RFI, CB, and the FCC

Editor's Note: We are reprinting this 38 year-old "As We See It" essay because if you substitute the words "WiFi" and "cellphone" for "Citizen's Band" and "CB Radio," you will realize that not much has changed in the decades since, with our audio systems still awash in a bath of RFI.—John Atkinson

Although Citizen's Band radio may hold little interest for perfectionist audiophiles, there is a good chance that it may intrude upon our activities in some disastrous ways if we, and the audio industry in general, sit back and ignore what has been going on behind the scenes in Washington, DC.

The world of politics is largely beyond the scope of a magazine like The Stereophile and, for that reason, we have never urged our readers to political action before. But when Congress considers an action that could sound the death knell of state-of-the-art audio, then we think it's time for us—and you—to act.

The Federal Communications Commission now receives over 100,000 complaints annually about radio-frequency interference (RFI) in home entertainment equipment. An estimated 87% of the complaints involve Citizens-Band radio operation, both legal and illegal. It's no secret that many CBers operate bootleg rigs with power levels as high as 1000 watts (24dB above the 4W legal limit), and that these are responsible for most interference in audio equipment; but even legal operation can cause severe interference to television reception. This is because harmonics of the 27MHz band used by CB radio occur in several of the VHF TV channels. And FCC standards for CB equipment are unconscionably low.

The sensible way to approach this RFI epidemic would be to crack down on CB violators and tighten the mandatory specs for CB transceivers, requiring a significant amount of harmonic suppression. But the FCC has not, historically, been noted for taking the sensible approach. They want to treat the symptoms instead of the disease. Specifically, they're asking Congress to give them the power to regulate the manufacture of all consumer-electronics equipment—this, of course, would include audio components.

The FCC maintains that, in most cases, it is not the offending transmitter but rather the equipment suffering the interference which is at fault. They say that most home-entertainment devices are susceptible to RFI because they lack adequate filtering (and in view of the way some renegade CBers operate, that's not unlike blaming a murder victim for not having had the foresight to wear a bullet-proof vest!). So, obviously, their solution to the RFI problem is to require the incorporation of filtering components into all electronic devices. But there are two important flaws in this scheme.

First, the FCC's notions about audio are antediluvian. FCC "information bulletins" about RFI have suggested adding bypass capacitors or series inductors to audio circuits to alleviate RFI. Bypass capacitors shunt to ground RF energy which would otherwise reach an active device (be it tube or transistor), where the radio signal could be rectified and hence detected. Series inductors attempt to keep RF out by presenting a higher impedance at radio frequencies than at audio frequencies.

The trouble with these things is that they also affect audio frequencies; bypass caps can shunt a significant amount of energy in the upper treble range, and series inductors can block an appreciable portion of high-frequency audio energy. But even more important than the frequency-vs-amplitude anomalies are the effects on phase and transient response. We won't go into a detailed technical discussion here. Suffice it to say that research going back to the 1940s conclusively links overall amplifier bandwidth with phase and transient response characteristics. Mandatory brute-force filtering of the high end will have an adverse effect on the way audio frequencies are reproduced, and particularly on the way transients are handled. And the importance of transient response need not be stressed again here. Thus, if the FCC can order brute-force filtering in audio circuitry, the art of music reproduction could be set back about three decades.

While Stereophile readers are primarily concerned with audio reproduction, it would be appropriate at this point to examine how CB creates television interference (TVI). We'll start with the "official" version.

The FCC and the CB industry maintain that 90% of all TVI problems are the fault of the TV receivers. They claim that TV sets do not adequately reject out-of-band signals, such as those in the 27MHz band used by CBers. (These are outside the television bands—TV channel 2 begins at 54MHz.) When an out-of-band signal of sufficient amplitude reaches the input of the first stage of the TV tuner, it will overload the stage and generate a series of harmonics; these may or may not be frequencies used for TV service. In the case of the 27MHz band, the second harmonics will be in TV channel 2, the third harmonics for most of the CB channels will be in channel 5 (although a few of the new channels on the 40-channel CB sets will be in TV channel 6), and the seventh harmonics will be in TV channel 9 (footnote 1).

Now that we've heard the "official" version, let's look at the facts. Front-end overload, as described above, can and does occur. But it does not account for a significant number of TVI problems. Only very old sets—or very cheap portables—are susceptible to overload from a CB transmission of legal output power, and then this can only occur if the CB set and the TV are separated by a very short distance.

But legally-powered CB sets can and do emit generous amounts of harmonics, which will be received by any TV set within several hundred feet. These harmonics can cause serious interference to television reception, and this has been a matter of great concern to the broadcasting industry.

When the FCC was considering CB channel expansion last summer, broadcasters filed reams of material to express their opposition. In a Notice of Inquiry in the Federal Register (41 FR 14527-31), the Commission invited public comments not only on channel expansion but also on the possibility of increasing the amount of harmonic suppression required on CB transmitters from 49dB to 70dB. Data submitted by the Association of Maximum Service Telecasters showed that, even if the level of harmonic radiation were held to 4 x 10–7 watts (70dB below the fundamental), severe TVI would still result at distances up to 800 feet at the Grade A contour of the television, and up to 9000 feet (or 1.7 miles) at the Grade B contour.

They concluded that a minimum of 110dB of harmonic suppression at the CB transmitters would be necessary to eliminate most TVI. The CB forces, however, contended that even 70dB worth of filtering would be too expensive, and unblushingly suggested that 60dB would be ample. Amazingly, the FCC concurred and, in a Report and Order on Docket No.20120 (41 FR 32678-83), adopted the 60dB limit on harmonic radiation.

An engineering statement submitted by ABC demolished another of the myths promulgated by the FCC and the CB people—that, while interference to TV channels 2, 5, and 6 may be caused by harmonics from a CB transmitter, interference on any other channel is the fault of the TV set. ABC submitted a report showing that CB installations often emit large amounts of higher-order harmonic energy. One model was found to have a seventh harmonic that was 20dB above the level of the second harmonic, and a fifth harmonic 14dB hotter than the second. This latter is particularly noteworthy, since the frequencies of the fifth harmonics of most CB channels fall in a band of frequencies used for air traffic control communications. Pilots have already reported sporadic interference in ATC from CB installations. If that becomes a more common occurrence, CB could become a real threat to public safety—something to think about if you fly!

Of course, ABC and AMST were not the only broadcasting interests to protest CB expansion. CBS, the National Association of Broadcasters, and several individual stations also objected. But the CB interests carried the day.

Why would the Stereophile dwell at such length on the TVI situation, when it seems to have so little relevance to audiophile interests? To make three very important points:

• 1) Broadcasters opposed CB expansion in spite of the fact that the CB industry, which has been spending money hand-over-fist on TV and radio advertising, wanted expansion very badly; and the broadcasting industry is usually loathe to do anything that may offend paying advertisers. This indicates just how seriously they view the CB interference problem.

• 2) Even with all their clout, the broadcasters were unable to thwart a CB industry goal in proceedings before the FCC. If that agency is given authority over the audio industry, and the CB industry continues to support brute force filtering in amplifiers, what hope will we have?

• 3) The broadcasting industry maintains an army of lobbyists in Washington whose job it is to keep abreast of any bill that has anything to do with communications. They were aware of the existence of bills to give the FCC authority over the manufacture of all consumer electronic equipment, but they made no move to support such legislation. They know what we know—that it is CB operation, both legal and illegal, that causes interference, and not inadequacies in home entertainment equipment.

Of course, even though the broadcasters won't support RFI legislation, it will receive a good deal of support from the CB industry and from CBers. Syndicated newspaper CB columns and CB magazines have already begun urging their readers to write to their Congressmen and Senators in support of such legislation. Although there is little that a small industry like the perfectionist-audio industry can do to offset the effects of the professional CB lobbyists in Washington, we audiophiles can do a lot to balance the effects of CB letter-writing campaigns with letter-writing campaigns of our own.

We urge you to write to your Representative and to one or both of your Senators to express your opposition to FCC regulation of the audio industry, and point out that this is simply an FCC cop-out; if the FCC had used what regulatory authority it already has a little more wisely, the RFI epidemic would never have developed.

It might also be appropriate to point out that, in spite of the good image of CB created in the press by a massive public-relations campaign, all is not sweetness and light on the 11-meter band. The potential for evil is at least as great as the potential for good.

Authorities in Boston charge that CB was used to coordinate attacks on police during anti-busing riots last winter. There are documented cases of "air hogs" refusing to relinquish the emergency channel for bona fide emergency calls, negating the vaunted "life-saving" function of CB radio. In some instances, stranded motorists have been robbed while waiting for help after making emergency calls.

What's more, technical violations are rampant. One CB magazine estimates that as many as 40% of CB hobbyists use illegal linear amplifiers (RF power amps) to boost their transmitting power far beyond the 4W legal limit. Power mikes capable of driving CB rigs into overmodulation are also commonplace. But the FCC does nothing about these and other common infractions.

But we're not alone in seeing the dark side of CB. The consulting firm of Arthur D. Little, Inc., in a study prepared for the White House Office Telecommunications Policy, made some very gloomy predictions about the possible consequences of uncontrolled CB operations, and raised an important question of social policy:

"The first and perhaps most fundamental issue is whether the FCC should allow the existence of a service that it is unable to regulate by virtue of the fact that the size and nature of the service are beyond the reach of practical enforcement measures."

You can find excerpts of this report reprinted in the Congressional Record of September 17, 1976 (pp.E513–-37). It makes very worthwhile reading.

Although legislation to give the FCC authority over the manufacture of audio components died in committee in the 94th Congress, we should not feel at all confident that such nonsense will not become the law of the land during the next two years. The average legislator knows less about electronics than we know about Egyptian hieroglyphics. And he'll be getting a barrage of misinformation about the nature of the RFI problem from both the FCC and the CB people.

The effects of their Blitzkrieg can be offset by letters and personal visits from constituents who are well-informed and articulate (and we are sure most of our readers meet both of these criteria). Do your part! If you don't, and FCC regulation of audio becomes a fact of life, you'll have nobody but yourself to blame.—Jack Hannold

Last-minute addendum: We have just learned, as of March 17, 1977 that the legislation in question has been re-introduced in the Senate by Arizona's Barry Goldwater. If you have any interest in safeguarding the future of high fidelity, now is the time to let your Senator know how you feel about that bill (Number S-864). You could in fact do worse than to send him a copy of this editorial.—J. Gordon Holt

Footnote 1: This is analogous to a phenomenon that sometimes afflicts audio systems. Intense subsonic signals—e.g., record warps intensified by a tonearm-cartridge resonance—can overload a phono preamp. If extremely powerful, they may produce harmonics in the audible range by driving the phono stages into clipping. Even when well below the level where clipping will occur, such signals reduce the distortion-free "headroom" of a circuit by loading it with superfluous energy; what's more, a subsonic can combine with audio frequencies to produce un™ necessary IM distortion.—J. Gordon Holt