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AM STEREO AIRCHECKS



WWFD

WWFD(AM) "THE GAMUT" FREDERICK, MARYLAND IS U.S.A's FIRST MEDIUM WAVE ALL-DIGITAL HD RADIO STATION

On July 16, 2018, station WWFD(AM), in Frederick, Maryland USA, "The Gamut" made history to become the first AM medium wave broadcast station in the country to transmit a stereo audio music format, testing the HD Radio all-digital MA3 mode full-time, under an experimental license from the Federal Communications Commission (FCC).   WWFD(AM) is operating at 4,300-watts (daytime, non-directional pattern); and at 430-watts (night, directional) using the AM "all-digital MA3 xPeri service mode" and boasting a musical playlist of more than 20,000 songs.   WWFD also operates their 160-watt horizontal polarization monaural analog translator FM station, W232DG, simulcasting the 820kHz AM digital signal, at 94.3MHz, with RBDS scrolling text program information.

With most of its listeners having migrated to its FM translator in Frederick, Maryland (acquired in the AM Revitalization proceeding), the WWFD licensee, Hubbard Broadcasting Radio, decided to experiment with the possibility of higher audio fidelity and increased reception area using the unique all-digital signal.   It then promoted its all-digital AM station on its FM translator.   Detailed information regarding the technical aspects of the WWFD facility modifications were presented at the 2019 NAB Broadcast Engineering and Information Technology Conference and published in the WWFD Paper.   Hubbard reports that it has experienced significant improvement in WWFD's audio quality and signal robustness in the all-digital mode (testing indicated reliable daytime coverage to at least the 0.5mV predicted contour, and night-time coverage to the night-time interference free (NIF) contour).

This WWFD experiment illustrates the potential benefits of all-digital broadcasting for AM stations and their listeners, particularly regarding audio quality and signal coverage area.   WWFD continues to operate under its experimental all-digital license, with the Engineering STA renewed every year with the FCC.

Xperi's HD Radio system primarily has two operating AM service modes: hybrid analog/digital (MA1) and all-digital (MA3).   A hybrid transmission consists of a combination of analog and digital signals, with the analog signal typically occupying bandwidth of 5kHz on either side of the center carrier radio frequency, with simultaneous digital OFDM carriers modulated in quadrature on either side of, and underneath these analog signals.

In an all-digital mode, the number of OFDM quadrature digital carriers is increased, and moved closer towards center frequency with increased transmission power, resulting in a more robust digital signal, that is less susceptible to adjacent channel and other interference.   Programing modulated analog carrier signal does not exist, therefore all analog receivers and analog tuners cannot properly demodulate the all-digital MA3 signal.   Rather, the receiver will seek, stop, and successfully lock to the center carrier frequency, and demodulate a very loud hissing sound for the listener.

Both MA1 and MA3 modes permit operation within the existing allocations and channel spacing framework authorized by the FCC, and are designed to fit within the relevant Commission emissions limits.   NRSC has not tested nor evaluated the MA3 mode, although all-digital operation is included in the NRSC-5 IBOC standard.   The HD Radio digital technical operating parameters are set out in the NRSC-5 standard and in periodic publications issued by iBiquity/HD Radio (HD Radio Specifications).

WWFD_Coverage_Map

meduci, LLC had an opportunity during Easter holiday weekend 2022 to listen to WWFD, with driving around their Frederick transmitter site location.   Our vehicle's stock non-HD Radio treated MA3 service level with recovering a very loud, and constant hissing sound. Yet the radio still was able to seek, find, and to stop on the MA3 beacon frequency, at a distance of up to 47 miles north from Frederick, MD.   This is likely how all analog-only AM radios will sound tuned to MA3 HD Radio stations, when the AM broadcast band gets more populated with them.   Incidentally, WCHA(AM) in Chambersburg, PA (two channels away) was not affected by WWFD.   We really need to go back to Frederick for a return visit, and farm out the listening range of WWFD's MA3 signal, using another vehicle equipped with HD Radio.   Listening to MA3- compared to MA1 in the past- during this Easter weekend, five miles east from the WWFD transmitter location, was like night and day differences.

MA3 has good fidelity and stereo separation, and sounds like it has legs, and will be a good keeper on the AM broadcast band.   MA3 seems to be more robust and stable than the MA1 broadcasts, previously received from 50,000-watt AM stations in the past on Coby and other representative HD-capable tuners.

Overall, WWFD sounded amazing, and the station is engineered very well.   This was our first time hearing HD Radio full bandwidth MA3 on the medium wave band (having listened to AM stations since 1973).   Our honest opinion so far- MA3 sounds very good!   And certainly much better than MA1, during the very in-frequent times that we struggled to receive lock from several class A stations, that were transmitting in hybrid analog/digital mode about ten years ago.   Our two local 50,000-watt AM stations have since abandoned MA1 for the same reasons that we saw: limited and unpredictable HD station lock from HD Radios, massive adjacent channel analog interference, and significant audio artifacts (shrill and artificial; not natural sound).   This MA3 is MUCH more robust signal, acquires lock faster, and stays locked.   Audio codec is obviously the same; though, it sounds like the number of digital bits in the transmission mode has increased, which reduces the synthesized sound in the higher frequencies.

Dave Kolesar, Chief Engineer and Program Director for WWFD, says, "The bit rate for MA3 is about 40kBps, and we've got about 4kBps set aside for album artwork and station logo.   So what you're hearing is about 36 kBps.   In the fringe areas the radio only picks up the core signal and the bit rate reduces to 20kBps parametric stereo.   I'm always listening critically and learning.   The station sounds better than it did six months ago, and it may sound even better a month from now.   How the signal handles lightning depends on how close you are to the transmitter, and how close the lightning is.   If you're within the 2mV contour, most times buffering would handle the dropouts.   Further out, the signal may be interrupted for about a second.   In the deep fringe areas, like analog, the signal probably won't be useful."


Listen to this off-air selection from the Marvelettes (song was written by Marvin Gaye) during the Motown era in full AM stereo HD Radio here:
WWFD_THE_GAMUT
  • In this video, we had deliberately caused the music program dropout at 2:25- by tuning away and back to WWFD- to demonstrate how much time was needed for the tuner to lock back on and to process the HD RF signal.

  • INXS, song Mystify, recorded here:
    WWFD_1

    Monty Python, and Always Look on the Bright Side of Life, recorded here:
    WWFD_2

    The Four Seasons, singing Save It For Me, recorded here:
    WWFD_3

    Sunday morning public service programing- For Your Ears Only; listen from here:
    WWFD_4
  • We were caught listening back and forth between the FM analog monaural simulcast from the 94.3MHz translator station, and the AM digital MA3 broadcast, on the same radio.

  • RUSH sounds awesome on AM digital stereo, yelling for A Farewell to Kings:
    WWFD_5
  • Comparisons made again between the monaural FM analog translator station, and the AM digital MA3 broadcast.
  • PLEASE NOTE: Undoubtedly, you will hear unintentional compression artifacts from the WWFD recordings, that were not present in the source broadcasts. These were caused during conversion from the recorder's native format to AAC 48kHz audio sample rate. These MP4 files were not meant for critical listening; only simply for you to enjoy the new sound to be heard on the AM broadcast band.


    MEDUCI RADIOS: IT ALL BEGINS WITH OUR CUSTOMERS !!!


    TAKUYA KADOWAKI PROVIDED TWO AUDIO FILES FROM HIS MEDUCI AMX2000 TUNER IN JAPAN

    Takuya Kadowaki shared two air checks, as recorded from his meduci AMX2000 tuner in Japan in July 2008.   Please listen and let us know your thoughts:

    AM STEREO IN JAPAN FILE ONE (3.4MB)

    AM STEREO IN JAPAN FILE TWO (3.1MB)

    MEDUCI PRO1k TUNER WAS INCLUDED AS PART OF THE ROBB RADIO SHOW AND "THE MIGHTY 1630 KCJJ" AM STEREO BROADCAST

    Courtesy of Colonel Tab Patterson, Robb Spewak, Captain Steve (Soboroff) Bridges, and KCJJ-AM, listen to the "Robb Radio" show recorded live from Coralville, Iowa USA.   This was a four-hour music program that originally aired on November 5th, 2010.   Tab used his meduci PRO1k tuner approximately seven miles from the KCJJ transmitter location to receive the show in full C-QuAM stereo with very wide stereo separation being evident.   Your ears are in for a very nice treat!   You can download the entire show at once, or get it in one-hour time blocks>> Robb_Radio_Show_110510

    This direct off-air recording from KCJJ demonstrated how well analog AM stereo rules, and showed the full potential for C-QuAM stereo fidelity.   This is despite NRSC-2, and the other restrictions being placed on the transmission technology.   To hear the entire 201-minute show (provided that you have a robust Internet Service Provider capable of uninterrupted downloads), you can save the entire MP3 clip from this link>> robb_radio_20101105_entire_TRSS_November5_2010_CQuAM (378MB)

    Robb Spewak enjoyed spinning the records live in the River City Radio KCJJ studio.   Music selection ranged from the Beach Boys, the Offspring, Jerry Reed, the Moody Blues, to Bad Company, and other musical groups ... there was true variety, keeping in line with the KCJJ format.   You may remember Robb as the third wheel on the "Don & Mike" show for many years.   Captain Steve recently celebrated his golden fifty year anniversary in broadcasting.   He started at 16 years of age on WGEN(AM) in Geneseo, Illinois and worked at stations in Muscatine, Iowa, Waterloo, Iowa, Chicago, Des Moines, and the Quad Cities, and has owned KCJJ since 1994.

    INSIDE "UNDER THE HOOD" TO THE FIRST SIMPLIFIED PROTOTYPE MEDUCI PRO1k AM STEREO TUNER:

    First_PRO1k

    TAB PATTERSON RE-VISITED KCJJ(AM) WITH A FIRST-EVER HISTORIC QUADRAPHONIC RADIO BROADCAST CAPTURED USING HIS MEDUCI PRO1k TUNER!!

    On April 14th 2011, Tab Patterson again visited the Robb Spewak Show on KCJJ in Coralville, Iowa USA and made radio history with his successful Quadraphonic Radio test over C-QuAM stereo technology!   USTREAM had a clip at one time that contained the direct live audio feed from the studio, as well as video taken from a stationary camera.   Quadraphonic test began at approximately 30 minutes into this video stream.   Left and right channels were reversed on the USTREAM feed.   You can also watch Tab Patterson's video that takes the over-the-air sound recording from KCJJ using his PRO1k tuner.   This video demonstrates how good AM stereo can sound, with very wide separation, and very low total harmonic distortion being present!   To properly play this video, connect your computer to a Dolby Pro-Logic receiver and set the decoder to the "music mode."   You should hear very defined vocals and musical instruments move throughout all four speakers.   This was a 12-minute long experimental broadcast to see if Quadraphonic Sound could indeed be encoded, transmitted, received via the meduci PRO1k, and successfully decoded (using Dolby Pro-Logic II) back into true Quadraphonic Sound, and four discrete audio channels, using conventional AM analog broadcasting technology.   This proves that it is possible to get surround sound using an AM radio signal.   First click on this link to listen to the Quadraphonic broadcast>> Robb_Radio_Show_Quadraphonic_MP3

    Tab was roughly seven miles from the KCJJ transmitter (actually in back of their on-air studios on Quarry Road) inside his pickup truck, using his PRO1k with his>> TERK Technologies Audiovox AM Advantage 1000 passive antenna), which he placed on the roof of his truck.   It was windy that day, and the antenna was rocking back and forth.   As the antenna moved in the wind, the antenna patch cable briefly lost contact with the Terk's 1/8-inch connector jack.   This caused the received C-QuAM signal to briefly lose stereo lock twice during the Lighthouse recording.   Tab believes that the studio structure actually helped block the adjacent AM iBiquity HD Radio station on 1600kHz from interfering with the historic Quadra-cast sound broadcast on 1630 kHz.   Two of the three songs were directly played from quadraphonic 8-Track tapes in the KCJJ studio.   The song from Chicago was encoded using the Rhino DVD surround sound release of the original Quadraphonic album.   This is really pushing C-QuAM technology to its limits because the audio phasing has to be perfect!   We hope you listeners enjoyed this Robb Radio Show special treat!   Perhaps you were lucky to hear it live OFF-AIR from KCJJ using your Dolby Pro-Logic home audio system receiver modified with an AM stereo decoder!?!

    Due to your enthusiastic e-mail requests, we now offer Tab's full 12-minute audio file (16-bit WAV sound format) that you can download to your audio file collection!   This WAV file does not make use of any digital audio compression or resulting artifacts, therefore it is a large file.   To save the file to your computer, you first right click on the file name called "KCJJ_Quadtest_PRO1K" below, then (depending on the functionality of your web browser), select "Save Link As..." or "Save Target As..." then choose your destination for the audio file to be saved, then (depending on your ISP connection speed) grab a cup of coffee (or several cups)>> KCJJ_Quadtest_PRO1K (132MB)

    You can also watch and listen to the actual epic quadraphonic AM STEREO recording here, from the direct connection to Tab's meduci PRO1k tuner.   To save the file to your computer, you first right click on the file name called "KCJJ_Quadtest_MOVIE" below, then (depending on the functionality of your web browser), select "Save Link As..." or "Save Target As..." then choose your destination for the file to be saved, then (depending on your ISP connection speed) grab a cup of coffee (or several cups)>> KCJJ_Quadtest_MOVIE (436MB)

    Please note that you will not be able to stream this file from this web site.   You should be able to save the file to your computer following the above instructions!

    Sadly, KCJJ elected to discontinue their AM stereo broadcasting in November 2012.   From KCJJ: "We could not justify sacrificing almost 15 percent of our modulation to a technology that isn't available anymore.   It's sad, because it did work nicely, but our local coverage did improve, and we could no longer get service on the exciter.   Thanks for listening.   KCJJ Staff."   Ironically, Robb Spewak said to Captain Steve (Soboroff) Bridges at the end of his 12-minute legendary quadraphonic broadcast:

    "Remember Steve, it's twice as good in stereo."

    Two monaural AM stations had contacted us, and will be converting their transmission plants and studios to AM stereo in USA.   We will announce new AM stereo launches at these two AM stations when they are ready.   It seems that for each AM stereo station that falls, another one rises in its place.   Stay tuned to meduci's web site for further updates!   And please remember to promote AM Stereo at least ten times per day on your station -- in hourly station identification: call letters, followed by community of license, followed by the magical two words "AM STEREO" !!   And regularly promote AM Stereo on your web sites, with the two words "AM STEREO" listed in your station logo!   This promotion will make a big difference with engaging your listeners.


    CFCO

    CFCO (AM) 630kHz in Chatham-Kent, Ontario Canada was air checked on Friday, February 3, 2006 from 60 miles distance to Oakland county, Michigan USA.   This stereo music was broken down into eight discrete files, as recorded using meduci AMX2000 stereo tuner radio line audio outputs.   Then these two audio outputs were fed directly into Dell desktop computer's sound card to Microsoft Windows-based WAV file recorder, and finally converted to MP3 digital audio playback format to conserve space and file download time.

    CFCO is absolutely awesome, still broadcasting C-QuAM stereo in a different music format now.   And since CFCO was not obligated to have the USA NRSC-2 filter inline, their high frequency response is also excellent.   These air checks are reminiscent of older AM radio broadcasting, where audio frequencies were not brick wall cut-off at 10.2kHz in USA.   Keep in mind that the station was on their 10,000-watt daytime directional antenna pattern, and their main lobe was not directed to the southeastern Michigan area.

    You can save the entire MP3 clip from these eight links below (switch to night time pattern is evident in file eight, and file seven shows the difference in audio quality from the Terk AM Advantage 1000 tunable loop antenna, in comparison to a simple un-tuned unity gain AM plastic loop antenna connected to the meduci AMX2000 tuner).

    To save the file to your computer, you first right click on the file name below, then (depending on the functionality of your web browser), select "Save Link As..." or "Save Target As..." then choose your destination for the audio file to be saved, then (depending on your ISP connection speed) grab a cup of coffee (or several cups)>>
    CFCO-02-03-06-meduci-amx2000_1
    CFCO-02-03-06-meduci-amx2000_2
    CFCO-02-03-06-meduci-amx2000_3
    CFCO-02-03-06-meduci-amx2000_4
    CFCO-02-03-06-meduci-amx2000_5
    CFCO-02-03-06-meduci-amx2000_6
    CFCO-02-03-06-meduci-amx2000_7
    CFCO-02-03-06-meduci-amx2000_8

    System modifications were made in February, 2000 so that CFCO's authorized daytime and night time antenna patterns could be improved.   All work was completed and CFCO(AM) was now operating with their 1999-approved technical changes, including a night-time power increase to 6,000 watts from 1,000 watts.   At that time, a new Nautel C-QuAM AM stereo transmitter was also installed and deployed.   A new low power FM stereo translator was also put into service on 92.9MHz to fill in some in-building coverage gap in the city.


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