Letter to the editor in the April 15, 1987, Radio World:
I’ve heard all the garbage I can stand about the AM stereo “issue.” The problem?
1. Motorola and Kahn each was a monopoly.
2. The stations don’t want to waste $6,000 on the wrong system.
3. The FCC is afraid it will be sued by the “sore loser” in a standard decision.
4. The receiver makers are afraid of wasting millions of the wrong system.
5. The listeners don’t know anything about AM stereo.
Does any of this sound vaguely familiar regarding some AM “improvement” schemes currently being used? Those that fail to learn from history are destined to repeat it, Bob.
Oh, if only it were so, AM stations would be rich! Rich, I tell you. This dates back to a 1987 article in radio world that details how AM stations receiving Cuban interference could submit to the USIA (US Information Agency), the State Department VOA oversight organization, detailed interference reports and requests for reimbursement of lost revenue. In addition to that, the FCC would consider nighttime power increases and or pattern modifications, so long as no US or Canadian station was adversely affected by the changes.
Prior to about 1980 or so, Cuba adhered to the NARBA of 1950. This allocated broadcast channels in the AM band, including clear channels for the US, Canada, Mexico, Cuba, and the Bahamas. Later on, most of the countries in South America joined the treaty and most international interference was mitigated.
Then, for reasons only known to Fidel, Cuba began broadcasting high power on several frequencies. The stations suffering the worst interference were all in Florida; WINZ, Miami, WVCG, Coral Gables, WNWS, South Miami, WEAT, West Palm Beach, WQBA, Miami, WKAT Miami Beach and WSUN, St. Petersburg.
In our neck of the woods, WICC suffered some pretty bad interference from CMKA on 600 kHz. According to the treaty, CMKA was supposed to transmit with no greater than 2.5 KW. Sometime in early 1981, they increased power to 150 KW. The path between WICC and CMKA’s transmitter site is almost entirely over salt water. Additionally, CMKA utilizes a fairly tall tower, 130 degrees according to the FCC database.
The interference was worst in the last fall and early spring. Several local newspaper articles were written about the subject, noting that WICC developed a contest around the interference. The station would drop its carrier for 10 seconds at 6:30 and 7:10 pm. Listeners would then try to identify the Cuban songs playing on CMKA and drop a postcard to WICC with that information. Winners were picked randomly from all the correct answers received (CMKA would also be heard on the studio air monitor). Coincidentally, after several months of this, the Cuban station switched its programming to English.
In any case, I believe the USIA paid out a total of $500 K to the Florida stations.
One of the AM stations around here that I am familiar with is considering a downgrade, which is to say reduce power and get rid of a directional antenna system in favor of a non-DA antenna. In this particular case, it makes sense, as the station can co-locate with another AM that is closer to the COL by a good distance. The coverage from the new site at reduced power looks to be a good fit. If this can be arraigned, the AM station in question would lose a multi-tower AM antenna system that is 50 years old and all the attendant headaches, expenses, and labor that goes with it.
Many AM stations that are DA-2 or even DA should consider downgrading to a lower power level and getting rid of their DA system. Directional antenna systems on AM stations are maintenance nightmares. Unfortunately, in the ’50s, 60s, and 70s, it was often thought that adding power, and extra towers to an AM station would give them great swaths of extra coverage. Sometimes it worked out, sometimes it did not. Often what happened was some area was added, but in areas that were nulls toward protected stations, signal strengths went down. What the station ended up with was more towers, more maintenance, monitor points, a sample system, and more expense.
Taking an AM station in the other direction might actually make more sense. Go back to one tower non-directional 1 KW or whatever power can be used in the daytime. Time was when the FCC would only allow certain power levels; .5, 1, 5, 10, and 50 KW. Those were what a new station had to work with. No longer is that the case, any power level can be used so long as it meets interference contours and the city of license contour coverage requirements.
Presunrise authority is normally 500 watts and is available at 6 am, post-sunset authority varies but often a PSA extends the on-air time to 9 pm in the wintertime. For a local radio station, which is what all but the class A AM stations are destined to become, this will be adequate. For a losing station, it may be that, or turn in the license and sell the land to a developer.
Diplexing on another AM station’s tower closer to town is also a good way to get out of maintaining an expensive antenna array with diminishing income.
I was digging through some old manuals at the shop today and I found this June 1987 memo from Orban to AM stations titled “AM radio CAN sound almost like FM.”
The main purpose of the memo was to get AM radio stations to implement the NRSC standard for pre-emphasis and high-frequency roll-off to improve the sound of AM broadcasts on ordinary radios.
I am not sure why the receiver manufacturers never designed an IF filter that would be compatible with NRSC, it seems like a fairly simple design. Instead, what we have is “digital” AM radio (IBOC) which does not work well, and creates many more problems with interference than pre-NRSC broadcasting.
If one were to look at the entirety of AM broadcasting history, one would find some striking parallels with what is happening with IBOC today on both AM and FM.
To start, the NAB began petitioning the FCC to allow more AM broadcasting stations, even as it was known that these stations would create interference with existing stations, especially at night. Still, the NAB persisted and the FCC relented and through the fifties, sixties, seventies, and eighties many more class II and III stations were established on what used to be clear channels (classes I and IA).
Once the AM band was chock full of stuff, they began going to work on the FM band with 80-90 drop-ins.
You see, for the NAB, more radio stations means more dues money, and greater lobbying power because of the larger size of the industry. Then came the deregulation of ownership limits. By this time, Big Group Radio was calling the shots and they wanted more. This led to the great consolidation rush of the late 1990s from which the radio industry is still reeling. The consolidation rush led to highly overpriced radio stations being leveraged to the absolute maximum, leading to recent bankruptcies.
Finally, the NAB’s great push toward adopting IBOC digital radio in the early years of the 00s. IBOC was supposed to save the day, greatly improving the quality of both AM and FM and bringing radio into the 21st century. Except that the promised technical advances never materialized. IBOC remains a great expensive boondoggle and I am beginning to think that perhaps we should stop listening to the NAB.
The memo itself is a fascinating thing, which was one could substitute AM with RADIO and come to some of the very same conclusions today regarding analog and IBOC digital radio. For example, this paragraph on AM stereo:
AM stereo was thought to be an answer (to improve AM), but AM stereo was embraced with the false assumption that having ‘stereo’ automatically meant having ‘high fidelity’. While AM stereo did provide somewhat better fidelity, it was not comprehensively engineered to get the best fidelity from AM. It was hoped that the gimmick of having two channels would be enough to save AM.
AM stereo could have been an improvement, had it been properly implemented. Unfortunately, the underlying problem of bad-sounding receivers was never addressed. About which, the same memo notes:
Receiver manufactures did what they could to reduce listener complaints – – they narrowed the bandwidth (thereby reducing audio fidelity) until the complaints about interference stopped. Listeners clearly indicated, through their buying habits, a clear preference for lower fidelity over continuous irritating static, buzzes, whistles, and “monkey chatter’ from adjacent stations. People accepted this situation for a long time – – until the simultaneous advent of improved receiver technology and the FCC’s anti-simulcasting rules created the FM boom of the late 1970’s. (ed note: I remember listening to FM because there were fewer commercials, not better sounding audio)
Then the memo goes on to stress the importance of implementing NRSC standard for AM broadcasting that included the sharp frequency roll-off at 10 kHz, noting that receiver manufacturers would design “fine new receivers” that would take full advantage of the new standard, but only if broadcasters first showed good faith by widely and promptly implementing it.
As I recall, NRSC-1 was adopted as a rule of law by the FCC in 1989, about two years after this memo was written. One could reasonably expect that receiver manufacturers then started producing radios that took advantage of the NRSC pre-emphasis curve with IF filters that did not cut off audio frequencies above 3.5 kHz, but rather rolled them off in a gentle slope until about 7 kHz, more aggressively after that until 10 kHz, where they cut off.
Except they didn’t.
Instead, twenty years later, AM radios universally sound bad, with an audio bandwidth of about 3 kHz or so.
I believe that AM receivers could be made with three IF bandwidths, automatically selected based on signal strength. Within the 5 mv contour, full (10 kHz) audio can be reproduced using a high-frequency roll-off described above. In the 1 – 5 mv contour, a 6 kHz bandwidth and less than 1 mv a 3 kHz bandwidth. The automatic selection could be defeated with a “wide/narrow” IF bandwidth selection switch like the GE super radios have. Of course, if one were listening to stations transmitting AM IBOC, the “narrow” setting would be the best.
Half of me thinks that the ship has already sailed on AM broadcasting. The stations on the air will continue to decline until they are no longer able to broadcast due to expensive repairs or replacement, at which time they will be turned off. The other half thinks that AM radio, as evidenced by the huge public response to WEOK and WALL broadcasting the true oldies channel, can be revived. With the impending inevitable FM IBOC power increases, translator shoe-ins, LPFM, etc; the FM band may become worse than the AM band. At this point, the public will have to decide whether free radio is important to them, or 3G/4G services will become the new method of broadcasting.
