Broadcasting systems AM stereo

1 broadcasting systems

1.1 harris system
1.2 magnavox system
1.3 motorola c-quam
1.4 kahn-hazeltine
1.5 belar system

broadcasting systems

the magnavox pmx, harris corporation v-cpm, , motorola c-quam (compatible—quadrature amplitude modulation) based around modulating phase , amplitude of carrier, placing stereo information in phase modulated portion, while standard mono (l+r) information in amplitude modulation. systems did in similar (but not compatible) ways. original harris corporation system later changed match motorola c-quam pilot tone indicating station in stereo, making compatible c-quam receivers.

harris system

this system, known v-cpm variable angle compatible phase multiplex, developed harris corporation, major manufacturer of radio/tv transmitters. incorporated left minus right component frequency modulated 1 khz. harris successor pioneer gates radio line, has changed name in 2014 gates-air. harris system changed pilot tone compatible c-quam, after c-quam became more popular , eventually, fcc approved standard. cklw in windsor, ontario, canada (also serving nearby detroit, michigan) among first stations broadcast in harris stereo. harris system no longer used in original form.

magnavox system

this system developed electronics manufacturer, magnavox. phase modulation system. declared stereo standard fcc in 1980, fcc later declared stations free choose system. harris system, popular in 1980s, stations stopped broadcasting in stereo, or downgraded c-quam system time went on. 1190 wowo in fort wayne, indiana (then) 50,000-watt clear channel magnavox flagship station.

motorola c-quam

c-quam developed , promoted motorola, longtime manufacturer of two-way radio equipment. became dominant system late 1980s, , declared official standard fcc in 1993. while many stations in usa have since discontinued broadcasting in stereo, many still have necessary equipment so. c-quam still popular in other parts of world, such canada, japan, , australia declared official standard.

quam uses quadrature phase , amplitude modulation: phase of audio rotated ahead or behind carrier , amplitude of each phase changed; giving 16 points reference (used in dialup modems past 9,600 bit/s limit on analog lines). quam signal (left minus right, or l-r , information) phase modulated on transmitter (the quam exciter replaced crystal in transmitter) , left plus right (or l+r ) still modulated transmitter had in past. c-quam modified quam , called compatible (the c- in c-quam ).

c-quam had been long criticized kahn-hazeltine system s creator, leonard kahn being inferior system. first generation c-quam receivers suffered platform motion effects when listening stations received via skywave. later improvements motorola minimized platform motion effect , increased audio quality , stereo separation, on amax-certified receivers in 1990s.

kahn-hazeltine

the kahn-hazeltine system called isb developed american engineer leonard r. kahn , hazeltine corporation. system used entirely different principle—using independently modulated upper , lower sidebands. while station using system sound best proper decoding, possible use 2 standard radios (one tuned above , other below primary carrier) achieve stereophonic effect, although poor stereo separation , fidelity compared proper kahn system stereo receiver. 1 of best known stations use kahn system 890/wls, chicago. wls still transmits in stereo today uses motorola c-quam system instead.

however, kahn system suffered lower stereo separation above 5 khz (reaching none @ 7 khz whereas fm stereo has 40 db or more separation @ 15 khz) , radio antenna array on directional (common on lot of nighttime , daytime stations) had have flat response across entire 20 khz channel. if array had higher reactance value (leading higher standing wave ratio) on 1 side of frequency vs other, affect audio response of channel , stereo signal affected. also, kahn refused license radio receivers manufacturers design, although multi-system receivers manufactured various companies such sony, sansui, , sanyo, receive of 4 stereo systems.

nonetheless, system remained competitive c-quam late 1980s , kahn vocal advantages on motorola s system. kahn filed lawsuit claiming motorola system did not meet fcc emission bandwidth specifications, time, c-quam had been declared single standard stereo in usa.

kahn s stereo design later revamped monaural use , used in power-side system, in decreased signal in 1 sideband used improve coverage , loudness, directional antenna arrays. power-side became basis cam-d, compatible digital, new digital system being promoted leonard kahn , used on several stations.

kahn receiver chips have been used inexpensive method providing high frequency (world band) receivers synchronous detection technology.

belar system

the belar system used in limited number of stations, such wjr. belar system, designed rca in 1950s, simple fm/am modulation system, attenuated l-r signal frequency modulating carrier (with 400 µs pre-emphasis) in extent of +/- 320 hz around center frequency, , l+r doing normal high level modulation (usually referred plate modulation in transmitters using tube in final stage, audio applied plate voltage of tube; in solid state transmitters, various different techniques available more efficient @ lower power levels). belar system (by company of same name) dropped due issues design though easier implement other systems. , kahn system did not suffer platform motion (which killer stereo @ night; platform motion stereo balance shift 1 side other , center) use of low level frequency modulation did not permit high separation of l , r channels.