An ad-hoc group of engineers is investigating the idea of a complete overhaul of regulation of AM Radio in the United States. AM radio has suffered in recent years for technical reasons in addition to neglect and poor programming. The overall listenability of AM has been hurt by a rising noise level in the medium wave band, poor receivers and transmitting plants in poor condition. The poor condition of transmitting plants is due to the lack of qualified people to fix them, corporate intent and economic limitations derived from poor earnings.
The noise level increase is due to a number of factors including CFL lamps, computers, controllers in virtually all electrical devices in the home and office, LED traffic signals and the poor condition of the electrical grid. This combined with the noisy medium wave environment in modern cars generated by the plethora of automotive microcontrollers whose clock and data signals leak into the AM section of car radios.
What this noise does is decrease the service range of AM stations, and destroy AM service within populated areas. FM stations are less susceptible to noise floor increases because FCC part 15 regulations specify noise specifications at 3 meters from the noise source in the 100 MHz frequency range. You only have a few emitters within 3 meters. In the medium wave band the distance for measurements is Lambda over 2 Pi – as much as a hundred meters. Within a hundred meters of an AM reciver there may be hundreds of unintentional radiators all adding to the ambient noise.
It is extremely unlikely that the regulatory environment with respect to unintentional emitters will change enough to resolve AM broadcasting’s problems, or even if it were to change that the number of installed devices that cause interference would decrease in a reasonable time. (CFL lamps last a long time). The only solution is for AM stations to deliver a higher signal level to the receiver. This can be accomplished in several ways – more power, synchronized networks and moving the transmitter closer to the listener.
Present FCC regulation inhibits this in several ways: The allocation standards were established in a time where the noise floor in the medium wave band was much lower so they are terribly out of date, antenna efficiency standards require the installation of huge transmitting antennas which generally may not be located in populated areas due to zoning, aviation and building code restrictions, and the reticence of the FCC to authorize experimentation with synchronous networks, modified emissions and other experimental improvements to operating AM stations.
Another problem that AM stations have is the variation in coverage from day to night. This has been exacerbated by recent tinkering with Daylight Savings Time. Most AM stations are limited in coverage at night by reduced power, restrictive directional patterns and high levels of interference from other stations. With higher power class B radio stations there has also been problems with “Critical Hours” interference, for which stations other than class A are not protected.
The regulation of AM stations is based upon science that was available more than 50 years ago, and we recognize that much more is known today about propagation than when the regulation were written. Night propagation is much better modeled by the methods developed by John Wang of the FCC and adopted by the ITU.
Licensing requirements for AM stations also are a problem for AM stations. FCC local ownership restrictions count AM stations as equal to FM stations, even though an FM station can have three (and possibly four) programming channels. Daytime AM stations operate only half the time (on an annual average basis) yet they count equal to a full time station. AM stations must provide “city grade” coverage over the entire principal community. This restriction makes it nearly impossible to relocate an AM night transmitting facility.
There will be a series of articles on this site with surveys and draft proposals for various changes to the regulatory environment to assist AM stations in this new competitive and economic environment. Please comment with your opinions and add facts to help AM to rebuild.
Links to proposals: