Greetings and Welcome to...

The AM STEREO Page

the FIRST of it's kind on the World Wide Web.

On this page, you will find info, links, thoughts, etc. on one of my absolute favorite pastimes:

This particular technology is what I refer to as "Ghostware".  That is, technology which is alive and well, but not many people really know or, often times, care about.  Many people think that just because you are listening to AM radio on two speakers, you are experiencing the broadcast in stereo. Not so. You need a special radio with an AM STEREO decoder chip in it in order to actually hear the broadcast in stereo.  All AM stations which choose to broadcast in stereo today do so by using the Motorola C-QUAM (Compatible QUadrature Amplitude Modulation) system.  Here's the little unit (called a C-QUAM exciter) which makes it all possible:

The Motorola C-QUAM AM STEREO system operates in a classic manner, with the L+R amplitude modulating the carrier to the maximum of 1.0 radians, for 100% L-R.  In the receiver, this information is recovered by conventional amplitude and phase detection methods, and added algebraically to the resulting L and R information.  The math is:

(L+R) + (L-R) = 2L; (L+R) - (L-R) = 2R 

As for me, I have been an enthusiast of AM radio all my life (partly due to the fact that there were no "real" FM stations in existence in my neck of the woods when I was growing up).  Even as a kid though, I remember thinking to myself, "Why do AM stations not broadcast in stereo?" Needless to say that in the early 80's when AM STEREO was first introduced on a wide scale, I was elated.

Around 1983, SONY came out with their now vintage SRF-A100 AM STEREO/FM STEREO personal radio as well as the SRF-A1 AM STEREO/FM STEREO Walkman.  (At this time, there were four competing AM STEREO transmission standards in existence:  Harris, Kahn/Hazeltine, Magnavox, and Motorola C-QUAM, with an A/B switch on these particular radios to choose the correct type of transmission standard for the station you were listening to: "A" for Harris, Magnavox, and Motorola C-QUAM; "B" for Kahn/Hazeltine)  However, I could not justify spending the money to buy one of these new little gadgets (although I desperately wanted one) and figured that if I just held on, the price would eventually come down and I would be in my glory.  Little did I realize that in would soon be easier to find a needle in a haystack then it would to be find either of these units.  In early 1998, after 14 long years, I had the good fortune to finally add the SRF-A1 Walkman to my collection thanks to a extremely generous donation from a radio collector.  I guess good things really do come to those who wait, as later in 1998, I was finally able to add the coveted SONY SRF-A100 to my collection.  Believe me, it was like all those years hadn't even passed by.

Pictured above is a display ad for the AMazin' AM STEREO campaign that SONY ran in Canada back in the mid-80's promoting their complete line of AM STEREO products at that time.  Look closely and you can see the SRF-A1 Walkman, SRF-A100 radio, CFS-6000 boombox, ST-JX220A and ST-JX520A home tuners, various STR-AV series receivers, WM-F16 Walkman with cassette and XR-A series car radios.  Please note that many of the above products were only sold in Canada and Australia and were never introduced to the American marketplace.

As for me, I remember vividly the very first time I heard an AM station broadcasting in stereo.  In fact, I remember it like it was yesterday:  It was in a brand new, fully loaded 1985 Buick LeSabre Limited Edition with a factory GM/Delco AM STEREO/FM STEREO radio, complete with auto-reverse cassette, 5 band EQ, and the coveted "AM ST" button.  The station was 1270 CJCB in Sydney, Nova Scotia and the sound completely blew my mind.  I could not believe that I was actually listening to an AM station and it was really strange to see the "STEREO" indicator light on.  Sadly, CJCB no longer broadcasts in stereo, despite the fact they still have a music format.  (Due to a format change on June 29, 1998 they are now known as Cape Breton's Country Favorites, 1270 CJCB).  For the record, CJCB was also the first AM STEREO station I ever heard on my SONY SRF-42 Walkman in 1995.

The above is a picture of CJCB's "Sunspot".  This one was issued in 1989 to commemorate their 60th Anniversary on the air.


AM STEREO Capable Radios

It is interesting to note that on page 71 of the 1996 Canadian Radio Shack catalogue, the Questions & Answers box reads:

Q.  How can a radio with one speaker, like some of the portables shown in this catalogue, still produce stereo sound?  

A.  These radios receive the radio frequency signal in the manner it was sent, either stereo, like most stations, or in mono, which many AM stations still broadcast in.  Then, because it only has one speaker, it re-broadcasts the both left and right channels in mono.  However, the signal is re-broadcast in stereo once stereo headphones or earphones are plugged in.

I'm sure everyone would agree that this sounds like an accurate explanation, except for the fact that Radio Shack does not sell AM STEREO units in Canada.  If you ask one of the Sales Associates if a particular radio has AM STEREO capability, the most common reply is, "They all do."  My other favorite reply is, "Why would you want to have something like that?", to which I happily reply, "Why would you want to wear a tie like that with those pants."  (Feel free to use this line the next time you're in Radio Shack and feel like causing trouble.)

Back in the 1980's and even into the early 1990's, however, there were some radios available for sale in North America which were capable of receiving AM STEREO broadcasts.  I have compiled a list (in alphabetical order) based on discussions I have had with various people about such radios.

To view this listing of AM STEREO capable radios (along with some color photos), either:

(For those wondering , this particular unit is available for sale in North America, however it must first be converted to enable you to receive AM STEREO broadcasts.) 


My Personal AM STEREO Radio Collection

I am the proud owner of the following AM STEREO radios which, to me, are worth considerably more than their weight in gold:


What Happened?

There are a number of reasons why AM STEREO radios are so difficult to come by or are nowadays non-existent.  In a nutshell, what killed the availability of such radios was a Lack of Standardized Technology.  That is, back in March of 1982 when the FCC authorized AM stations to begin broadcasting in stereo, there were four competing AM STEREO transmission standards and different stations broadcasting with each.  As a result, radio manufacturers were hesitant to spend time and money to design and build radios which were capable of only receiving one type of AM STEREO transmission.  Why spend money on such an endeavour only to find out that the particular transmission type a company had chosen to "endorse" would not be the final one?  This would only make the manufacturer's product essentially useless; that is, you would end up owning a radio which would still allow you to receive AM broadcasts, but not allow you to ultimately receive the broadcast in stereo.  (The FCC in the United States opted to adopt a "laissez-faire" approach to this problem which didn't help matters either.)

One way around this "foolishness" was to use multi-synchronous type AM STEREO decoder chips in AM radios which would allow a listener to receive the broadcast in stereo regardless of what type of transmission system was being used by the station you were listening to.  In Canada around 1988, the Federal Department of Communications passed legislation stating that any AM station wishing to continue broadcasting in stereo would have to do so using the Motorola C-QUAM method.  The FCC still continued to drag it's feet on this issue, thus causing manufacturers to still be hesitant towards production of AM STEREO radios.  A cat and mouse game?  A vicious circle? Call it what you will, but one thing remains clear:  actions such as these effectively contributed to the so-called "death" of AM STEREO - a technology that was once thought to be the "savior of AM radio" and one which had the ability to make unsuspecting listeners think that they were actually listening to an FM STEREO broadcast.  Still into the early 90's, Motorola and Kahn/Hazeltine were locked in a vicious legal battle to finally determine which would be the AM STEREO standard in the United States.  In the end, Motorola may have won the war, but the battle, so it seems, was lost.


Is There Any Hope?

Recently, the NAB has endorsed a new type of "quality control" for AM STEREO broadcasters known as AMAX AM STEREO.  AMAX (AM at its MAXimum) is basically a standard that has been developed between the industry associations and the Motorola corporation.  In order to advertise that the station is broadcasting in AMAX AM STEREO, it must make the necessary improvements in playback and transmission equipment so as to meet the AMAX quality standard.  For manufacturers of AM STEREO receivers, a similar requirement has been established in that their receiver must meet certain technical criteria with respect to performance in order for the receiver to be permitted to bear the AMAX logo.  Specifically, a tuner or receiver must have frequency response from at least 50Hz to 7.5 kHz with correct NRSC de-emphasis, automatic noise blanking to reduce impulse noise, manually or automatically selectable audio bandwidth, connections for an external AM antenna, and the capacity to pick up all stations on the extended AM band (i.e., up to 1710 kHz).  The only two home or personal radios that were made available to North American consumers which are AMAX-certified are the limited production Denon TU-680NAB home tuner (the first to incorporate all of the AMAX requirements) and the SONY SRF-42 Walkman.  Both have an AMAX logo on the front of them.  As well, there does seem to be some corporate interest in the production and distribution of new AM STEREO radios for the North American market.  Whether or not they will be AMAX-certified is uncertain at this time.  Encouragingly, the Japan Radio Company (JRC) has officially unveiled its NRD-545 DSP AM STEREO home receiver with a MSRP of $2000.00 US.  Besides these units, there are several AM STEREO capable radios currently available in Japan which allow you to "switch them" out of the Japanese domestic frequency bandplan (i.e., 9 KHz tuning steps) for use in other parts of the world:

In addition to the above SRF-SX100RV, SONY of  Japan also produces the following AM STEREO products which are compatible with the AM North American 10 kHz bandplan. The only problem is that they are only available in Japan:


AM STEREO Industry Update from Chrysler Corporation

According to Chrysler Corp.'s various web sites, the vast majority of the 1998 Plymouth, Chrysler, Jeep, and Dodge cars and trucks can be equipped with an AM STEREO radio.  Some models even have AM STEREO as standard equipment.

According to their web sites, Chrysler has three different types of AM STEREO-capable radios currently available which plainly say "AM STEREO/FM STEREO" when describing these units.

The most popular radio has both cassette and CD players built-in, along with a 3-band graphic equalizer and a balance/fader joystick. This radio (known as the RAZ) uses either blue or orange illumination, depending on the type of car it's in.  To aid in your search, here's a picture taken out of a 1997 Dodge Dakota truck.  (Notice that the radio is tuned to 1560 WQEW AM STEREO. Obviously, this photo has become of some historical significance.)

Next, there is a "rounded-off" version of the above radio, found only in the Chrysler LHS, 300M, and Concorde.  It's functionally the same, but the knobs and dials have been rounded off to fit better in the curvy dashboard.  This radio has blue illumination.

Finally, there's a cassette-only version (i.e., no CD player), with 5-band graphic equalizer and balance/fader joystick.  This radio is only found in the Chrysler Town & Country Minivan, and has blue illumination.

As you may have noticed, these all are high-end radios.  As previously mentioned, Chrysler has not put AM Stereo in their base-model radios since 1992 when they decided to stop including this option as factory standard on all of their vehicles.  After a year with another supplier for their radios, in 1994 they started putting AM STEREO only in high-end equipment.  The injustice here is that AM STEREO fans are now forced to pay up to get what they crave!  Here's a shining example of this:

If you're considering purchasing a 1998 Dodge Neon, the only AM STEREO radio available is the RAZ model with CD and cassette as described above.  However, for the Neon, it's NOT available factory-installed, but rather only as a dealer-installed option.  This particular radio needs at least the 4 if not the 6 speakers installed at the factory to work.  Essentially this means you have to buy the car with a "premium" sound system from the factory ($395.00 US MSRP) and then have the dealer install the RAZ radio ($625.00 US MSRP) with NO allowance given for the radio being removed!!  Obviously, they're not selling too many that way.  There are some Chrysler products which offer the RAZ factory installed with 6 or 8 speakers for $595.00 US MSRP, and that's less than the same radio without speakers for the Neon!  Rather hard to understand isn't it?

AM STEREO Industry Update from Ford Motor Company

While the specifics are sketchy, virtually all Ford car radios now have AM STEREO.  (The Taurus/Sable oval radio is included as well.)  In fact, the new cassette/CD/radio in the Ford Explorer not only has AM STEREO, but also has radio information services on FM (i.e., FM RDS).  While there are no apparent AM STEREO markings on Ford's factory radios, if the vehicle has a Premium Sound system (which is clearly marked on the unit), you can be pretty sure it has AM STEREO.  Beyond this, I'm told that Ford plans on continuing AM STEREO support in its vehicles for the foreseeable future.

Coming soon:  An AM STEREO Industry Update for GM cars and trucks.


AM STEREO Radio Stations

For a listing of stations broadcasting in AM STEREO in Canada, the United States, Mexico, Australia and elsewhere, please click here.


Did You Know...

No other countries rely so heavily on the AM radio band as do Canada and the United States? Talk Radio is considered to be the most important communication medium as well as the most popular format on AM in these two countries.  In Canada, Oldies and Country formats also do particularly well on AM.  

All of AIWA's home audio shelf stereos (i.e., "bookcases") that were made until 1996 were equipped with the circuit board required to support AM STEREO?  The only thing, however, was that they left out the AM STEREO decoder chips on the North American models while only the Japanese market units with the D and HD after the model number were made with the parts installed.  AIWA still makes a complete line of AM STEREO capable units, but only for the Japanese market.  Again, these models have a D or HD after the model number.  Interestingly, all of the new North American AIWA products that come equipped with tuners have the AM STEREO area on the boards again, but with the decoder circuitry missing.  (These products were manufactured in 1998.)  The 1997 North American units did not have the boards that were AM STEREO ready, but these can still be converted if you have the technical savvy to do so.

You can easily adapt the SONY 2010 shortwave radio for AM STEREO?  This unit, and all the other SONY's that use multi-synchronous detection, uses the SONY chipset in the Harris mode to do their synchronous detection.  You can simply attach a stereo line-out jack to the 2010 (or SW-100, or SW-77, or ICF 2002) and hook it to the output of the stereo chip.  Then, simply plug into a stereo amplifier and, Presto!  You now have a radio capable of receiving Motorola C-QUAM AM STEREO broadcasts!  For further details, please click here.

Most Chrysler car radios can be modified for AM STEREO?  They carry the C-QUAM decoder chip, but some of the external components are missing.  The envelope detector in the chip is of the synchronous type, therefore you will experience an improvement in reception.  You do have to be a bit skilled to make the transition, but as a starting point you can obtain the data sheets and recommended circuit hook-up from the Motorola website, and then simply trace the foils to find out what exactly needs to be added.

On some of the AM STEREO receivers that use standard Murata ceramic IF filters, you can easily open up their bandwidth by replacing the standard filter with a wider one?  Murata makes them in all sorts of sizes and bandwidths.  The same is true for car radios.  Once the IF is opened up, you are able to turn a good sounding AM STEREO into a marvelous sounding one.

On September 24, 1975, The National AM STEREOPHONIC Radio Committee (NAMSRC) was formed to test the proposed AM STEREO transmission systems?  NAMSRC was jointly sponsored by the Electronic Industries Association (EIA), the National Association of Broadcasters (NAB), the National Radio Broadcasters Association (NRBA), and the Broadcasting Cable and Electronics Society of Electrical and Electronics Engineers (BCCE).

In 1980, the Magnavox AM STEREO transmission system was actually chosen by the FCC as the standard system for AM stations who wished to broadcast in stereo?  This decision was eventually overturned by the FCC after heavy lobbying by the other competitors who were in the running to get their system chosen as the "technologically superior one".

There was actually a fifth AM STEREO transmission standard at one time?  It was the RCA-Belar system, which was first exclusively tested by RCA in 1959 and developed at Belar Electronics Laboratory, Inc.  As a result of the aforementioned decision of the FCC regarding the selection of a transmission standard, and sheer disgust, RCA-Belar voluntarily dropped out of "the AM STEREO race" in 1980.

Philco also developed an experimental AM STEREO system in late 1950's using quadrature modulation and tested it on 770 WABC in New York, NY?  They actually proposed their system to the FCC, but the Commission rejected all AM STEREO systems at that time.  

Westinghouse also developed their own AM STEREO system in the late 1950's?  At the time, Westinghouse was preparing to test their AM STEREO system on station 1020 KDKA in Pittsburg, PA.  It is unclear, however,  if these tests were ever carried out or not.

CBS also tried out a very similar system and conducted experimental transmission on 880 WCBS in New York, NY in the early 1960's?  CBS, however, did not pursue its system further.  The ironic thing is that the FCC at that time granted stereo capabilities only to FM radio, which was having difficulty competing with AM radio!

The Canadian Broadcasting Corporation (CBC) tested all four AM STEREO transmission systems on their 50,000 watt station 1250 CBOF in Ottawa, Ontario in the mid-80's?  Sadly, when the Motorola C-QUAM system was chosen as the standard in Canada in 1988, CBC discontinued stereo operation altogether on 1250 CBOF.  (CBOF ended up defecting to the FM band at 90.7 with the same calls on January 7, 1991 and their new output became 84,000 watts. After a brief period of simulcasting, CBOF AM was shut down for good on March 26, 1991.)

The National Semiconductors LM1981 was the first AM STEREO integrated decoder chip introduced in October of 1980?  This particular IC was designed for receiving the Magnavox AM/PM system, but also had the ability decode the Motorola, Kahn /Hazeltine and Harris systems.

The first AM STEREO integrated decoder chip designed by Motorola was introduced in 1982? It was the MC13020 and became the industry standard for such IC's for a long time.  Other Motorola IC's are the MC13022, MC13024, and MC13028.  

The new Motorola MC13122 C-QUAM IC in conjunction with the MC13027 noise blanker is what makes a receiver AMAX AM STEREO certified?  

SONY made their own IC's, but it required 2 chips to do what one Motorola integrated chip could do?

Toshiba also makes two AM STEREO integrated decoder chips?  It's earlier model # is TA8124, while the new IC is model # TA2040.  The former can be used in both analog and digital tuning radios, while the latter can only be used in digitally tuned units.  FYI, Yamaha and Kenwood use the TA2040 in their Japanese AM STEREO products, and all AIWA boards are plated for their use.

Sanyo manufactured their own multi-mode AM STEREO decoder?  It's model # was LA-1910 and the NTIA committee found that multi-mode receivers that used this chip, "worked very well and decoded both the Motorola C-QUAM and Kahn/Hazeltine systems with excellent quality and low distortion".

In late 1984, CHRYSLER became the first North American car manufacturer to make AM STEREO radios standard equipment on their 1985 line of automobiles?  (At this time they used the Motorola MC13020 IC in their factory radios.)   It has been officially confirmed to me that the following two Chrysler car radio models have AM STEREO:  4469106 (tuner and cassette) and 4469075 (tuner only).  (Note: Model # 5269411 (tuner only) does NOT have AM STEREO.)  As pointed out to me, perhaps the "446" prefix signifies it is an AM STEREO capable unit.

On Monday, December 17, 1984 the Broadcast Group of Harris Corp. announced a licensing agreement with Motorola, Inc. to manufacture and market AM STEREO exciters and monitors using Motorola's C-QUAM system?  Type acceptance for the Harris STX-1B C-QUAM AM STEREO Exciter had already been filed with the FCC at that time and prompt approval followed. Also at that time, current Harris users (which numbered some 200) were offered C-QUAM exciter modification kits and modulation monitor programs.  Harris estimated that if all of its stations made the conversion to C-QUAM, almost 400 AM STEREO stations would be on the air from coast to coast utilizing the Motorola system.

Motorola had a C-QUAM mailing list in the 1980's?  The C-QUAM Newsletter was put out by the marketing people at Motorola's AM STEREO Division in Schaumberg, Illinois and was meant to give information to people in the broadcasting industry and a track on what was developing about their system around the world.  (i.e., station lists, manufacturers of AM STEREO consumer equipment, and the status on circuit and IC revisions regarding their semiconductors and exciters)

The Official Birth of AM STEREO took place in Australia on Friday, February 1, 1985?  On that date, Mr. Michael Duffy, The Minister for Communications, officially launched AM STEREO in Melbourne.  The Australian DOC selected the MOTOROLA C-QUAM system as the standard to be used.  As well, Australian AM radio broadcasters banded together under the title "STEREO AM Australia" and launched an aggressive promotional campaign for AM STEREO with their official slogan being "I've Got The Best Thing Between My Ears!  STEREO AM"  (An excellent slogan, I must say!)  Prior to this, the majority of capital city AM stations in Australia had been broadcasting in stereo under a testing program sanctioned by Department of Communications with a proviso that no mention of this fact was to be made to listeners until after the official launch day. 

According to the official Gazette of Brazil, published on January 30, 1986, the Minister of Communications established by ordinance 22/86 the MOTOROLA C-QUAM system as the exclusive AM STEREO system to be used in Brazil?  At this time, Brazil joined Australia as only the second country to officially select the C-QUAM system as it's national standard.  

According to the FCC, 24 million (yes, 24,000,000!) AM STEREO radios were sold in the U.S. by 1993?  ( This figure does not take into account those radios which were sold in Canada up to that point.)   The FCC also claims that that there were 23 different manufacturers making AM STEREO radios in 1993.

The use of the use of the registered trademark C-QUAM is available at no charge to those companies which have a license from Motorola for the use of their C-QUAM technology?  This invites the use of the trademark on products which will make it crystal clear which radio has AM STEREO and which doesn't.  Therefore, if a receiver manufacturer has a C-QUAM technology license, they can now obtain a trademark license as well.  Precise labelling such as this would certainly go a long way in reducing/eliminating the confusion/misinformation surrounding AM STEREO for sure.    

Sixty-seven new AM STEREO stations are coming on the air in North America within the next 12 months?  As well, all US expanded band stations are required to meet FCC "Model I" criteria, which includes broadcasting in Motorola C-QUAM AM STEREO.

When a station begins to broadcast on an expanded band frequency that it can simulcast on its original frequency for up to five years?  After this time, the FCC requires the station to either continue broadcasting on their original frequency and drop the expanded band frequency, or keep the expanded band frequency and drop the original.

Most mid 80's and early 90's digital radios won't tune beyond 1620 on the AM band?  However, most (over 50%) analog AM radios will allow you tune in the expanded band, and ANY Shortwave Radio will tune DOWN to include the expanded band.

There is a company here outside of Halifax (Hackett's Cove, NS to be precise) that manufactures high powered broadcast equipment for radio stations?  The company's name is NAUTEL and they've been around since 1969.  (They also have a subsidiary US manufacturing plant located in Bangor, ME.)  For AM stations, they manufacture radio broadcast transmitters up to 60kW which have a built-in AM STEREO generator (Motorola licensed) included on request.  They also have AM transmitters capable off 200kW and are in line for higher powers in the future.  Their products are supplied to radio stations all over the world and all of the Halifax AM stations use NAUTEL transmitters.

The Harris DX-10 AM transmitter comes with C-QUAM broadcast capability as standard equipment, especially since it is a favorite of many of the new EB stations?  Beyond this, Broadcast Electronics has AM STEREO broadcast capability as a standard feature on all their AM transmitters.  Finally, Delta Electronics offers a complete line of AM STEREO exciters and monitors on their web site.

1510 WJKN AM STEREO in Jackson, MI (who actually promote the fact they are an AM STEREO operation) boast as being America's First All-Digital AM STEREO Station?   This statement refers to the music-on-hard drive system they use.  Beyond this, WJKN is attempting to build a modern, All Local, Full-Service station.  To help, they built their new digital studios at a local mall, making it a very accessible station to the public.  (Unfortunately, WJKN is currently sending out the 25 Hz pilot tone only due to problems with their digital STL.  Hopefully they will have this unfortunate problem resolved ASAP.)

The AM STEREO Page received a blurb on 1600 WWRL AM STEREO, New York, NY, during PM Drive with Gerry D. on Wednesday, June 3, 1998?    

The AM STEREO Page also received a blurb in the September 2, 1998 edition of  Radio World?  Specifically, it was mentioned in an article entitled, "AM Stereo and Its True Believers: A Crop of Die-Hard Fans Use the Internet To Promote the Benefits of AM Stereo" on pp.18-20. To view a scanned reproduction of this article from Chuck Simpson's web page, please click here.

The AM STEREO Page received another blurb in the January 2000 issue of  Popular Communications?  Specifically, it was mentioned in Bruce Conti's "Broadcast DXing" column on page 47 under the sub-heading "AM Stereo Enthusiasts".

There are three neat "tricks" to improve the reception of your AM radio?

According to Kevin Tekel, "Find a wall light switch in your house, with a non-metal faceplate covering it.  Attach a wire to one of the two metal screws holding the faceplate on.  Connect this wire to the antenna input of your radio, and now you have a very good antenna.  I have no idea why it works, but it does.  My "super antenna" trick also works for Walkman-type units as well. Take the end of the wire coming from the light switch and wrap it a few times around the Walkman, over where the internal antenna is.  On the SONY SRF-42, the internal antenna is just below the tuning dial. I tried this and reception dramatically improved!"

Chris Cuff adds, "What you are doing is using the grounded (safe) part of your home electric system as an antenna.  Myself, the absolute best antenna I have ever found was to simply wrap the cord of your telephone coming from the wall several times loosely around the radio. Amazing!"

Werner Funkenhauser also says, "Very often, just wrapping a few turns of wire about the radio, and clipping the loose end to a metal screw on the phone will also do the trick. Or, if there isn't a phone handy, use the ground screw on the electrical wall socket."  A word of caution however: A direct connection to the radio in a home that has old wiring, or some kind of ground fault, might be unsafe to the radio, or to the user, or both.


AM STEREO:  It Does Sound Better

There is no limitation to the fidelity of AM radio.  From a mathematical standpoint, AM does better in frequency response than FM.

- Leonard Kahn, 1982

Anyone who appreciates the sound that AM STEREO has to offer will know exactly what the above statement means.  For those of you who have never actually experienced an AM STEREO broadcast, you will absolutely amazed at the sound it is capable of producing.  I am telling you, if you did not know the difference, you would swear you were listening to an FM STEREO broadcast.  For those of us who have developed "trained ears", FM STEREO can't hold a candle to AM STEREO; the latter does not only blow the former out, it totally blows it away.

Why?  Well, the answer is probably better explained by focusing on the "how" aspect of this question.  Cris Alexander, Director of Engineering for the Crawford Broadcasting Company sums it up quite nicely:

"The main difference between AM STEREO and FM STEREO is that in AM STEREO, the sum and difference channels take different paths through the transmitter, as opposed to FM, where both go into a composite baseband which goes through the transmitter in a single path.  The WHY of the better sound of AM STEREO lies in the processing.  In FM, we limit, compress and clip the left and right channels individually in order to create the maximum RMS (i.e., apparent loudness).  Since in FM STEREO, 100% left or 100% right equals 100% modulation, this works just fine.  (This does not take into account the 9% that we must leave for the pilot (SCA modulation can run the baseband over 100% modulation), but it illustrates the point.)  In AM STEREO, however, 50% left plus 50% right equals 100% L+R, and the L+R is the mono sum that most of the listeners hear.  Lose the left or lose the right and there goes half your modulation and half your apparent loudness.  So in AM STEREO, we don't process left and right individually - we process L+R and L-R instead.  That way when, say, one channel is low or gone, it pumps the L+R in the main channel so that the mono listeners don't notice a decrease in loudness. Since we also process L-R (the difference between the channels or "separation"), we can increase the RMS of the difference and increase the apparent separation by several dB.  More precisely, in AM STEREO, since we must run the L+R and L-R through two separate paths, if we used conventional left and right processing, we would have to process symmetrically (i.e., at a level where 100% limiting will occur when L=R for the L+R and L=(-R) for the L-R path.) If we modulate with only one channel (left or right), we would take a 6 dB loss in both monaural loudness and coverage.  Instead, we process the L+R and L-R separately, so that when we do have single channel program material, the L+R envelope is "pushed" to 100% (we actually limit this to 90-95% as a result of real-world decoder limitations).  To a stereo listener, the single channel is actually 6 dB louder than it should be, but this is considered an acceptable trade-off when the alternative is losing 6 dB of the monaural modulation to which almost all the audience is listening.  (Also, John Byrns adds, "With FM STEREO, a full left only or right only signal will produce only 50% mono, which can't be increased to 100% with processing, as it can in AM stereo, to recover the 6 dB loss the monophonic listener experiences under that condition.")  So, there you have it.  That's why AM STEREO seems to have more separation than FM STEREO. You're right - it DOES sound better.  I've thought about processing L+R and L-R on our FM stations ahead of the main processor to see if I can achieve the same effect.  Bet I can."

Regarding the apparent increased separation with AM STEREO discussed above, Ken Pasolli offers,

"There really is no separation increase when you increase the L-R level relative to the L+R level.  There is an increase in "ambience" resulting from the increased L-R.  It's something I really don't care for. Our station does not artificially increase the L-R level and I find the signal cleaner and more listenable.  But as you know, audio processing is a pretty touchy subject among radio engineers!"

Regarding the NRSC Pre-Emphasis Curve, Ken Pasolli passes along this information:

"Most AM stations these days broadcast using a modified 75usec pre-emphasis curve. Some of the older wideband AM STEREO units do not have the proper de-emphasis, thus making them sound excessively 'bright".  The de-emphasis curve works out to be an approximate 10 dB cut at 10 KHz.  This is fairly easy to add to the older units, or can be approximated by the tone controls on a receiver or amplifier."

It's indeed true that many people prefer the sound of AM STEREO over that of FM STEREO simply because it sounds more natural and less over-compressed.  There's a good reason for this, and from the listener's standpoint, fellow AM STEREO fanatic Kevin Tekel provides the following explanation why:

"Even though frequencies above 10 KHz in the audio spectrum are mostly harmonics and other "noise", audio in this range carries a lot of "energy" with it.  You can verify this by transmitting in either AM or FM.  Specifically, by reducing the high treble sounds, you can transmit at higher modulation levels than if you transmitted full-bandwidth audio.  The high treble is what makes the distortion when you over-modulate; with the high treble reduced or eliminated, you can run higher modulation without distortion.

But things get even worse when you boost or pre-emphasize these high treble audio frequencies (as required by the FCC on the FM band).  As a result, you have to find some way to use the pre-emphasis while still keeping your modulation and signal RF bandwidth within acceptable limits.  The solution is to use "multi-band" audio processing and compression.  This way, the bass, mid-range and treble audio content is separately processed and compressed for maximum modulation in those frequency ranges. Consequently, the high treble has to be processed and "squished down" a great deal in order to keep the pre-emphasis and still remain within FCC-regulated bandwidth and modulation limits.  (The bass and mid-range is not subjected to such aggressive processing because it carries less "energy".)

AM radio of course also uses pre-emphasis, but with the 10.2 KHz NRSC cut-off, you don't have to deal with these high treble frequencies.  That way with the narrower bandwidth (only 10 KHz instead of 15 KHz) you can run higher modulation without resorting to large amounts of audio processing and compression.  In fact, some AM stations don't even use multi-band processing and compression *at all*, because it's not as necessary as when broadcasting on FM .  (This is called running "flat" audio, even when pre-emphasis is used.)

The result of this is that while FM has a more crisp sound due to the wider frequency response, the high treble frequencies above 10 KHz are "squished down" so much that it gives the overall audio an "over-compressed" and "artificial" sound.  The only solution is to back down on the modulation level so that you can use less audio compression and still fit within the FCC limits with the pre-emphasis.  But of course since all FM stations want to sound "loud" and "powerful" there is no way they are going to do this.  This is also why FM stations that play Classical music always sound better, because the music is usually nowhere near its full intensity, and therefore less processing and compression of the audio is being used.

In comparison, AM has a "cleaner" and "more natural" sound than FM since the 10 KHz cut-off lets you run full modulation and pre-emphasis without resorting to large amounts of audio processing and compression.  And most people don't notice the loss of high treble audio above 10 KHz, especially after they've been listening for a while; if you switch back and forth, you can tell the difference between 10 KHz-bandwidth and 15 KHz-bandwidth audio, but after you listen for a while you don't hear that anything is "missing".

In the real world there are many other differences between AM and FM that can be addressed, but in this case I am only talking about "closed-loop" observations of the differences between the two, as you would have when comparing the output of AM STEREO and FM STEREO transmitters at very close range, without regard to what happens when you receive the signal dozen or even hundreds of miles (or kilometers) away from the transmitter."

With all the above in mind, some people get upset that many Talk stations insist on sending out a stereo signal from their transmitters while only sending out a mono feed from their board.  William J. Wertz of the Fairfield Broadcasting Company in Kalamazoo, MI wishes to defend this position officially for anyone who might be interested in the "Why?" of it:

"The chip used on your receiver that picks up AM STEREO and carries it out to your speakers does a VERY important function in that it does more than create stereo; it's most important job is to open the bandwidth of the AM radio to a full 10 kilohertz.  This is critically important to any AM station and especially for a News/Talk formatted station. Your mono received AM radio has somebody talking to you out of 'that tiny speaker' and it sounds like it; the AM STEREO chip, however, opens the bandwidth and now that somebody talking to you sounds like they are sitting next to you and having a one-on-one conversation with you!  I can't emphasize the importance of that to the listener and, ultimately, to the radio station.  This is why I cut my hair so short; otherwise, I'd have pulled it out long ago due to the unbelievable short-sighted peers in our business."

Still not convinced?  Well, the best advice I can offer to any disbelievers is to get your hands on an AM STEREO receiver and then make sure you're strapped in 'cause you will be totally blown away.


"Offenders of The Faith"

Despite the above, there are still some AM stations who seem to think they sounded better in mono than they did when they were in stereo.  To see a list of these stations who possess a flaw in their logic, please see the following listings:


Technical Tidbits


The Kahn POWER-side Expander

The Kahn POWER-side Expander is a type of modulation technology which was developed by Kahn/Hazeltine Independent Side Band AM STEREO guru Leonard Kahn .  Basically, it's purpose is to improve the transmission of signals by broadcasters and the subsequent reception of those signals by listeners.  Here's how it works:  a normal AM transmission has a carrier and two sidebands: a lower and an upper one; AM single sideband (SSB) transmission, on the other hand, has a carrier and only one sideband.  The POWER-side is a cross breed of the two.  Specifically, it provides a broadcaster with some of the advantages of  SSB (i.e., less interference and greater range) with a compatible system for a normal AM receiver.  As a result, an upgrade of equipment is not required by the AM listener.  The POWER-side can also help in situations where one station is closer to another station on the AM dial and would like to minimize interference from the other.  By putting most of the modulation of the station into the sideband that is furthest from the interfering station, the signal will (hopefully) arrive cleaner on the listener's AM receiver.

Recently, I was asked if I could address on The AM STEREO Page how Kahn POWER-side Expander technology works to de-null the nulls in an AM pattern and how it precludes a station from broadcasting in Motorola C-QUAM AM STEREO.  Upon contacting Cris Alexander regarding this, here is the answer to the question:

"The Kahn POWER-side and C-QUAM are mutually exclusive.  Using the Kahn unit precludes C-QUAM, as it supplies the RF drive to the transmitter just as a C-QUAM exciter.  There are some situations where a POWER-side has made a big difference in a station's coverage, particularly in the null areas of a tight (and poorly designed) directional array.  In many other situations, however, the unit does nothing beneficial.  Essentially, the situation has to be evaluated on a case-by-case basis."

Ed Dulaney, CE of Crawford Broadcasting Company's Colorado state stations (560 KLZ, 670 KLTT, 800 KLDC, 1040 KCBR, 1220 KLVZ and 1530 KCMN which are all AM STEREO) goes on to say:

"The POWER-side does help in the null areas, however there are very bad side effects.  The most annoying is the extreme distortion of the signal when received on a standard envelope detector. Diodes aren't known for their linear qualities, and feeding them a non-linear signal tends to cause ample distortion of the output waveform.  However, on a synchronous detector, the station sounds wonderful."

"One good use for the POWER-side would be on Short Wave stations.  I think it would really decrease the obnoxious noises related to selective fading that are prevalent on the Short Wave band."

Gary Blau, CE of KISO AM/KOOL FM in Phoenix, Arizona adds:

"The POWER-side system is a modified Kahn AM STEREO exciter which is adjusted to purposely offset the modulation energy into one sideband or the other while still retaining reasonable distortion performance on typical mono envelope detectors.  The system is used without the pilot tone being transmitted, at least it shouldn't be.  It would cause 'weird' results on a C-QUAM receiver as it is not a stereo transmission scheme."

"The Flatterer is another type of modified Kahn stereo exciter which allows the user to 'equalize' the sideband response of his system through the antenna, much like having a graphic equalizer on each sideband.  It might be useful for stations with narrow bandwidth directional arrays to flatten out the sideband response, thereby lowering distortion and cranking up the high end response a bit through the system.  This would also enhance the performance of a Kahn stereo station, but since The Flatterer is not compatible with C-QUAM, it is pretty much a dead duck.  However, it could be used with mono-only stations."

"Both of these systems actually do work, in that they generate the signals Kahn claims for them. Whether those signals are useful in the real world is apparently arguable.  I can see POWER-side being an intriguing idea for stations with nasty DA's and deep nulls, since those nulls really only occur at the carrier frequency.  The further you get away from the carrier frequency, the worse the null response gets.  That's why you hear that nasty sounding audio while driving thru a null, instead of just a reduced signal level with no distortion."  

Matt Bailey notes,

"There were stations using a system called POWER-side which was designed to improve alternate channel interference problems by placing most of the modulation energy into one sideband.  Conveniently, it used Kahn ISB AM STEREO transmitting gear as well.  A lot of stations that tried this were old Kahn AM STEREO stations and they usually even left the pilot signal on.  One such station was 1160 WJJD (now WSCR) in Chicago, Illinois.  While listening to WJJD during "The POWER-side years" (with the a tuner that had a multi-synchronous IC), the tuner would switch to "stereo" and play significantly louder in one channel than the other!  And, the louder channel would have more highs and the lower channel would have more bass."

570 WNAX in Yankton, SD, 610 WIP in Philadelphia, PA, 880 KRVN in Lexington, NE, Business Talk Radio 1120 WBNW in Concord, MA, 1430 KEZW Aurora, CO, 1480 WLPH in Birmingham, AL, 1510 KDKO in Denver, CO, 1570 WISP in Doylestown, PA and 1580 WWSJ in St. Johns, MI are examples of some AM stations currently using the Kahn POWER-side.  If you'd like to read about some broadcasters' insights and real world experiences with this product, please click here.  Also, if you know of any other AM stations currently utilizing this technology, please drop me a line at alexk@hfx.eastlink.ca

Please Remember:  The Kahn POWER-side Expander is not a stereo transmission scheme. As Scott Todd points out:

"POWER-side is a monaural use of a stereo technology.  If it were to be used as a stereo system, stations would lose the coverage they've gained by using it.  The high frequency content of one sideband is often deliberately reduced to lessen adjacent channel interference. If you were to restore it to the original stereo content, the interference would return."

My sincere thanks to Tony Straka for providing me with the above photos of the Kahn POWER-side unit which is currently in use at 1570 WISP in Doylestown, PA.  My thanks also to Dave McCrork of WISP who provided Tony with a tour of the station's facilities and graciously allowed him to get some shots of their equipment.


The Harris AM STEREO System

Does anyone remember listening to a Harris-equipped AM STEREO station?  Personally, I have never heard an off-air Harris AM STEREO broadcast, but apparently it had the ability to sound rather good.  This was due to the fact that this system was based on true synchronous detection.  As a result, the receivers that Harris made worked great under skywave propagation situations (i.e., no distortion during selective fading).  The aforementioned receivers made by Harris were never sold to the public, but instead were supplied to stations using their system.  

According to Dave Hershberger, Developer of the Harris AM STEREO system and now Principal Engineer for ADC Broadcast Systems Division in the Grass Valley Design Center in Grass Valley, California:

"I think we had the best system - definitely superior to Motorola, Magnavox and Belar in almost every way.  Under some limited conditions however, the Kahn system was better. But, Kahn had two problems:

1. The system was based on envelope detectors, so it had all of the distortion associated with fading, co-channel interference, directional antenna nulls, etc.

2. The system also had built-in, unavoidable intermodulation distortion in stereo.  This distortion could have been eliminated if he would have modified his system.

The advantage of Kahn was that separation stayed good under adverse conditions (but there was distortion).  The advantage of Harris was that there was never any distortion under adverse conditions (but there could be a loss of separation). 

The ultimate system would have been a compromise between Kahn and Harris, I think: that is, a linear ISB system, based on true synchronous detectors.  It would have had both good separation and no distortion under adverse conditions."          


Suggested Reading

Want to know some more details about AM STEREO?  Check these offerings on the topic:

AM STEREO and The FCC:  Case Study in a Marketplace Shibboleth, Mark J. Braun.

(To see Fritz Messere's review of the the book from the "Journal of Broadcasting and Electronic Media", please click here.)

AM STEREO and TV STEREO:  New Sound Dimensions, Stan Prentiss (1985).

AM STEREO Goes On The Air, Broadcaster, August 2, 1982.  

Build This C-QUAM AM STEREO Converter, Marty Bergen (from the January 1984 issue of Radio-Electronics).

In the October 1984 issue of Electronics Australia, an article was published on how to build your own C-QUAM AM STEREO decoder to add onto an existing AM mono radio.

Motorola Stereo/Audio Circuit Library

AM STEREO, How It Works, John Byrns.  (A Special to The World Wide Web)

An AM STEREO Independent Sideband Mathematical Model, Peter C. McNulty.

Audio Processing for AM Stereophonic Transmissions, Ronald R. Jones (1993).

For an excellent review of the Denon TU-680NAB AM STEREO tuner by Leonard Feldman, please see the Equipment Profile section of the April 1993 issue of Audio (pp.64-68).

For another excellent review of the Denon TU-680NAB AM STEREO tuner by Julian Hirsch, please see the Test Reports section of the May 1993 issue of Stereo Review (pp.42-44).

For a review of the Kraco ETR-1084 Car Radio, please see the May 1991 issue of Consumer Reports.

For a review of the SONY SRF-42 AM STEREO Walkman in Bruce Conti's Broadcast DXing column, please see the February 1998 issue of Popular Communications (p.61) under the heading AMAX AM STEREO.

For those of you who have access to a good Technical Library, John Byrns has graciously passed along to me a short Bibliography on a few of the early AM STEREO systems from the 1959 period to share with everyone:

[1] H.B. Collins, Jr. and D.T. Webb, "Optimized Compatible AM Stereo Broadcast System," IRE Transactions on Broadcasting, PGBC-14, pp. 2-15, November 1959.

[2] H.E. Sweeney and C.W. Baugh, Jr., "New Dimensions in Sound," IRE Transactions on Broadcasting, PGBC-14, pp. 19-23, November 1959.

[3] Charles J. Hirsch, "Progress Report of Panel 1 of the National Stereophonic Radio Committee," Journal of the Audio Engineering Society, Vol. 8, no. 1, pp. 2-6, January 1960.

[4] J. Avins, L.A. Freedman, F.R Holt, J.H. O'Connell, J.O. Preisig and R.N. Rhodes, "A Compatible Stereophonic System for the AM Broadcast Band," RCA Review, Volume XXI, no. 3, pp. 299-359, September 1960.

[5] John M. Hollywood and Marvin Kronenburg, "A Stereophonic Transmission System for AM Broadcasting," Journal of the Audio Engineering Society, Vol. 9, no. 2, pp. 140-144, April 1961.

[6] Norman Parker, Francis Hilbert and Yoshio Sakaie, "A Compatible Quadrature System For AM Stereo," IRE Transactions on Consumer Electronics, Vol. CE-23, no. 4, pp. 454-460, November 1977.  

Notes:

Papers #1 & #2 are part of a special issue of the IRE Transactions on Broadcasting, which was devoted to subject of Stereophonic Broadcasting.

Paper #1 describes the Philco AM Stereo system, and the tests conducted at WABC.

Paper #2 describes the Westinghouse AM STEREO system, and mentions plans for testing the system at KDKA in Pittsburgh.

Paper #3 gives the status of the NSRC, National Stereophonic Radio Committee evaluations of the AM and FM stereo systems that were under consideration at the time. It includes brief descriptions of all the systems, and their similarities and differences.

Paper #4 is a 61 page article describing the RCA AM Stereo system, and includes an extensive analysis of the RCA system, laboratory test results, and the results of field tests conducted with WNBC.

Paper #5 describes the CBS AM Stereo system, and the experimental installation at WCBS.

Paper #6 is an early paper that describes the Motorola C-QUAM AM Stereo system.


AM STEREO RULES!!

You know, I honestly thought I was the only one on the planet who felt this way.  Apparently, and wonderfully, I was mistaken.  Never in a million years did I ever expect to receive the reaction that I've been getting as a result of putting this page together.  I am both truly speechless and extremely appreciative to say the least.  As a result of all the information, stories, and kind words of encouragement I have been receiving since I put this page up last week, it started me thinking and I'd like to share these thoughts with all of you.  But first, I want to share the following e-mail I received entitled "My Experiences in AM STEREO" with everyone. The author wished to remain anonymous, but I must say that this story both moved and enraged me equally:

"Boy, you brought back some memories of the "bad old days" of AM Stereo!  Back in the 1980's,  I was "The Chief" of WNFL 1440AM Radio in Green Bay, Wisconsin.  Station Management decided to get on the bandwagon and go AM Stereo around 1983-84.   Our first step was to rebuild our transmitter plant (which we did...a new Harris MW-5A, a 5-Kilowatt box).  I then did a major studio renovation.   We scrapped the old 1970-vintage mono studio and installed a modern studio console...re-did the furniture...the whole bit."

"Our Corporate Office decided for me that we were to go with the "Harris" stereo system because that is what the other two stations in our Group had installed.   At that time, C-QUAM was just coming around as becoming the market-decided "standard".   It was still a free-for-all as to what system would "win".  Remember, at that time Ronald Reagan was into this "free marketplace" bullshit on how he was running the economy.  He seemed to be quite successful in lowering interest rates and stimulating our poor economy at the time, but.his "boys" at the FCC were using this method to determine what Stereo Standard would be chosen for AM Radio... what folly!!!"

"As things turned out, due to the FCC deregulating radio, my station was soon put on the block for sale (like 90% of all Stations were in the 1980's).  The owners shut off the money supply to our station for upgrades and capital improvements.   The stereo generator was never ordered, even though our Station Van and even company letterhead stationery claimed us to be "WNFL AM STEREO 1440".   To this day, some three owners later, WNFL is still not stereo.   The beautiful on-air studio and upgraded transmitter plant is still pumping out Mono.  Did you know that WDUZ and WGEE (the other two AM's in the Green Bay market) went stereo at the time WNFL was supposed to?  They got wind that I was getting ready to order the equipment for 'NFL and so (this was a VERY competitive market on AM in 1984) they wanted to "beat" us... they both went stereo at about the same time.   Well, you know the rest of the story.   I think to this day they are both still broadcasting in C-QUAM.  You may want to look them up."

"Too bad the government dropped the ball on assuming its role to develop (quickly) a standard for AM STEREO.   I always tell people that we'd still be watching black-and-white TV if the FCC of 1952 was run like the FCC of 1982.  On the Broadcaster side of the coin, do you remember all the in-fighting with Leonard Kahn, Motorola, and Harris?  What a circus!  And all that time, AM radio was dying a slow death. There seems to be enough blame to go around!  As for me, I got "the hell outta" radio.  I left Broadcasting after 15 years in 1989.  It's too bad that AM radio is dead.  I miss it.  The 'AM STEREO Years' were an exciting time for those Engineers that were there!"


Hmm...

AM radio dead?  AM STEREO dead?  I hardly think so!  After the reaction I've been getting lately, there is nothing farther from the truth.  (I'm especially glad to hear all those stories from individuals who have actually taken their old AM STEREO equipment "out of storage" and actually hooked it back up to their main stereo equipment!!)  With this in mind, all I ask is that if you are somewhere listening to an AM STEREO station and you are enjoying it, kindly let me know about it, but more importantly, let the powers that be at that particular station know about it too.  Tell them they should promote the fact that they are an AM STEREO operation.  I'm sure they would appreciate hearing this; after all, if it wasn't for the listeners, they wouldn't be in business in the first place.  As for myself, I have always felt that it is nothing short of a crime that people who have the desire to listen to an AM station in stereo can't because of the absolutely pathetic lack of AM STEREO capable receivers available.  Write to these manufacturers and complain!! (especially SONY, AIWA, and DENON.)  You see, the way I figure it is that little 'ol me paying a station a compliment or writing a letter to SONY probably won't do much; however, if we fans of AM STEREO as an aggregate do these things, who knows what could happen?  As a lifelong fan of radio in general, nothing would make me more happy than to see every radio sold have AM STEREO capability. After you experience AM STEREO, AM mono can't even compare.  It is, after all, "the sweetest sound this side of Heaven."


And Last, But Not Least...

Your feedback, comments, questions, concerns, corrections, and additions are both important to me and always welcome.  Please drop me a line at alexk@hfx.eastlink.ca and let me know how you ended up here and what you think.  If you know of any AM STEREO stations broadcasting in your area, please let me know about them (please include frequency, calls, and format).  Also, if you have any links to any webpages of AM STEREO stations, let me know and I would be happy to list them here.  

Just so you know, it is my "policy" to give full credit to all contributors to this page if you so desire.  Additionally, if you send me something and wish to remain anonymous, then I will fully respect your wishes.  The way I see it is, if you have shown me the courtesy to take the time and write to me with info (which I appreciate immensely), then the least I can do is acknowledge it on my page, while at the same time respecting your privacy where applicable.  This is something which is important to me personally at all times.  If you don't explicitly say that it's OK to use your name on my page, then I will not give you a credit without clearing it with you first. If you have recently sent me something and/or your name or link does not appear, that's why.  All you have to do is let me know and I would be more than happy to fix things up.   

Until next time, thanks so much for dropping by, and please come again!  

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