Without doubt, AM transmissions can sound as good as FM, but the transmitters do need extra band space to make the audio sound right. To combat interference effects, manufacturers have reduced the IF bandwidth of AM receivers, reducing AM's ability to sound clear and bright.
We have been champions of AM STEREO transmissions since first hearing it in the early 1980s. Subsequent work on two systems (Kahn-Hazeltine and Motoroal C-QUAM) with broadcasters convinced us that this is the way for AM to move, but historically the quest to cram in more and more small low power transmitters has worked against AM, leaving the band full of low quality equipment.
Every Breath You Take POLICE
on HBC, 1287 AM Stereo, Sapporo Japan
Classic 1983 #1 smash hit, as received in analog C-Quam AM Stereo in Japan via night time skywave in the Tokyo area, 500 miles away from Sapporo.
Yes, a 500 mile night time path
- and it still sounds great!
The audio quality is among the best we've ever heard from analog AM radio, thanks to an excellent receiver, very quiet band conditions, and the Orban Optimod-AM 9100 audio processor. 12.5 kHz audio bandwidth with stereo enhancement added
AM Stereo Exciter
The excellent Harris AMS-G1 C-Quam AM Stereo exciter is seen here being put through its paces. This is a technical review and includes a long look 'under the hood' of the equipment.
This is not the older VPCM AM Stereo system that Harris developed themselves, but the better known C-Quam system, which is still in use on around 300 stations in France, Australia and the USA.
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. Many of the above products were only sold in Canada and Australia and were never introduced to the American marketplace.
(Courtesy of AMStereo.com
Transmission & Stations
AM Stereo provides clear full-dimensional Stereo sound that envelops the listener with fidelity usually thought of as something only found on the FM band. AM Stereo has been used all around the world for over two decades and is employed by hundreds of stations on every continent. Since its introduction, millions of AM Stereo receivers have been sold for home, car, and portable listening enjoyment.
AM Stereo is an analogue system that has been optimized for high quality (meaning good audio fidelity) reception even with weak, distant signals. The greater long-distance range of AM signals, especially at night, gives stations a much larger coverage area, extending hundred and often to thousands of miles. FM by contrast is limited to little more than 'line of sight', a maximum of perhaps 70 miles if the highest locations are chosen for transmission.
The big advantage of AM Stereo is that it not only reaches huge distances, but it is reverse compatible with existing mono receivers. They receive the same programme and with quite an improvement in audio quality too.
AM Stereo is a lot cheaper to install than other systems, such as DRM or IBOC. Its cheaper for the transmitter and listeners do not need to upgrade to continue receiving the station.
Here's what the AM STEREO web site says:
"The benefits of AM Stereo are well suited to every programming format, as its greater realism and superior frequency response adds just as much enjoyment and excitement to news and talk programs as it does to music.
AM Stereo programming
Sporting events and live performances especially come alive in Stereo with stunningly realistic detail, while voice and music is received with greater clarity and richness of sound, even if monaural audio sources are used. Commercials, jingles, and station IDs are particularly effective at immediately catching listeners' attention when they are broadcast with dramatic Stereo effects.
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All Rights Reserved. Reproduction strictly prohibited.
Power 1490 Tucson Arizona
Dance Music in AM Stereo
for the 1990s generation!
From 1991 to 1995, "Power 1490" KJYK in Tucson was the hippest dance station in Arizona, and they broadcast in AM Stereo. The quality of this 'Sound of the Dessert' station was supendous - it simply sizzled. By the 1990s, American kids had enjoyed FM radio for a couple of dedades but they were happy tuning to this AM station.
Listen now to understand what the quality was like - these are 'off the air' telescoped air checks of the Power 1490 transmissions, at about 30 miles away!
THE GORT is
WXYG in Minnestota
Classic Album Hits format.
On 540 AM and worldwide
Stereo sound was first developed in the early 1900s and made its first commercial appearance on some film soundtracks in the 1930s.
In the 1950s, some AM engineers designed a system that could give good stero reception, notably Leonard Kahn, a brilliant radio engineer who lived in Connecticut. The Kahn system was put on the market around 1980 and was one of five rivals being developed. They each had good and bad points.
An example of the problems was 'Platform Motion', which the C-QUAM system suffered from. After dark the skywave would come in out of phaser with the groundwave. As the two varied in phase this could cause the audio to swing from the left to the right speakers, and back again, which could be very disconcerting, especiallly while driving!
In the 1960s, engineers turned their attention to adding stereo to FM transmitters, which were very much a backwater in commercial radio terms. With the addition of stereo and the lack of amplitude interference, the FM band quickly became dominant for music programmes.
Each of the AM Stereo systems had their foibles and faults but just as it was decided that the FCC would give their blessing to the Harris system, the lawyers decided that it would be fairer if the market place were allowed to decide which system became dominant.
Brief History of AM STEREO stations & listening
Why do stations transmit AM Stereo?
To broadcast in AM stereo needs stereo programme sources, an exciter adding to your transmitter and the chain adapting to AM stereo, usually by some modifications to the bandwidth.
The exciter is usually the only new item a radio station needs and the cost is around £5,000. Motorola, NEC and Delta Electronics manufacture the necessary AM Stereo Exciters, details of the Delta ASE 2 can be found HERE.
Sadly, the US regulator, the FCC, left the market to decide which system won, and the money guys able to roll their system out won with the C-QUAM system, whose main developer was Motorola. It finally became dominant by the early 1990s with Kahn, Harris and Magnavox pulling out..
The FCC finally made its decision in 1993, but by then the AM band had become ravaged and damaged by the AM Stereo wars.
Mototola have since made many changes to their system and have largely conquered its problems, such as Platform Motion.