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Announcing the death of ugly AM radio sound!

Welcome to the world of AM high fidelity and meduci wideband AM stereo quality sound, day and night.   The future of radio is now.   Better reception.   Better sound.   At meduci, we are very passionate about good quality sound. meduci has AM stereo radios for sale.

Many radio manufacturers are leading you, the consumer, to believe that AM radio sounds literally abysmal!   Radio manufacturers have, by cutting corners and costs, tossed aside a medium that can sound as good as FM radio broadcasting, and reach a farther listening area.   In many communities, an AM station is the only LOCAL live media!   It deeply angers meduci that public perception of what AM "sounds" like should be garbage, when in actuality- its potential goes far beyond what most people have ever heard!   We hope that when you hear a good AM stereo station proudly speaking about their "sound" that you realize it is your current RADIO product that limits the quality of what you hear, not the AM medium wave band itself!

America's economy is driven by purchases, and purchase price is certainly a determining factor.   However, that DOES NOT mean that saving a few pennies here, or a dollar per unit there, to improve the quality of AM sound in radios, would break the manufacturer, or the consumer.   This explains why we did not cut corners when designing and manufacturing our own AM stereo products.

We have adopted Motorola's C-QuAM®™ analog stereo AM technology, and are proud to offer the latest integrated circuit decoder technology available for C-QuAM™ stereo tuners, to provide optimum and accurate AM stereo performance.   We re-launched AM Stereo in October 2005, and we gave C-QuAM™ a second chance in the marketplace by introducing four new AM stereo products since then.   These AM stereo products cannot be purchased anywhere else.   Customers are very satisfied with their meduci tuners.   Satisfaction is so high that meduci tuners are not re-sold on eBay.   Each meduci product is also backed with one-year warranty against defects in material and workmanship.   We use ORIGINAL McCoy Motorola IC chips and other prime components in every meduci AM STEREO product.

There are many AM medium-wave stations broadcasting wideband full fidelity sound in different parts of the world.   When received using an appropriate wide band high fidelity AM stereo receiver or tuner under good conditions in the reception environment, using a good external indoor tunable loop antenna, the recovered noise-free high definition sound is virtually indistinguishable from many high quality FM stereo broadcasts!   Hearing is believing!   Sample one of our high definition AM stereo products, and judge the enhanced audio fidelity for yourself.


model: Moto model: AM_ST_front_1 model: AM_ST_front_tri_color model: AM_ST_backb model: AM_ST_front_2



This high-quality and low-cost solid state add-on after-market AM stereo decoder printed circuit board circuitry is hand-made, assembled, and tested (not a kit!), with new attractive green printed circuit board, new ceramic resonator offering wider stereo lock-in frequency range, and the circuitry is based upon the popular third-generation Motorola MC13028AD stereo decoder chip, which has balanced full-wave envelope detector for the L+R (mono) channel, which is technically better than the half-wave diode envelope detectors used in garden variety AM tuners and receivers.  This full-wave detector maintains audio levels better under varying signal conditions.  For the do-it-yourself person, this 1.675" x 1.5" (42.5mm x 38.1mm) sized board will easily and economically convert your own tired sounding AM mono electronic digital-tuned (ETR) donor receiver to stereo reception using the Motorola C-QuAM broadcast AM stereo standard (where available).   This board accepts the signal from the 450 kHz I.F of AM receiver, and decodes stereo medium-wave MW broadcasts.  This design improves audio fidelity, due to the very low total harmonic distortion encountered (typically under one percent, and inaudible to the human ear)! This board operates at +10 to +15 Volts D.C input, and provides standard line level left and right audio outputs, for direct connection to the receiver's audio amplifier.   It may be used to support 30Hz to 15,000Hz audio frequency response; however, much will depend on the bandwidth of your AM receiver's front end strip.   Instructions are included for typical installation to AM receivers.   There is also an on-board eight-volt linear-mode I.C voltage regulator included.   BONUS:To widen the audio bandwidth in your donor host AM radio, one new muRata CFU450B black ceramic filter is also included pre-installed on-board the AM_ST decoder, free of charge, with each new purchase.   Good news is that this wide bandwidth filter will dramatically increase the recovered audio bandwidth from your AM_ST decoder.   As shown below, previous AM stereo conversions required that the existing tuner's low bandwidth tuner filter to be unsoldered, and then removed.   And the new replacement wide bandwidth filter to be installed on the tuner board, in place of the existing filter.   This would bypass the existing narrow bandwidth I.F and allow for better overall high frequency response from the converted AM medium wave tuner or receiver.   However, during the actual conversion to AM stereo reception, sometimes it was difficult to get access to the bottom side of some of the tuners.   Now you simply tap off prior to the input to the existing I.F filter, usually at the output of the last I.F transformer, then to the yellow wire on the AM_ST decoder board.   Having the new ceramic filter on the AM_ST decoder makes for an easier conversion, and also reduces or eliminates some stray out-of-band interference from shortwave and other stations.   Simply bypassing the on-board 450kHz ceramic filter will facilitate 455kHz I.F input and operation from this AM_ST decoder module.   In addition, Forced Mono feature is included on-board.   Schematic diagram and details are also included with each purchase.   We provide free technical guidance for one conversion per each AM_ST decoder purchased, and include web page hyperlink to an eight-page comprehensive instruction manual with every order!   We want you to succeed with your AM stereo conversion project.   You can send us e-mail ahead of purchase to see if your tuner is compatible with this AM_ST decoder board.
FYI- USPS is experiencing unprecedented volume increases and limited employee availability, due to the impacts of worldwide pandemic.   We appreciate your patience for waiting to receive your order.

Assembled and tested decoder board:
New prices effective now: $35.00 USD each (to domestic USA address, with free first class shipping service), or $45.00 each to any PayPal confirmed shipping address virtually anywhere else within the world, with free first class shipping service.  Tuner/receiver is NOT included with your purchase.  Prior to purchase, please ensure that there is adequate space inside your host donor receiver to be converted to AM stereo.  There are six internal connections to be made to your receiver (>+10-volt D.C power, chassis ground, 450 kHz I.F input, stereo LED driver output, left channel audio output, and right channel audio output).  

Purchase details are located here:

International ship suspended.

This is a stocked item, and is available for immediate shipment after your PayPal payment clears to our financial institution account.  This decoder is new and directly sold from the manufacturer.   Assembled in the United States of America from U.S.A and globally-sourced parts.

new For AM Stereo Stand-Alone AM_ST Decoder Owner's Manual, please click on this link.


  • Carver TX-2
  • C.Crane CC Radio-SW
  • Delco 16194955
  • Delco 16138062
  • Denon TU-1500RD
  • J.C Penney MCS3050 (Model Number 683-3050-00 - Catalog Number 853-6641)
  • Kenwood TS-140S
  • Kenwood KT-727
  • Kenwood KT-6040
  • Kenwood BASIC T2
  • Marantz ST-6000
  • Marantz ST-6001
  • McIntosh MR7084
  • McKay-Dymek AM 5
  • NAD 7140
  • Onkyo T-422M
  • Onkyo R-805X
  • Panasonic SA-AK33
  • Pioneer SX-5
  • Pioneer SX-6
  • Pioneer TX-950
  • Pioneer F-227
  • Redsun RP2100
  • Sansui TU-X1
  • Sansui 5050
  • Sanyo M7850K
  • Sony STR-DE525
  • Sony STR-GX47ES
  • Sony ST-JX430
  • Sony ST-JX220
  • Sony ST-S311
  • Teac T-H500
  • Yamaha TX-492

  • PayPal Proposition 65


    Pioneer F-227_1

    In this corner, we will spotlight current projects for our meduci AM_ST outboard decoder module!   Richard Prinsloo from Johannesburg, South Africa wanted to convert his Y2K model Pioneer F-227 AM/FM PLL tuner to AM stereo reception with the meduci AM_ST converter board.  Richard did not have the tuner's service manual; however, meduci was able to locate four poorly scanned, though readable, pages online- as taken from the actual Pioneer service manual.  Even though these four pages were incomplete, there was enough information to make a decision on how easily it would be to add the AM_ST decoder card in Richard's Pioneer host donor medium-wave AM receiver tuner.

    This tuner board seemed to be planned for some future AM stereo implementation, as there is a vacant six-pin header labeled "J3" next to an "AM STEREO" caption.  This appears to be a provision for connecting a future AM stereo module.   Four pages of the scanned service manual did not show nor address how this "J3" header connection was to be provisioned (shown below):

    Pioneer F-227_1a

    During Richard's tuner modification, he successfully replaced the existing stock ceramic filter.  He unsoldered and removed this small one-piece integrated white component from the bottom side of the tuner board, and separated the filter from the I.F transformer can:


    He re-installed the I.F transformer and replaced the stock ceramic filter with muRata black CFU-450B filter. Richard did not need to make use of the empty "J3" header when following our simple AM_ST decoder installation instructions:

    Pioneer F-227_2

    Richard writes, "Good news!!   I have successfully installed the decoder, following your detailed instructions.   I now have AM Stereo on my Pioneer F-227 Tuner.   The "STEREO" indicator even works on AM now.   I installed the new I.F filter first and tested the tuner after that.   All was still working fine.   Then I made all the connections to the tuner, and cut the audio path after the capacitor."

    Pioneer F-227_3

    It was evident that frequency response did improve using our AM_ST decoder, since the Pioneer F-227 tuner's internal audio filters were bypassed after the successful modification was performed.  Ultimately, the overall response was initially limited by the stock 450kHz I.F ceramic filter used within this tuner prior to AM stereo modification.  Since so many existing AM mono receivers were sold with low audio bandwidth (on the order of ~3kHz), we included one new muRata CFU450B black ceramic filter with Richard's new AM_ST decoder purchase.

    Pioneer F-227_4
    Pioneer F-227_5
    Pioneer F-227_6



    Bent Kyllesdal from Norway made his Sony ST-S311 FM stereo/medium wave AM monaural tuner sing much better thanks to economical meduci AM_ST card.  Convenient tap-off points are present on the Sony tuner main board.

    During Bent's tuner modification, he successfully replaced the existing stock ceramic filter.  He used one new muRata CFU-450B filter that was provided free of charge with his AM_ST decoder purchase.  This black ceramic filter dramatically widened the recovered audio fidelity, compared to the previous sound heard from the stock ceramic filter:


    This is the underside of the tuner board showing the left and right audio connections to Sony audio pre-amplifier I.C chip:

    You can watch Bent's video from here:
    playback button Play the video by clicking here>> After AM stereo modification to SONY ST-S311 tuner.


    Denon Inside

    Bent Kyllesdal from Norway made his Denon TU-1500RD FM stereo RDS/medium wave AM monaural tuner sound much better after his AM_ST card was mounted inside. Full C-QuAM stereo fidelity was realized from his AM stereo transmitter. He was also very pleased with the customer support he received from meduci, LLC.  We were there every step of the way to answer Bent's questions. We provide free technical guidance, and provide full conversion instructions with every meduci AM_ST decoder purchase; one conversion for each purchase. We want you to succeed with your AM stereo conversion projects.

    Convenient tap-off points are present on the Denon tuner board, so it was a very simple conversion for Bent.  Much of the stock tuner was retained.  One leg of the existing audio coupling capacitor (C141) was snipped on the tuner board, that came from pin 12 of IC101 (AM tuner I.C chip), to pin one of IC102 (FM MPX stereo decoder I.C chip), to disable the monaural AM audio output path.   Two series resistors were added from the AM_ST decoder left and right audio outputs to the tuner's audio amplifier I.C chip.   Switched B+ D.C voltage from the AM tuner I.C chip was also a convenient source to power the AM_ST decoder.   This ensured that the AM_ST decoder was powered down when tuner was switched to FM band.   Therefore, any stray audio would not be present from the AM_ST decoder to leak through when tuning FM stations.

    During Bent's tuner modification, he also successfully replaced the existing narrow bandwidth stock ceramic filter.  He used one new muRata CFU-450B filter that was provided and included free of charge with his AM_ST decoder purchase. This black ceramic filter dramatically widened the recovered audio sound stage, compared to the previous sound heard from the stock filter (shown on the right side below):


    Denon's TU-1500RD microprocessor "locked out" or failed to read the "ST IND" pin from Bent's AM_ST decoder when in AM medium wave mode.  Unfortunately, this is very common with many tuners.  To overcome this tuner design limitation, Bent added a separate light emitting diode (LED) underneath the front panel display window for AM stereo indication.   Bent also discussed his phenominal achievement on Facebook.

    You can watch Bent's videos from here:
    playback button Play the video by clicking here>> DENON TU-1500RD tuner.
    playback button Second video is here>> Another video for DENON TU-1500RD tuner.


    McKay Dymek AM5 tuner

    XRAYTONYB from Volant, Pennsylvania USA was up to the challenge to modify his customer's McKay Dymek AM5 solid state medium wave band tuner to receive C-QuAM AM stereo broadcasts, using the economical meduci AM_ST decoder.   This high-end AM-only tuner, very popular during the mid-1970's, has a very large intermediate frequency (455kHz) output level, which needed significant signal attenuation (or "padding"), in order to properly drive the composite baseband input to the AM_ST decoder, without overloading or "swamping" the module's I.F input.   Fortunately, this McKay Dymek tuner also offered other simple and convenient tap-off points for power, audio, and stereo indication.   XRAYTONYB added a blue stereo LED indicator that glows inside the front panel S-meter.

    Fun stuff Fun staff again
    You can watch the entire XRAYTONYB video from here (without commercial advertisements):
    playback button Play the video by clicking here>> AM stereo modification to McKay Dymek AM5 tuner.

    In this video, XRAYTONYB also discusses the best antenna matching for proper output power transfer, and demonstrates tips for building the transmitter into a metal case using quality rechargeable 18650 lithium-ion high power capacity battery power supply to the Alfredo Torrejon-designed ALFREDO LITE CCUFF low-power AM stereo C-QuAM test transmitter.   This is a low power type of C-QuAM signal source.   Without having antenna on hand, matched and resonant to the transmitter's R.F output, the listening range was limited to a few feet.   We have two such part-15 compliant type AM stereo C-QuAM test transmitters, and the range is also limited from either transmitter to the receiver's AM external tunable loop receiving antenna.   We use our two transmitters to test our AM_ST decoder modules, prior to shipment to customers.   In order to increase this transmission range, you will need the three meter long AM medium wave transmitter properly mounted outside, connected with very short shielded cable to the transmitter's low power output, and also connected to a very healthy buried ground radial ring.   Plans are widely available on the Internet.   We cannot recommend any FCC-compliant C-QuAM transmitters and outdoor antennas at this time, though.


    Sansui TU-X1 tuner

    XRAYTONYB modified his customer's Sansui TU-X1 super integrated tuner, to add AM stereo reception using the reliable and economical meduci AM_ST decoder.   In this tuner, it was easy to tap off the interior power, audio, I.F and stereo connections.   This Sansui tuner was designed prior to the worldwide standardization to the C-QuAM AM stereo format; therefore, like other tuners during this era, this Sansui has an outboard AM stereo output jack on the rear panel. These special output jacks were meant to drive external AM stereo decoders, that never materialized in the marketplace.

    Sansui is tall. the big picture.

    This is both AM and FM model using 455kHz intermediate frequency for the medium wave band, which was an industry standard for manually-tuned (non-automotive) AM tuners.   XRAYTONYB discusses how he modified the tuner, and shows where the internal tap-off point exists for the AM_ST decoder from the Sansui tuner.   It is also an easy task to revert this tuner back to stock condition, and remove the internal AM stereo decoder module.

    You can watch the entire XRAYTONYB video from here (without commercials):
    playback button Play the video by clicking here>> AM stereo modification to Sansui TU-X1 tuner.


    Phil 'Tha Dood' from Poca, West Virginia USA purchased two meduci AM_ST decoders from eBay, knowing which products he wanted to be converted.   One of the modifications was a rather high end deluxe McIntosh MR7084 tuner (domestic model made in New York, USA). We reviewed the service manual that he provided, and we supported the modification, by providing the connection details from this host tuner to his AM_ST decoder.   And the results?   AM stereo broadcasts could be successfully received for the first time!   "I think better than the FM stations on this tuner," Tha Dood says.   "Amazing!   Whatever fidelity that transmitter is capable of, this tuner now hears it."

    Tha Dood has his own medium wave carrier-current station at 610 kHz, with FCC part-15 compliant radiating station at 1620 kHz, and a low-power unlicensed AM Stereo test transmitter from Sean Cuthbert operating on 1580 kHz.   He also operates a web site called Real Free Radio where his music play list can be found.   His current activities are also dicussed.

    For the McIntosh MR7084 successful tuner modification, Tha Dood highlighted in yellow the components affected, or changed, from the tuner board layout page, as taken from the McIntosh service manual:
    McIntosh PC board modifications

    Much of the stock tuner was retained.   One capacitor (C93) was removed, that came from pin 12 of IC2 (AM tuner IC chip), to IC5 (FM MPX stereo decoder IC chip), to disable the monaural AM audio output path.   Series resistors were added from the AM_ST decoder left and right audio outputs to the tuner's audio amplifier.   Switched B+ D.C voltage from the AM tuner IC chip was also a convenient source to power the AM_ST decoder.   This ensured that the AM_ST decoder was powered down when tuner was switched to FM band.   Therefore, any stray audio would not be present from the AM_ST decoder to leak through when tuning FM stations.   Front panel MPX LED stereo indicator was also able to be used, and was a simple connection to the AM_ST module.

    This is the interior view showing the six wire connections from the meduci AM_ST decoder to the McIntosh tuner board (tap on the pictures to enlarge them):
    McIntosh AM MPX LED Indicator

    McIntosh Interior View


    This McIntosh tuner had one stock blue muRata SFG450D ceramic filter after the tuner's mixer stage, which was capable of 10kHz recovered audio response.   Tha Dood was able to remove that SFG450D filter, and replace it with one new black muRata CFU450B ceramic filter that was included with his AM_ST decoder purchase.   It was a direct drop-in replacement.   McIntosh also made accommodation on their tuner board for a five-pin ceramic filter, and the two empty holes on the board were used as I.F output to the AM_ST decoder.

    For the front panel illumination, Tha Dood also removed the six incandescent "wheat" 7373-style light bulbs that came with the tuner, and replaced them with six white LED indicators.   This should increase reliability, and eliminate the need to replace these front panel indicators within the foreseeable future.   You can see the result below for the 1580kHz stereo station-- also showing the AM stereo MPX indicator in the lower left corner of the LED tuning display:
    McIntosh front panel with white LED

    Tha Dood is going to button up the modification.   He says, "I hope to mount the meduci board, and I believe that I've finally found a decent place to do that, just between the Tuner Board and faceplate board is a dummy foot hole, with a plastic plug in it.  " As the pictures show, this was a very successful AM stereo conversion modification project.


    Mike G. from Hudsonville, Michigan USA successfully modified his Sony STR-DE525 receiver to hear WLS-AM (Chicago, Illinois USA) and WIRL-AM (Peoria, Illinois USA) in stereo at night!

    This picture shows the successful installation with AM_ST decoder mounted flat against the outside of the existing FM/AM tuner pack inside Mike's Sony STR-DE525 receiver:

    Sony AM stereo installation

    There were five total new connections made inside the Sony tuner pack.   This tuner pack uses the Sanyo LA1837 IC chip, which is an "AM stereo friendly" design, with easy left and right AM stereo audio connections back into the chip:

    Sony Connections It's a Sony

    Mike breaked the connection between pins 22 and 24 on the LA1837 to disable the mono AM audio path.   Also, this Sony receiver's micro-processor does not read the STEREO pin voltage level when the tuner is placed on AM medium wave band.   Therefore, the front panel stereo indicator did not properly indicate when AM stereo C-QuAM stations were received.   Mike was able to ingeniously use the receiver's front panel DVD/5.1 Dolby Surround LED indicator to indicate when this receiver was tuned to AM stereo stations.   This indicator now serves duty as AM stereo, DVD, and 5.1 Dolby Surround indication.   Mike made the connection on the printed circuit board behind the front panel:


    After this installation was completed, Mike says, "Well, Jeff I got her to work !!! You were right about the stereo indicator light only working during FM operation.   So found out that where I tapped the power it was dropping the voltage to about three volts so the decoder wouldn't work.   Tap it to the tuner power and works great now.   I used 15k-ohm series resistors for audio and sounds great.   ... I appreciate the product and help."

    Mike is procuring parts to assemble his own home-made large tunable loop antenna in order to improve reception further from distant AM stereo stations.


    Sanyo Boombox Mod

    Sean Cuthbert installed his meduci AM_ST decoder board inside the Sanyo M7850K AM/FM/SW/cassette boombox radio with very good results.   He found that second hand AM stereo radios are very expensive, as sold on eBay.   To save money, Sean decided to convert his own radio to AM stereo reception.   He likes this Sanyo model, as it has two shortwave reception bands.   In order to improve the recovered audio bandwidth, Sean also replaced the AM medium wave ceramic filter with a better device, capable of 10kHz audio response.   This compares to the stock ceramic filter that allowed the AM radio portion to reproduce audio up to 4kHz (essentially telephone line quality)! Also, an integrated cassette recorder facilitates AM stereo airchecks to be saved.

    playback button Play the video by clicking here>> AM stereo modification to Sanyo boombox.


    Neto Silva from Brazil installed his meduci AM_ST decoder into his J. C. Penney MCS-3050 tuner to improve the overall sound and to reduce audio distortion.   Why would anyone add an AM stereo decoder to a tuner that already contains an AM stereo tuner? J.C Penney uses the Motorola first generation AM stereo decoder chip (MC13020P).   In the third generation decoder chip (MC13028A) used in our AM_ST add-on board, a balanced full-wave envelope detector is used, which is technically better than the half-wave diode envelope detectors used in garden variety AM tuners and receivers.   This design improves audio fidelity, due to the very low total harmonic distortion encountered (typically under one percent, and inaudible to the human ear)!

    MCS3050_Upgrade MCS3050_Upgrade2

    There were six connections made from the AM_ST decoder board to the MCS-3050 tuner board. Of course, meduci provided complete and detailed installation instructions with Neto's AM_ST decoder module purchase! If you have MCS-3050 tuner, you should consider upgrading the AM stereo functionality with one of our AM_ST models.  


    decoder inside decoder outside

    Rich Modafferi built his "connect to any radio" AM stereo decoder enclosure to house his meduci AM_ST decoder board, which complements his tube-based AM stereo C-QuAM transmitter.   Rich also used his Sencore SG80 stereo generator for testing purposes.   His enclosure has inputs for 455 kHz I.F and a level control is provided for adjusting this I.F input.   There are both BNC and RCA I.F input jacks, and fixed and variable audio level outputs.   Single indicator lamp functions for "power" and "stereo", glowing dim on power, and full bright for AM C-QuAM stereo lock.



    X-FM conducted C-QuAM stereo broadcast on July 23, 2012.   Kenwood TS-140S shortwave receiver was modified by JFarley for AM stereo reception using his AM_ST decoder.   This modification allowed reception for this X-FM underground test broadcast from Redhat using C-QuAM stereo technology! This unique "music to the power of X" broadcast signed on just after 02:00 UTC with test tones at various frequencies, then X-FM identification as "C-QuAM AM stereo test transmission" followed by The Cars "Moving in Stereo" song.   Indeed, this is an appropriate song for this test! You can listen to this stereo broadcast here>> meduci AM STEREO SHORTWAVE TEST (20.2MB).

    XFM Test meduci close up

    There is some fading evident during the 43-meter single sideband shortwave test transmission.   As expected, lack of stereo lock occurred during the very deep fades.   From JFarley: "With the hardware decoder on a TS-140S, I have pilot about 50 percent of the time.   Thought there was separation during The Cars piece when you got above S9.   Kind of eerie listening and just getting a feel for this.   It's noisy tonight with choppy fades.   The meduci decoder in the TS-140S seems to lose pilot easily in a fade.   I am in and out of lock with fading, and it is sometimes a pronounced difference, sometimes it is more subtle.   But it is stereo! Reception here was around S8-S9, and that would have been enough to keep pilot lock here, I feel.   Problem was the very choppy fades down to S5.   I also noted some unlocking due to noise." If you want to find out when XFM is on the air, you may wish to check out the >> HF UNDERGROUND link here.

    You do not need to search high and low for a Kenwood TS-140S shortwave receiver.   Our past customers have successfully combined Redsun RP2100 with our outboard AM_ST stereo C-QuAM decoder board with very good results.   Redsun RP2100 is nearly identical to C.Crane CC Radio-SW model.   Both models tune the entire shortwave radio bands, and have the necessary 455kHz I.F output, so you do not need to open the radio, in order to install our AM_ST model C-QuAM decoder board.


    Todd's First!

    Todd Roberts (WD4NGG) converted his Delco automotive FM stereo/AM mono radio (model 16194955 - readily available on eBay) to AM stereo using his meduci outboard AM_ST decoder, so that he could hear "The Mighty 1630 KCJJ" in stereo. He also receives WLS from Chicago via skywave propagation! He added the forced mono switch to one of the mounting ears of the Delco radio! He placed the AM_ST board in a plastic box and added front-mounted AM Stereo indicator.   Todd also replaced the stock 3kHz ceramic filter in the Delco radio with new 7.5kHz ceramic filter from eBay.   This was a simple modification, since the 450 kHz I.F level from the Delco is an ideal match to the AM_ST board!

    Since muRata 3.6MHz ceramic resonators were as scarce as hen's teeth at the time, Todd used one 43uH toroid inductor resonated with a 9-50pFd ceramic trimmer in place of the stock ceramic resonator.   With continued experimentation, Todd says, "One thing I noticed using the toroid with loose turns wound over the core was it seemed to be a bit microphonic if bumped, so the turns will need to be glued in place, and the toroid probably glued to the board, to make it rock solid.   Of course there were no microphonics noticed when tapping the ceramic resonator."

    Todd's BUD Box

    Todd's most recent summer project was to relocate his meduci AM_ST outboard decoder into a small aluminum shielded BUD box enclosure, which was mounted to an aluminum sub-panel, then bolted to the front mounting ears on the top of his Delco 16194955 AM Mono/FM Stereo automotive radio.

    Todd's solution to interfacing the Delco's internal top tuning board to the outboard AM_ST decoder was to solder a printed circuit board-mounted SMA socket directly to the tuner board.   This socket was connected across the output pin from the 7.5kHz ceramic filter, and its ground pin, without having to drill any holes, or change anything on the tuner board.   Todd was then able to route the I.F signal from the Delco radio to his AM_ST decoder board using a small SMA shielded jumper cable and SMA connectors.   Todd did have to punch out one 0.5-inch hole in the top cover of the Delco radio, in order to allow the SMA socket to protude through the top cover.   Modifications were not necessary to the Delco tuner board itself, though.

    Using a spectrum analyzer, Todd determined that using this very short length of small SMA shielded cable did not affect the I.F filter's passband or ripple.   This re-packaged combination also eliminated the stray shortwave station interference that Todd had previously encountered, sometimes when listening at night, when using his AM_ST decoder mounted in an unshielded plastic box.

    Hopefully, these modifications provide inspiration for project creations using your own meduci AM_ST decoder board.   Please send us your AM stereo decoder conversion pictures, experiments, and descriptions using your AM_ST decoder! We will display the pictures and describe your project in an upcoming meduci web site update.

    History of AM Stereo

    Analog AM stereo technology has claimed its roots almost since the beginning of conventional monaural AM broadcasting within the United States.   Later, four different competing AM stereo systems were placed on the air in the early 1980's, including systems from Motorola (C-QuAM™), Magnavox (PMX), Kahn-Hazeltine (ISB), and Harris Broadcast (Variable Angle Compatible Phase Multiplex, or V-CPM).   Eventually in 1993, Motorola's C-QuAM technology achieved the exclusive standard for AM stereo broadcasting within the U.S.A. During this time period, Australia, Japan, and other countries were also exclusively using the Motorola C-QuAM system, making C-QuAM the essential de facto world standard for AM stereo broadcasting technology.


    All of the AM stereo systems share in common the addition of a stereo exciter to the existing monaural AM transmitter.   This exciter typically has two outputs: the monaural L+R audio, which is time delayed and fed to the transmitter's normal audio input; the second output is the R.F carrier, which replaces the signal from the transmitter's normal quartz crystal oscillator stage.   This signal also contains the necessary time delayed and phase modulated (quadrature) information.   Because these stereo exciters are retrofitted onto transmitters which were never designed for AM stereo operation, they also must contain corrective equalizers and adjustable delay networks, to insure that all of the relationships are correct through the transmitter modulator, power amplifier, and ATU/antenna system.   Decoded stereo separation suffers if the timing and phase relationships are not correct at the receiver.

    Motorola's C-QuAM system is covered in several U.S. patents written by the late Frank H. Hilbert and the late Norman W. Parker of Illinois. Norman Parker invented the C-QuAM system, per written correspondence from his wife, Margaret Parker.   Margaret also wrote all of the patents.   Patent number 4,218,586 was applicable to the basic system.   Several other patents included 4,406,922 and 4,192,968.   Delco Electronics Corporation (now known as Delphi) later introduced many adaptations and new C-QuAM inventions, covered under various additional U.S patents.

    About us

    meduci, LLC is a highly entrepreneurial, creative, and innovative research and development organization that specializes in custom free-lance engineering, research, electronic design, development, and production of electronic products, from conceptual ideas through to finalized products, in prototype quantities, up to large scale manufacturing.   We also design low frequency (class A, class AB, class D) audio power amplifiers, class C power R.F amplifiers, and R.F front-end (amplifier, mixer, oscillator), using National Semiconductor, Motorola, and other custom ASIC chipsets and discrete components.   We strive for quality and excellence in workmanship.   Our products are designed for faithful sonic reproduction of the on-air source material.   For customers with specific requirements, you could always count on us to produce innovative solutions in a time effective and cost efficient manner.   Our customers are benefited by better pricing, quality warranty, and excellent technical support.   Contact us for a free quotation -- we appreciate your business.   Our goal is to meet the needs of our buyers, distributors and dealers, and we can work on an ad hoc basis.

    . Please inquire for further details, and do not forget to mention "AM stereo" (without quotes) in the subject line to bypass our internal junk spam mail filters.   Write to amstereo'AT' (replace 'AT' with the @ sign).
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    13 March 2020

    Dear valued customer,

    meduci, LLC is diligently working to manage through this worldwide, daily evolving novel Coronavirus (COVID-19) emergency pandemic crisis situation that we all currently endure.   Pursuant to guidelines issued by the U.S Cybersecurity and Infrastructure Security Agency (CISA), and U.S Department of Homeland Security (DHS), meduci, LLC is part of the essential critical sector infrastructure, and is required to remain open for business as an essential service, to continue to receive raw components and supplies, to manufacture electronics products, and to ship these products to the end user sector.

    We continue to ship globally, with our highest priority being our internal and external customers.   We do not ship UPS Red Next Day service, nor any other expedited delivery service at this time.   Shipping guarantees are NOT being made from the carriers.   Refunds are also not being granted from these shipping carriers for delivery delays.   There is a huge increase in volume, as more people are shopping online, due to COVID-19 restrictions.   Unfortunately, this means your parcel delivery will be delayed.   For domestic shipments prior to 03/12/20, it would take a few days to one week for delivery.   These domestic deliveries are now taking weeks to complete.   For international shipments from USA, previously it would take weeks for delivery.   These deliveries are now taking months to complete.   This is being caused by limited domestic and international airline flights, significantly reduced airline capacity on those flights, local route restrictions, delivery controls, flight disruptions, flight cancellations, government restrictions, border closures, and increased safe distancing requirements.   Delivery companies are now operating with split shifts, ensuring clean disinfected work areas and stations between shifts.   Rest assured, that we are doing everything we can do to minimize order processing and delivery delays.   We will provide updates as they arrive, and we will continue to monitor the ongoing situation.

    Notice of Force Majeure-- meduci, LLC is fully operational to help with your end user product needs as an essential manufacturer, despite some of these recent world struggles.   We will inform you via e-mail the current status for your submitted orders to meduci, LLC.   We will also provide shipment tracking numbers when orders ship from our facility.   Some international delivery services are no longer available, due to COVID-19 response.   Thank you for your patience during this difficult time.

    We are keeping meduci, LLC members safe from the virus, with every possible preventative and protective measure put into place.   Out of an abundance of caution, and in adherence with guidance provided by local authorities, we have created policies to slow the virus spread internally within our organization.   We have limited travel, canceled meetings, restricted outside visitors, encouraged sick people to stay away, and have enhanced our cleaning and disinfection procedures in order to maintain a safe working environment.   Essential operational fulfillment and production support areas of the business continue under greatly enhanced procedures for sanitation, social spacing, and six-feet (1.828 meter) safe distance.

    30 May 2021

    We are experiencing challenges in procuring raw materials, due to the current global semiconductor device shortage.   Where devices were available, we were shocked to observe more than 70,000 pieces were purchased literally "almost overnight."   This through-hole device is now on backorder, until late 2022 from this semiconductor device manufacturer.   When it recently became time to re-order components again for the meduci MW-2A PLL tuner, the same trouble existed locating certain parts.   Half of them are still out of stock, some with a lead time up to 52 weeks.   These short supplies and delivery delays are causing the costs to rise for remaining available components, at double the previous prices.   Suppliers are passing these costs on to their customers, including significant Section 301 import tariffs, their increasing transportation costs, and their other costs for each purchase.   We held off raising our prices as long as possible; however, we wish to communicate at this time that our business is being impacted by these increasing operating, shipping, storage, and other costs.   We will continue to do our best to offer the MW-2A PLL tuner and AM_ST decoder, to try to avoid the inevitable "last call" lifetime buy for these two products.

    These tight operating challenges have directly affected our AM_ST decoder sales on eBay in 2021.   meduci made a business decision not to renew the eBay auctioning for AM_ST decoders, as it became cost prohibitive to maintain that listing every month.   We indeed chose to keep the $28.00 price point for each sale since the very beginning, with $25.00 best offer price, despite raw materials prices, and other costs, to increase year-over-year prior to the worldwide pandemic.   eBay also raised their rates many times, as well, during this long time period, and nearly 15-percent of gross sales proceeds were going to eBay listing fees, sales commission fees, state sales tax, credit card fees, and other up-front expenses- from each AM_ST decoder sale.   eBay sales, exposure, promotion, and visibility were also decreasing every month.   If AM_ST decoder sales resume again on eBay, these increasing costs will unfortunately need to be passed on to each new purchaser.   We continue to sell the AM_ST decoder via Buy Now PayPal direct purchase availability (link is above).   We never receive your credit card nor other financial information, and we maintain your privacy, by NOT selling address lists and your other personal information.   We also do not use tracking cookies on any of our web pages to harvest web site browsing and other information.

    25 August 2021

    All international shipping service was temporarily suspended on 25 August, 2021 due to impacts related to the COVID-19 pandemic and other unrelated service disruptions. This is an unfortunate circumstance. We will let you know when international shipping service is restored. Thank you for your understanding.

    Thank you for your continued support.   Stay healthy and safe.   We will all prevail to get through this difficult time period together.

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    This web page was updated on Sunday, October 10, 2021.

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