Zero Bias: November 2004

Regulation by Bandwidth

Warning! Last month's editorial had me reflecting on hamfest conversations and a day at the beach. Well, vacation's over and it's time to go back to school. This month's topic -- changing the way we organize our frequency bands -- is pretty complicated, but very important. It's an issue that will affect every ham who's active on the air. So, while you might not find this month's "ZB" particularly entertaining, I hope you will find it educational … which means that, yes, actual thinking will be required. You've been warned.

The ARRL’s recent proposal to ask the FCC to shift from regulating subbands by mode to regulating them by maximum signal bandwidth has resulted in quite a bit of discussion, much of it negative – something to be expected when people perceive that their status quo is being threatened. But despite the negatives, and there are some, the League’s proposal is an idea whose time has come.

First and foremost, I want to say that CQ strongly supports the concept of regulating subbands by bandwidth rather than mode (and has for years), especially since new modes like digital voice or MFSK 16 are kind of hybrids (more on that in a minute). Second, we applaud the ARRL for taking on this issue and especially for publicly posting and drawing attention to its draft proposal before submitting it to the FCC. This way, the folks in Newington can get as much input as possible from as many people who may be affected as possible, before the FCC comment process begins. This is good, because the ARRL’s draft, while a good starting point, needs some work to assure that no one group of amateurs benefits or is penalized unfairly by any changes.

Why Bandwidth Regulation?

Some of the new modes in use by hams today, and certainly more of those that will come on the scene in the future, don’t fit neatly into the traditional “mode” definitions. For example, is a digital voice signal “phone” or “data”? Are photos sent by MFSK 16 “image” or “data”? In both cases, the answer determines where it’s legal to operate the modes, and in both cases, as our web guru, K0FO, says, the answers are “clear as mud.”

When I was reviewing the AOR ARD-9800 digital voice modem (see June 2004 issue), I learned that some hams using the 9800 were operating digital voice on 30 meters, a CW/data-only band. Their argument, which is not without merit, is that what they are transmitting on the air – a digital bitstream – is data, not phone. It only becomes a voice signal, they argue, after it is received and processed. Limiting bandwidth on 30 meters to no more than 500 Hz, as the ARRL proposes, would solve that problem – the digital voice signal has a bandwidth of roughly 3 kHz and would clearly be prohibited.

On the other hand, an MFSK 16 signal is about 315 Hz wide, so it would clearly be permitted in a 500-Hz maximum bandwidth band segment, regardless of whether the “message” was text or a photo file. Simple, no? Well, no, not really. Nothing ever is…

The ARRL’s Proposal

The central part of the ARRL’s draft proposal is to replace specific emission modes with maximum signal bandwidths. Band segments currently used primarily for CW communications would have a 200 Hz maximum bandwidth, while those segments commonly used for digital modes would have a 500 Hz maximum. There would also be some band segments where signals as wide as 3 kHz would be permitted. These would be taken mostly from the current Novice/Tech Plus bands that the League has already asked the FCC to “refarm,” plus the top 50 kHz of the current 20-meter CW/data band. This would be to accommodate “wideband” HF digital modes such as Pactor-III, which occupies 2.4 kHz of spectrum space. (Curiously, though, there is no proposal for any 3-kHz data segments on 10 meters, where the CW/data subband alone is wider than most of the other HF ham bands in their entirety.)

The League proposes a footnote for these segments prohibiting phone emissions in these “wideband digital” segments – but that takes us right back to the digital voice question – is it phone or is it data? This footnote reintroduces exactly the type of confusion the proposal is trying to eliminate. A better approach is needed. Likewise, there is no prohibition proposed on using wideband digital modes on the traditional analog phone bands.

Separating Incompatible Modes

One thing that was clear to me when playing with digital voice was that it is not compatible with analog voice – in either direction. A strong DV signal a few hundred Hz away will make a traditional SSB QSO impossible, while a strong SSB station adjacent to a DV QSO will introduce enough “noise” that the signal won’t decode properly. Similarly, Pactor-III and other wideband digital modes will not be compatible with analog SSB. One particular problem with Pactor-III (which is important because it’s the mode used by WinLink 2000, recently adopted by the ARRL as its primary HF digital mode for emergency communications) is that it has a network of automatic and semiautomatic relay stations. Currently, these are restricted to small pieces of the HF bands. Semiautomatic stations (which may transmit only in response to a query from a station under manual control) are permitted elsewhere on the HF bands, but they are limited to 500 Hz bandwidth. The League’s draft would prohibit automatically controlled stations on HF (a problem for what’s left of the HF packet network) but would permit semi-automatic stations throughout the “wideband digital” and phone bands. The only problem with semi-automatic stations is the nature of HF propagation – the person activating the remote transmitter has no way of hearing what the band sounds like at the remote location, so there is the distinct possibility of unintentionally causing interference with a QSO in progress that the human control operator cannot hear. This also sets up the potential -- as these modes become more popular and more numerous -- for significant interference problems between incompatible modes.

It is therefore essential that any change such as the one proposed be accompanied by a strong voluntary band plan, establishing separate areas for incompatible modes. All "major players" must agree to these in advance -- and then abide by them.

In an e-mail to CQ, ARRL Chief Executive Officer Dave Sumner, K1ZZ, agrees in principle, saying that “within the regulatory framework (present or future) there has to be an additional framework of voluntary ‘good practices’ – (such as) band plans.” On the other hand, Dave points out that “the regulatory framework – since it doesn’t change very often or very quickly – has to be sufficiently loose to accommodate things we haven’t even thought of yet.” Dave is 100% correct on both counts, and voluntary band plans have always been an important part of amateur radio’s self-regulatory tradition. However, we would strongly encourage the League to add into its rulemaking proposal a statement that “All amateurs are strongly encouraged to cooperatively develop and abide by voluntary band plans to minimize interference between incompatible modes.”

And Furthermore…

There are a few other points that need attention but that we don’t have space to examine here in detail. For example, the unexplained and inexplicable provision to permit “continuous test transmissions” on all VHF and UHF bands, except for 50-51 MHz and 144.0-144.1 MHz (a recipe for incredible QRM); and the elimination of all bandwidth restrictions (beyond staying in the band) for all bands above 222 MHz, which has the potential for disastrous consequences to EME, satellite and other weak signal communications on the UHF and microwave bands. The VHF/UHF weak-signal and satellite communities need to weigh in with alternatives that will accomplish the worthy goals of encouraging experimentation with new modes while still protecting current activities. Finally, the issue that has bogged down this concept in the past -- how the typical ham measures the bandwidth of his/her transmitted signal -- is dealt with by not being dealt with, except for a comment in an ARRL news release that measurement would not be necessary because the proposed limits "are more than sufficient for 'clean' signals using the traditional HF modes." There needs to be discussion of whether there is general agreement on this point.

Again, we applaud the ARRL for laying out the groundwork on this important issue. Several critics have suggested that because the draft is flawed, it should be scrapped and started over. Throwing out the baby with the bathwater is not the right approach. The purpose of putting the draft out for public comment was to identify the flaws and get suggestions for improvements. We encourage everyone to read the ARRL’s draft (the whole thing, not just the synopsis – both are at <http://www.arrl.org/announce/bandwidth.html>), compare it with the current rules and send comments and suggestions to <bandwidth@arrl.org>.

Happy Thanksgiving!

73, W2VU

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