FCC Authorizes AM radio stations to operate using all-digital broadcast signals

Many thanks to SWLing Post contributor, Paul Evans, Mike S, and a number of others who have contacted me regarding the FCC’s Authorization of All-Digital AM Radio. Below, you’ll find the FCC press release:

For Immediate Release


Action Will Improve Listening Experience and Provide Consumers with Enhanced

WASHINGTON, October 27, 2020—The Federal Communications Commission today
adopted a Report and Order that allows AM radio stations to operate using all-digital broadcast
signals. AM broadcasters will be able to voluntarily choose whether and when to convert to
all-digital operation from their current analog or hybrid analog/digital signals.

All-digital broadcasting offers AM listeners significantly improved audio quality and more
reliable coverage over a wider listenable area than analog or hybrid digital broadcasts. It also
allows broadcasters to provide additional services to the public, such as song title and artist
information. These enhancements will enable AM broadcasters to better compete in today’s
media marketplace.

Today’s Order establishes technical rules to protect existing AM broadcast stations from
interference. In addition, stations converting to all-digital operation will be required to notify
the Commission and the public 30 days in advance of their transition. These stations must
provide at least one free over-the-air digital programming stream that is comparable to or better in audio quality than a standard analog broadcast. They also must continue to participate in the Emergency Alert System. The Order envisions that AM broadcasters will decide whether to convert to all-digital operation based on the conditions in their respective markets.

Action by the Commission October 27, 2020 by Report and Order (FCC 20-154). Chairman
Pai, Commissioners O’Rielly, Carr, Rosenworcel, and Starks approving. Chairman Pai, and
Commissioner Rosenworcel issuing separate statements.

MB Docket Nos. 19-311, 13-249


Also, check out articles at Radio Insight and Radio World regarding this authorization. 

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20 thoughts on “FCC Authorizes AM radio stations to operate using all-digital broadcast signals

  1. Peter L

    I see people arguing that it should have been DRM. Go back to your rooms – ain’t gonna happen. HDRadio works fine. DXers hate it but DXers hate anything new (C-QUAM, anyone?).

    I take this opportunity to remind the assembled masses that MA3, because it has no legacy analog signal, is much narrower than MA1 meaning that ALL the power is in the digital signal now. Listeners with HDRadios which are surely almost all in cars, will be impressed, especially when they realize that AM will have the same dash features (album covers, song titles, etc, etc) as HD on FM or streaming from their phones.

    AM needs all the help it can get and hardly needs hobbyists (I am one) griping that they can no longer hear some far off out of market station now that the local station goes MA3.

    1. Mangosman

      There are 35 DRM transmitters in India whos power is much greater than the most powerful AM transmitters in the USA. The DRM transmitters cover a population double that of the USA. It is the FCC who has not allowed DRM into the USA or even a comparative trial with pure digital HDradio. The USA only has one low powered all digital HDradio transmitter on air and it has an experimental licence until this week.
      The problems with pure Digital HDradio (MA3) are;
      The digital signal power is less than 6 % of the the carrier which is the power specified for the transmitter so the coverage area is much smaller than in AM for the same transmitter. So Peter are you talking of pure digital HDradio in the AM band, or Hybrid HDradio in the AM band or Hybrid HDradio in the FM band?
      There are no pure HDradio transmitters in the FM band on air.
      The data rate is only 20 kbit/s if the signal is a total of 10 kHz wide ie fits within its channel. There is a 20 kHz wide option which gives 40 kbit/s wide signal but this causes the interference referred to to other broadcasters
      The sound compressor gives inferior sound compared to the new xHE-AAC used in DRM at the same bit rate
      DRM has a higher bit rate than pure digital HDradio which can be used for better sound or, pictures, text..
      Pure digital HDradio still uses the carrier which contains no information at all and is a big waste of electricity. In addition the digital signal below the carrier is identical to the digital signal above the carrier but phase inverted. In DRM the whole signal consists of unique signals over the channel allowing better error correction.
      AM radio is 100 years old, HDradio is 20 years old neither are new, it is just that DRM is much better than HDradio.

      Xperi claim 75 % of new cars have HDradio fitted on the production line, but if you look at the total number of claimed receivers and the look at the total number of road licenced vehicles, its about 25 % with HDradio.

      It remains to be seen how many AM broadcasters will switch off AM.

      1. Keith Perron

        Where are the DRM receivers? DRM in India was invested into by All India Radio stations only. And it isn’t exactly a success.

        Radio does not take its ordered from hobbyists.

  2. Zack S

    There are 273,000,000 cars in the US and I bet that 90% of AM listening is done in cars. How many people do you think will replace their car radio to get HD radio? I have never met anyone who put a HD receiver in their car when HD was being promoted in the past. They will probably just say the hell with that and listen on their phone.

  3. Desmond Walsh

    Can anyone tell me the characteristics of DRM transmissions ? Does the power change if there is NO modulation ? So is the power transmitted constant and unrelated to programme content ?
    A comment I would like to make is why was ISB never used for stereo modulation with AM ? Upper and lower sideband would carry left and right-hand channels , and ordinary AM receivers would produce normal mono audio. Modern circuitry could have introduced such a system many years ago , and even carrier reduction ( say 6 to 10dB ) could have been introduced as well .
    I would welcome any observations !
    Des Walsh EI5CD, Cork , Ireland .

    1. Ron F

      DRM transmitted power is constant regardless of modulation. (Something that unskilled DRM proponents overlook is that the measurement criteria differs; AM is typically stated as Peak Envelope Power (PEP), while the continuous power & multiple carriers of OFDM systems like DAB/+/DRM etc necessitates characterisation as some sort of average power measurement.)

      ISB was used for AM stereo, at least in some systems (e.g. Kahn/Hazeltine). In theory, it’s simple enough; in practice it has problems (if interested, read up on Kahn vs C-QUAM) and working around them results in side-effects that limit its attractiveness – e.g. to stay within PEP limits, *average* power (and therefore coverage area, at least in stereo) is reduced; stereo audio bandwidth is even more limited (1/3 of mono) than C-QUAM (1/2 of mono), again to keep within spectral limits; etc.

      Kahn’s work at overcoming the limitations of ISB *did* end up becoming the basis for his coverage-boosting technology (Power-Side), and eventually the basis for the AM-compatible simulcast modes of both HDRadio & DRM, so there is that…

      1. Mangosman

        An AM transmitter power rating is the power radiated when there is no modulation ie silence. (PEP has never been used to power rate AM transmitters. It is only used for SSB transmitters which radiate no carrier so the power is totally related to the signal level of the audio being transmitted) .When modulation is added the power output rises. For example if 100 % modulation is being broadcast the output power of the transmitter increases by 50 %. This results in the carrier being 67 % of the fully modulated radiated signal compared to silence which is 100 % of the radiated signal.

        The only modulation which has a constant output power is an FM signal as there is no information in the power of the signal. As a result receivers cut any power variations usually caused by losses in the air out by a circuit called a limiter.

        DRM uses 4 or 16 power levels and 4 or 16 phase to represent each digital number, this is then Fourier transformed into hundreds of separate signals which vary in levels accordingly prior to transmission. (The 4 x 4 system is more resistant than 16 x 16 to noise and interference but the available data rate drops)

        DRM power ratings are an average of the transmitted power over time because the total power level varies. A 100 kW AM transmitter can only produce a long term average of a DRM signal of 50 kW leaving headroom for the variation of signal power. This is because there is no fixed level of carrier transmitted. I should add that pure digital HDradio in the AM band retains the wasteful carrier.

        DRM is not related at all to the AM stereo systems to which you refer. It uses Orthagonal Frequency Division Multiplex. None of the AM stereo systems used Independent sideband ie the lower sideband for the left channel and the upper sideband for the right channel. They all used variations of amplitude modulation for the Left + Right (mono signal) and the Left – Right signal is phase modulated onto the carrier.

    2. Mangosman

      See my comments below.
      For your proposal it is a pair of single sideband transmitters using a common carrier frequency. Have you ever heard music on SSB?

      Consider a transmitter operating at 1 000 kHz. For broadcast you would need to produce a lower sideband 991 000 – 999 970 Hz and upper sideband from 1 000 030 Hz – 1 009 000 Hz and . It is extremely hard to get a filter at that frequency to eliminate the frequencies from the other sidebands 60 Hz away. As a result there is crosstalk between left and right which makes it mono.

      You forget about there is no protection from noise in AM transmission systems and with the invention of the switchmode power supply which is used in nearly all electrically powered devices, more power line insulators… AM radio sound is becoming worse. DRM will ignore it all provided the signal is above a threshold which is much lower than the signal to noise ratio required for normal AM listening.

      The BBC transmits DRM from Woofferton UK for NE Europe at 0559-0700 UTC on 3955 kHz using 100 kW of power.

    3. Mangosman

      For More information
      I suggest you look at the official website of the Digital Radio Mondiale Consortium, which is non profit.
      it is www dot drm dot org and in particular the handbook. I used the word dot instead of the symbol so that this post not be stopped by the publishing filter.

  4. Steve

    My only real interest or perhaps concern is How will this change affect the reception range of clear channel and higher power AM stations during daylight and dark hours when the locals may be down due to weather or other events.

  5. Babis

    while it will need a good power signal, soon or later some will follow digital … best option is to use one system, example DRM because we will not need different radio to hear one station and an other radio for an other station

  6. Jake Brodsky, AB3A

    Once again, the FCC lawyers are making stuff up.

    I listened to WWFD on AM before they went digital and then afterward with the digital signal. While it wasn’t a great sounding signal, it was listenable in Analog in my vehicle (which is pretty much where most people would listen to AM). In digital most of the areas where I often got a listenable signal were gone. The radio in our new vehicle is otherwise comparable to the other radios I used to listen to WWFD.

    To be fair, when it works, the all-digital signal sounds very good. But the signal cuts in and out well within the defined areas that WWFD claims to cover.

    I wish the FCC had named which digital protocols would be used in channel. I think DRM would have been a safer bet. But then again, if there is a choice those clowns at the Federal Communications Commission usually pick the wrong one.

    1. Babis

      each technology (analog or digital) has plus & mines, which will not go into it … everyone can say their opinion (positive or negative) as long is not personal to other users, so with respect why post removed? is not nice to read to an independent blog post removed, Thanks for understanding

      1. Mangosman

        It is simple. In pure digital HDRadio in the AM band, the maximum digital power is 6 % of the carrier power. In AM the sound with the greatest volume is up to 33 % of the transmitted power. The carrier contains no information or sound but is required by AM receivers to demodulate the signal.

        By comparison DRM contains no carrier at all. Therefore the digital signal is nearly 100 % of the transmitted power.

        Therefore the coverage area of the pure digital reception of HDradio is much less than AM and DRM.
        The sound quality of DRM which uses the new xHE-AAC audio compression algorithm is capable of producing much better sound than that of HDradio at the same low bit rate. DRM also carries more data than HDradio in the same bandwidth.

        1. Keith Perron

          DRM no longer stands for Digital Radio Mondial, it stands for Doesn’t Really Matter. I was at the launch of DRM more than 20 years ago and nothing has come of it. All the major manufactures that were part of the consortium have pulled out. The DRM Consortium is very good at making presses releases. Any investment in DRM today would be like investing in a new VHS machine.


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