near 5 MHz for the purpose of potentially requesting additional HF radio
>spectrum for Amateur Radio, and in the recent license restructuring
>proposals, the ARRL strongly supported retention of telegraphy proficiency
>(historically used most extensively at HF) requirement in the Amateur
>service. While these are admirable goals, the reality of the world we live
>in today is that HF operation is rapidly becoming impossible for most
>Americans in a world filled with antenna prohibitions on all new housing and
>where homes will soon be filled with home networks operating in the 2-30 MHz
>HF spectrum. Literally, Amateur Radio is potentially off limits to most
>Americans. Is it any wonder our numbers are decreasing? 
>Our Amateur Radio "product" is significantly out of step with the real
>world, which may explain why the ARRL recently reported the loss of 14,000
>members, and the overall U.S. Amateur population declined in 1998 by 1,090
>individuals. Worse, with nearly 1 in 3 Amateurs over the age of 65[3], and
>very few Amateurs under the age of 40, these numbers may indicate that the
>Amateur Radio service is literally dying. A few years back, slow Amateur
>radio service growth was based on poor HF radio propagation due to the
>bottom of solar sunspot cycle. With the sunspots now doing their thing, that
>theory is largely moot. 
>In my humble opinion, a hobby radio service that is declining in numbers may
>be in an extremely difficult position to defend its HF operations in the
>presence of vastly more home computer and digital entertainment consumers.
>There is a fair amount of evidence that our Amateur radio "product" needs a
>wholesale rethinking and a major new vision for the 21st century. I have
>suggested ideas for new directions in past Opinion columns, and I won't
>repeat them here. The bottom line is that the ARRL[4] needs to exert a
>strong vision of a "new" Amateur Radio service for the 21st century,
>consistent with the new world that we live in. What can you do? You need to
>communicate your thoughts on these issues directly to your ARRL Director. 
>[1] "The Home Phoneline Networking Alliance", white paper,
>[2] "Tut Systems soars after IPO",
>[3] February 1997 QST reviewed a survey of ARRL members. This data point is
>from that survey and may not be indicative of the overall Amateur
>[4] In both written (see <>) and verbal comments made
>to amateurs, the FCC has stated clearly that it primarily accepts input on
>Amateur radio matters from the ARRL or the QCWA and generally does not act
>on specific proposal from other entities. 
Richard Barth, W3HWN
  Director, Office of Radio Frequency Management
         U.S. Department of Commerce/NOAA
 Temporarily at: Hotel Carlton, Geneva Switzerland
Phone: +011 41 22 908-6850 Fax: +011 41 22 908-6868