“FIXING” AM RADIO BROADCASTING – Part 3 of the Future of Radio and TV
Before we can deal in a general way in future posts with the restructuring of radio broadcasting to ensure its survival, there is an even more-pressing radio problem which must be solved. From an engineering viewpoint, as it is currently practiced AM band broadcast radio has no future. It’s now no longer competitive with other consumer-based entertainment modes, and its forthcoming survivability looks even bleaker. In the Curmudgeon’s view its “wireless technology” has to be “fixed” in order for it to survive, and that’s something which is long overdue. The Curmudgeon has dealt with other aspects of the broadcasting conundrum in Part 1 and Part 2.
This post consists of a Curmudgeon proposal outline for doing the AM radio engineering upgrade. This proposal is only one entry in a galaxy of different ways that current AM broadcasting could be restructured for improved survivability. This proposal is, admittedly, radical: “In order to save the patient, we must kill him!” Implementing it would require time, money, dislocations, and new ways of doing things. This is not a “just patch the flat tire and push the car back onto the road” proposal. Rather it is a “jack up the car’s nameplate and roll a state-of-the-art killer road machine underneath it.”
This proposal is centrally dependent upon FCC and other Federal government action in support of the changes and reforms. All the regulatory tools needed to implement it exist within the FCC’s current set of authorizations and its authority. The proposal may also require some one-time funding from the US Congress to aid in the transitions. The fact that it depends upon Federal leadership and support does not auger well for the prospects for its successful implementation. But “doing nothing” is hardly a formula for future success, either!
So, remembering that this proposal is concerned with only the transmission technology side of the medium, and that radio programming and audience retention problems will be the subject of later posts, here it is:
I. The present transmission format is obsolete, beset with problems, and cannot be repaired.
A. The present format (medium wave [MW] frequency band, amplitude (“envelope”) modulation, and 10 kHz channel bandwidth) is an historical artifact. The current transmission standard is still is dictated by the conditions existing at the birth of radio broadcasting. This format is technologically obsolete, and it cannot be “patched” or repaired any longer.
B. Increasing environmental RF noise levels around 1 MHz are demolishing AM broadcasters’ authorized “listener coverage areas,” and the format itself has no inherent radio noise-suppression capabilities. The medium wave band is no longer a desirable location for local area broadcast service.
C. Nighttime ionospheric propagation of MW signals, hugely expanding their daytime coverage areas, makes nationwide frequency coordination almost impossible. The national AM channel coordination problem has not been successfully solved in 90 years.
D. The restricted audio modulation bandwidth makes current AM broadcasting non-competitive for musical programming, a major component of much radio broadcasting. It also severely limits the future provision of new services to the public, such as “digital program” and “digital data.”
E. The tall AM transmitting antenna towers (~150 feet, minimum height) are no longer acceptable to neighboring communities. Zoning approval for any new or relocated towers may be almost impossible to obtain. The land underlying existing towers represents a potential source of available capital for broadcasters.
F. Overall, the present “1912 format” of AM radio broadcasting has reached the end of the road, and no amount of further “patching” can resolve its inherent technological deficiencies.
II. Moving AM broadcasting into the future: a new broadcast band
A. It is therefore proposed that currently-practiced AM broadcasting be scuttled and shut down at some future “date certain” and replaced with a new broadcast radio service designed ab initio for the twenty-first century.
B. The new service would be located at VHF frequencies, would employ digital (only) modulation, and would have assigned channel bandwidth sufficient for multiplexing digital program and data sources.
C. Proposed frequency assignment: TV Channels 5 and 6 (76 – 88 MHz). These channels are presently only lightly used since the Digital TV Transition. The FCC has the authority to “repurpose” the spectrum for this new use. The Federal government could make a loan fund or tax credits available for the relocation costs of the few remaining TV broadcasters on these two channels. Present TV translator and LPTV licensees using these channels would be offered priority in obtaining radio licenses on the new band. Once in operation, the new band would provide contiguous “broadcast radio” from 76 to 108 MHz.
D. Propagation characteristics and transmission equipment designs for the new VHF service are very similar to the existing FM broadcast service. National frequency coordination becomes feasible because the “new VHF band” stations’ geographical coverage areas remain “local” around the clock, except during rare propagation anomalies.
III. A new modulation system and transmission bandwidth
A. Moving radio broadcasting into the future, the new “VHF relocation band” would be established and operated from its beginning as digital-only.
B. An exact digital format is not specified in this proposal. Engineering standards for the new digital transmission format would be developed by an industry/government/IEEE working group. The proposed channel bandwidth would be 200 kHz, to maintain parity with existing FM broadcasters. Transmitted Effective Radiated Power (ERP) levels and minimum received signal strengths would be determined through initial model calculations followed by field testing.
IV. A transition plan: FCC actions
A. The AM broadcasting transition is to be designed and managed by the FCC using the model established for the past Digital TV Transition, as modified by “Lessons Learned.” The plan is to be established at the time that the engineering standards for the new radio band are adopted and final Part 73 Rules released.
B. The FCC will “clear” existing full service TV licensees on Channels 5 and 6 with relocation assignments, will clear international border area TV channel assignments in consultation with neighboring governments, and will establish termination or relocation dates for TV translators and LPTVs currently using these channels.
C. The FCC will establish a revised “all channel radio receiver” requirement, with new consumer receivers designed to receive: the standard (AM) MW broadcasting frequency range (with “sunset” of this requirement after the Transition Date), an expanded VHF receiving range from 76 to 108 MHz, and demodulation of both conventional FM and AM plus the new digital-protocol.
D. The FCC will establish specifications for new external radio broadcast converter devices for connection to existing receivers. These devices would convert “new VHF band digital signals” to either conventional AM or FM broadcast signals for playback through legacy receivers. There could be a possibility for a partial government subsidy to consumers for help in purchasing the converters.
E. The FCC will accept applications from existing AM broadcasters for “second channel” assignments on the new VHF band during the first application window, then will accept applications from current translator and LPTV licensees during the second, and finally from new broadcasters for the remaining channels during the third window.
V. Transition plan: current AM broadcasters
A. AM broadcasters would file for “second channels” on new VHF digital band, and they might also apply for Federal loans for construction of their “second stations.”
B. The broadcasters would engineer and build their second stations to meet Construction Permit deadlines and then begin to operate them in parallel with their existing AM stations.
C. On a (“date certain”) Transition Date broadcasters would cease AM transmissions. Present AM licenses would be cancelled on that date.
D. Post-transition, broadcasters could consider sale of existing AM transmitter plant real estate holdings to repay construction loans
VI. Transition plan: current FM broadcasters
A. The FCC would determine a second (later) mandatory transition date deadline for existing FM broadcasters to convert, on their existing channels, from the present FM transmission mode to the new digital transmission mode. This would occur after the AM transition to VHF has been completed.
B. The transition from FM to digital transmission could be as simple as change-out of existing (transmitter) exciter decks. The new transmitted ERP authorization for the former FM broadcasters would be that of the already-transitioned AM stations. No frequency changes are involved.
VII. Transition plan: Medium wave AM band.
A. The Medium Wave AM band could be repurposed after broadcast stations cease its use.
B. One suggested use for the newly-available band: one-way wide-area Public Safety dispatch and emergency back-up communications, for carrying digital data, limited video, and graphics to their field operational units. This could be part of a “nationwide First Responder network.” Broadband channels could be established for this purpose. Other usage proposals are solicited.
VIII. Summary
And when it is all completed, where do we then stand? It will have taken much work and expense, and nobody will have received everything that he wanted. But the US will have developed:
A. A single radio broadcast radio service with transmission parity among all broadcasters
B. The salvation of the existing AM broadcasters, as prior to the future transition date many would have “gone dark” because of constantly diminishing earnings in the fading AM broadcast environment. With the transition they will then become competitive.
C. A fully digital radio environment with designed-in flexibility for addition of multiplexed non-broadcast services on the new carriers.
D. A truly “local” radio broadcast service with no “nighttime problem” and with the potential for up to 160 broadcast channels in each major market, all of which would be re-usable elsewhere with standard VHF mileage separations.
E. Removal and mitigation of some ground-based AM transmitter plants and towers.
And it is feasible. We’ve already done the (harder) “digital TV transition” and despite much wailing and gnashing of teeth, during that exercise very few people dropped into huge cracks in the earth never to be seen again! On a difficulty scale of one to ten, with ten representing the almost impossible task of sending men to the moon and returning them safely to earth, this (radio) transition project is a ………….one-half.
This proposal is a starting point for a “new beginning” for historical AM broadcasting. It needs inputs from a wide variety of perspectives. It needs to undergo, and to be improved by, a “clash of ideas.” It and/or its successors need to be moved forward toward a final transition date and the emergence of a new broadcast radio service for the twenty-first century.
Or, we can just sit tight and wait until the utility power feed to the last AM transmitter in the United States is turned off and the last AM carrier drops off the air. And then weakly mumble, “Perhaps we should have done something?”
The floor is completely open for your thoughts, criticisms, and proposals. “Who will make the first bid?”
What do you think?
“Let’s save the universe for RF!”
The old RF Curmudgeon
