I drew up a AM Stereo time-line [LINK] years ago but never really dug into the subject. It's time to revisit the war between Motorola and Kahn. First I should admit that there were more than two players. In D.C. we have two major parties, but there are a number of smaller groups that bear mentioning. It was the same with AM stereo. The top five were as follows:
- Motorola (C-QuAM)
- Kahn-Hazeltine (Independent Sideband AM aka "ISB")
- Magnavox (PMX)
- Harris Broadcast (V-CPM)
- Belar System
Motorola's C-QUAM was invented in 1977 and was used widely in both the US and Canada and showed early signs of becoming a standard. But fast forward to 2014 and you can count on your fingers the number of American stations still using it: WLS-AM, WNMB-AM, WBLQ-AM, WIRY-AM, WAXB-AM and WLAD-AM. It's patents have expired and it is generally accepted as the international standard for AM Radio broadcasting despite being incompatible with IBOC. Despite those poor North American numbers... if there was a winner it was Motorola. The FCC finally adopted it in 1994.
Leonard R. Kahn's system didn't go quote as far. But he was a true believer. He was an AM radio evangelist. He once actually said "There is no limitation to the fidelity of AM radio. From a mathematical standpoint, AM does better in frequency response than FM." This is complete malarkey of course. Because an AM radio station has a maximum bandwidth of 20 kHz, it is patently and inherently inferior to an FM station with 200 kHz of bandwith. On that comment he was wrong by a full exponential order. More here and here. But Kahn had more than 100 patents and his AM stereo patent was granted in 1958.He tested the technology on WQXR-AM in new York in 1956.
He criticized the system for it's "platform motion" effects. While later revisions diminished the problem,it's stereo audio was susceptible to skywave interference.The result was a moving stereo balance with the audio "center" moving left and right randomly. It was true and even in the FCC order that declared it the standard they admitted that the problem was never completely resolved. But he also made a legal attempt to block Motorola from using its C-QUAM in the US entirely. In 1986 he filed a complaint claimed that C-QUAM violated FCC emission bandwidth specifications: specifically 73.44. He was right, but he was nit-picking. In the end C-QUAM won because they had the most radios on the market, and the majority of stereo AM broadcasters were using their system. The FCC adoption specifically mentioned other countries using the system. C-QUAM did not win because if technical superiority. It was a lesson that Ibiquity took to heart a decade later.
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Kahn wasn't the only believer in the high-fidelity of AM, but he came later than a proposal the crashed and burned in 1950. These articles are from Broadcasting Magazine. (Parenthetically, Tarzian's "regional station" mentioned in the first article was the third AM to go on the air in Bloomington, and the only station to survive more than a few years. It's still operating, and still owned by the family.)
ReplyDelete1948-05-03-BC-OCR-Page-0026
HIFAM
Radio Service for Non-Radio Towns
By LARRY CHRISTOPHER
FREQUENCY-SAVING, economical and "very satisfactory" broadcast service for small non-radio communities was envisioned as a practical reality last week by Sarkes Tarzian, consulting engineer and operator of experimental station W9XHZ Bloomington, Ind.
The system, a method of high-frequency AM broadcasting, is called HIFAM.
The HIFAM proponent stated the system is not new, others having experimented with it for many years and even before introduction of FM, but that it now has been placed on a practical, economical basis. It is an adaptation of what formerly was known as "apex" or high-fidelity high- frequency broadcast transmission, which gave way a decade ago to FM in the same frequencies.
Mr. Tarzian appeared all day Wednesday before FCC Hearing Examiner J. Fred Johnson to report
on the experimental work of W9XHZ, which has been operating on 87.75 mc with 200 w and AM emission since May 1946. He told the Commission:
• HIFAM requires only a 10-kc channel (to FM's 200 kc) to deliver a relatively static and interference-free signal to a community area.
• A $5.95 converter makes any AM receiver adaptable to HIFAM.
• Combination standard band-HIFAM sets can be made to retail for $29.95.
• HIFAM can be received on FM sets, too.
• HIFAM receivers are stable; "tired" components do not cause distortion as in aging FM sets.
• The economic factor aids the broadcaster, with a HIFAM station costing about $12,000.
cont.
`Not a Competitor'
ReplyDeleteMr. Tarzian told BROADCASTING he did not consider HIFAM a competitor to any method of large- city, high -power broadcasting -AM or FM -but rather as a workable, low price service for those small towns which do not have a local station or - adequate nighttime service. He estimated he could provide a good radio service with HIFAM to several thousand small communities in the U. S., Canada and Mexico with a 400 -kc band divided into channels of 10 kc each.
Some quarters last week had expressed considerable concern that HIFAM would only "muddy the waters" of the FM controversy to an even greater extent, or that it was just more snipe- shooting at an industry problem already settled.
At the hearing on W9XHZ progress, Commission Counsel David S. Stevens indicated the proceeding had of been called to consider the comparative merits of FM and HIFAM but to inquire solely into the issues of the case. These were whether the operation of W9XHZ "has shown the existence of any technical advantage of AM broad-casting at very high frequencies" and whether the continuance of the station "would serve to advance the broadcast service."
It as pointed out that the Commission in allocations Docket 5805 in 1940 had weighed fully all the merits of high-frequency AM and FM and overwhelmingly chose FM [BROADCASTING, June 1, 1940].
In defense of his experimentation, Mr. Tarzian told of favorable public acceptance of HIFAM in the Bloomington area. He said he now wished to place another station on the same frequency about 100 miles from Bloomington, at Marion, Ind., to study co- channel interference and other characteristics. Further plans call for an additional transmitter in Bloomington for adjacent channel experimentation.
Mr. Tarzian also produced for the record a number of letters from listeners to his station as well as comments from leading manufacturers. All expressed favor or interest
in the work.
Thomas T. Goldsmith Jr., director of research for Allen E. DuMont Labs., stated the "sound quality available in the range of carrier frequencies from 40 to 100 mc using AM is excellent and the further testing of this method is certainly in the public interest."
Mr. Goldsmith pointed out that DuMont is "very much interested in tests, since we also have done broadcasting in this range of frequencies, using AM on the television sound channel."
Requesting reports of further tests, Mr. Goldsmith continued: "In view of interest in studies of methods of sound transmission for television on the higher channels, I would like to suggest that you also investigate the possibilities of AM sound transmission on carriers between 500 and 900 mc."
William J. Schnell, director of engineering for Sentinel Radio Corp., stated he believed the HIFAM operation was workable. He cited: reception on the high frequencies. "is usually free of atmospheric and man-made electrical disturbances "; high band operation "provides for the utilization of a band width which permits a high fidelity modulation spectrum giving high musical quality to the listener "; converters are cheap and usable on AM sets, and that "the propagation characteristics of such frequencies are such that practically no interference at any time occurs outside the effective service area on the operating channel."
1949-06-27-BC-0063
ReplyDeleteHIFAM RENEWAL
Tarzian Station Is Favored
INITIAL decision was reported by FCC last week to grant renewal of license to Sarkes Tarzian's experimental HIFAM station at Bloomington, Ind. The initial decision was by Hearing Examiner J. Fred Johnson Jr. HIFAM is the term coined by Mr. Tarzian to describe the high-fidelity, high frequency amplitude modula- tion system of broadcasting employed by his station, KS2XAP, formerly W9XHZ [BROADCASTING, May 3, 1948], The station has been operating since spring of 1946, airing various types of programs for the Bloomington area. The station
operates on 87.75 mc with power about 200 w and using AM emission.
Mr. Tarzian and his wife are owners and operators of standard station WTTS Bloomington, which recently commenced operation on 1370 kc with 1 kw daytime and 500 w nighttime. They also are permittee for a new television station
there. Mr. Tarzian, a radio design engineer, built WTTS and the HIFAM station himself. He formerly was chief engineer of the RCA Bloomington plant and during the war was chief engineer and production manager of the whole RCA VT fuse program.
Mr. Tarzian told the Commission that HIFAM requires only a 10 kc channel (to FM's 200 kc) to deliver a signal of comparable quality to FM reception. The initial decision pointed out that Mr. Tarzian's experiments also show that HIFAM involves no problem of multipath distortion as does FM.
Further advantages of HIFAM were reported to be that it can be received on any AM set with use of a $5.95 converter; it can be received on FM sets without any adjustment, and combination AMHIFAM receivers could be marketed for $30.
Mr. Tarzian indicated that HIFAM was ideal for instituting hometown radio service in small non-radio communities because of its frequency saving and economic characteristics. A HIFAM station would cost only about $12,000.
The examiner's decision pointed out that Mr. Tarzian plans to expand his HIFAM experimentation by establishing another station in Bloomington and another in a town about 100 miles away to study interference factors. Study and research in equipment also would be continued. Simultaneous airing of WTTS shows on the HIFAM outlet also would aid in comparison studies, it was pointed out.
And now, the conclusion:
ReplyDelete1950-06-05-BC-0046
HIFAM RENEWAL
Denied By FCC
EXPERIMENTAL high frequency AM station ("HIFAM") KS2XAP Bloomington, Ind., operated by Sarkes Tarzian, was denied renewal of license by FCC last week. Given a conditional renewal in mid-April, the outlet was operating on 87.75 mc [TELECASTING, April 24]. FCC then ruled the license would expire June 1 and that the station could not operate when WFBM-TV Indianapolis was telecasting on Channel 6 (82-88 mc).
Mr. Tarzian also operates WTTS and WTTV (TV) Bloomington.
Very interesting that W9XHZ operated in the FM band. Very telling too. I shoudl read up on that one.. very arcane!
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