FM Broadcasting History - Various Articles

Yankee Frequency Modulation About Ready

Armstrong Method To Go on Air in June

The first step in providing a radically new and potentially revolutionary broadcast service to New England, using the frequency modulation system invented and developed by Maj. Edwin H. Armstrong, Columbia University professor and pioneer inventor of the superheterodyne circuit, will begin early in June from the Yankee Network's new high-frequency broadcast station W1XOJ.

The station, under construction since last November, is located on the summit of Asnebumskit Hill in the Town of Paxton, Mass., near Worcester. The Armstrong system [Broadcasting, Feb. 1, Apr. 1] is called frequency modulation to distinguish it from the conventional system under which most broadcast stations now operate, known as amplitude modulation. It not only requires a new type of transmitter, which is manufactured by Radio Engineering Laboratories, Long Island City, N. Y., but also a new type of receiver, now in production at the General Electric and Stromberg-Carlson plants.

It is expected that the single transmitter at Paxton will serve all of Southern New England with "staticless" reception equivalent to that available form any local station. Program material will be supplied by the Yankee, Colonial, NBC and MBS networks, being broadcast simultaneously with that of the Shepard-served stations. John Shepard 3d, president of the Yankee and Colonial networks, has evinced such great faith in the system that the network is expending some $200,000 on the experiments. Having pioneered in directional antennas, halfwave vertical radiators, live and dead end studios etc., he and his technical staff predict that W1XOJ will demonstrate such a superiority over the present method of broadcasting that eventual results will revolutionize the art.

The transmitter site of W1XOJ is about 1,400 feet above sea level. Remote from roads, power and water, it was necessary to build over a mile of road and power line through woods and pasture land and drive a well 575 feet through solid rock. The first units of the transmitter are being tested and will soon go on the air on a regular test schedule with power of about 2,000 watts. By autumn it is expected that construction for the authorized power of 50,000 watts will have been completed and put in regular service. The frequency is 43,000 kc.

To assure maximum coverage, the radiating system consist of a four-bay turnstile array located at the top of a 400-foot guyed mast. To minimize the effects of ice on the radiating system, concentric transmission lines are used in place of the conventional open wire feeder system. Tests of the radiating system prove definitely that the array concentrates the radiation in the vertical plane and directs radiation to the horizon by an amount equivalent to four times the power with a simple antenna. Shunt exciting the 16 individual elements of the array through capacitors reduces standing waves in the transmission line to a few per cent.

Of perhaps as great interest as the inauguration station is another pioneering project connected with it. Asnebumskit Hill in Paxton is 42 miles air line from the Yankee Network studios in Boston. Convinced from the demonstrated results of Maj. Armstrong's system that it renders a higher quality service than is available from the regular wire services, the programs are transmitted from the Yankee Network studios to W1XOJ by a frequency modulated relay broadcast station. This station, W1XOK, is located in a penthouse atop the studio building and transmits on 133,030 kc. with 250 watts.

The relay station employs a directive antenna system at the top of an 80-foot mast located on the studio building. This array gives an equivalent measured power gain of about tenfold. The signals from the relay station are received at Paxton with an array of V antennas which give a further equivalent power gain of over fiftyfold. Tests during the winter and to date indicate that this radio link between the studios and broadcast station will transmit without appreciable distortion a frequency range beyond the limit of human hearing without appreciable noise.

"When W1XOJ goes on the air on regular schedule, listeners will be given the opportunity of hearing programs with the full tonal range and freedom from noise that is obtained in the studio monitors," according to Paul A. deMars, Shepard's technical director. "When the transmitter is operated with the full power of 50,000 watts, it is expected that a broadcast service free from interference and of a quality limited only by the art's development of sound reproducing devices will be available to all listeners within about a 75-mile radius. Included in this radius are the metropolitan areas of Boston, Springfield, Providence, Hartford, Worcester, Fall River and New Bedford, which together with the other cities and towns in this area have a population in excess of five million people.

The beginning of this new broadcasting service is the outcome of the meeting of Mr. deMars and Maj. Armstrong in the spring of 1936. Convinced that Armstrong had disclosed an invention applicable to broadcasting in the ultra-high frequencies which would revolutionize the art, Mr. deMars proposed to Mr. Shepard that Yankee Network experiment with the system. Experience with conventional methods of broadcasting in the ultra-high frequency band had convinced Mr. deMars that no improvement could be expected over the regular broadcasting system.

Addressing the FCC at the general hearing of June 15, 1936 on the allocation of ultra-high frequencies, Mr. deMars along with Maj. Armstrong emphasized the possibilities of frequency modulation applied to broadcasting in the high frequencies and urged the Commission not to promulgate an allocation scheme that did not provide ample opportunity to demonstrate the system.

Shepard heard demonstrations of Armstrong's system in the fall of 1936 both in New York and Bayport and Westhampton on Long Island. He was so impressed by the reception from the 500-watt transmitter of C. R. Runyon, in Yonkers, operating on 110,000 kc., that he authorized the project which is now nearing completion on Asnebumskit Hill.

Under date of Sunday, May 14, Henry M. Lane, engineer and technical radio editor of the Boston Post stated in an article about W1XOJ, referring to the relay transmitter W1XOK:

"We have listened to this signal in and near Boston and in Paxton. The tone fidelity of the reception is the finest we have heard on any radio reception. What is more striking at the moment, the reception is absolutely quiet with no sign of static, tube noise or transmitter carrier noise. This applies whether listening nearby or at considerable distance from the transmitter.

"It is expected, then, that this new system of broadcasting will provide the listener with greatly improved fidelity. The tests on the 250-watt transmitter at Boston, which include measurement from the microphone terminals to the loudspeaker terminals of the receiver, are said to be flat within two decibels from 30 to 17,000 cycles per second with no measurable harmonic distortion. The loss is but 7 db. at 30,000 cycles per second. This is approaching nature herself when it comes to reproducing audible sounds.

"The system includes a unique method of signal amplitude control which, to use more familiar language, is an improved automatic volume control. There is no fading of the frequency modulated signal. It is not disturbed by noise fields from electrical machines. No amplitude changes affect the receiver output. It responds only to changes in frequency.

"Listening to the reception one is particularly impressed by the quiet background. The system will reproduce silence. This lends materially to the naturalness of reproduced sound. Everything from full orchestra volume to a pin-drop can be heard.

"The quality of performance achieved with relay station W1XOK and broadcast station W1XOJ," Mr. deMars stated in Broadcasting, "does not result simply from the use of a system of frequency modulation. The transmitting equipment of these stations was designed by Maj. Armstrong and Mr. Runyon, who from years of experimentation and development have reduced to engineering practice the wide band system of frequency modulation invented by Armstrong.

"Their achievement has created a new standard of performance for the broadcast art. The transmitters and speech input equipment of both stations were manufactured by the Radio Engineering Laboratories, New York. The equipment sets new standards of quality of materials, workmanship, accessibility and efficiency from microphone to antenna. Both transmitters use Eimac tubes in the final stages. These tubes perform with an efficiency power output and length of life not exceeded by power tubes at the medium frequencies."

Stations Using Armstrong Modulation Now in Operation or Under Construction

Location              Owner                   Power

*Alpine, N. J.        Maj. E. H. Armstrong    20-40 kw.
Washington, D. C.     Jansky & Bailey         1 kw.
Mt. Washington, N. H. Yankee Network          2 kw.
New York, N. Y.       J. V. L. Hogan          1 kw.
Storrs, Conn.         D. A. Noble             100 w.
**Rochester, N. Y.    Stromberg-Carlson       2 kw.
Meriden, Conn.        F. M. Doolittle         1 kw.
Schenectady, N. Y.    General Electric        10 kw.
Pittsburgh, Pa.       Westinghouse            10 kw.
Springfield, Mass.    Westinghouse            1 kw.
*Paxton, Mass.        Yankee Network          50 kw.
*Yonkers, N. Y.       C. R. Runyon            500 w.

*In experimental operation.

**CP applied for.

PICTURE CAPION: Turnstile array and transmitter of W1XOJ and W1XOK, the units of the Armstrong frequency modulation system which John Shepard 3d is placing in operation at Paxton, Mass., this month. Left photo shows the radiator of W1XOJ, 2,000 watts on 43 mc., to be raised to 50,000 watts this fall, in course of construction before being erected atop a 400-foot mast at Paxton. Center photo shows the modulated relay broadcast transmitter of W1XOK, 250 watts on 133.03 mc., installed in a penthouse atop the Yankee Network studio building in Boston to transmit from an 80-foot mast to Paxton, 42 miles away, for relay via W1XOJ. Right photo shows the concentric transmission line feeders at the base of the turnstile, with Dr. Greenleaf Whittier Pickard, noted radio scientist (left) and Paul A. DeMars, Shepard's technical director.

WOR Seeks FM Site

WOR engineers are surveying the New York metropolitan area in search of the best site for the new 1,000-watt frequency modulation station recently authorized by the FCC. Station will operate on 43.3 mc. with the call letters W2XWI. J. R. Poppele, chief engineer of WOR, has inspected the experimental work with this new type of broadcasting at the General Electric laboratories in Schenectady and at W2XMN, Alpine, N. J., station erected by Major E. H. Armstrong, inventor of the system.

New York F-M Station Is Proposed by Yankee; Says New Art Is Ready

Holding that frequency modulation has passed the experimental stage and is ready for everyday operation, Yankee Network, pioneer experimenter with the new "staticless" system of transmission and reception invented by Prof. Edward [sic] H. Armstrong, has applied to the FCC for authority to erect two more F-M transmitters -- one in the New York metropolitan area and the other on Mt. Washington, N. H.

Yankee is now operating W1XOJ atop Mt. Asnebumskit, near Worcester, using 2,000 watts on 43 mc., and early next year will raise its power to 50,000 watts. A relay station, WEOD, carries F-M signals from Boston to the transmitter, 43 miles away, using 250 watts on 133.03 mc. Great success has been achieved with the system, leading to the conviction that it is ready to go beyond the experimental stage.

The proposed New York station would operate with 50,000 watts on 43 mc., using a seven-bay turnstile on Prof. Armstrong's tower already erected for his W2XMN at Alpine, N. J. The Mt. Washington station would operate with 5,000 watts on 42.6 mc., and would utilize the experimental plant already installed there by Yankee under the direction of Paul A. deMars, Yankee chief engineer.