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 technologies.

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 solutions.

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

Telephone Wiring-based Home Networks

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 frequencies.

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

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

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?

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 21^st 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 21^st 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, http://www.homepna.org

[2] "Tut Systems soars after IPO", http://www.news.com/News/Item/0,4,31584,00.html

[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 population.

[4] In both written (see http://www.nocode.org) 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.