The Radio Corporation of America was formed in 1919 as a General Electric subsidiary, taking over the former operations of American Marconi. RCA's primary objective was to be the premier international radio communications company in the United States. As it expanded its operations, in 1921 it opened the first part of its showcase "Radio Central" facility, which was located at Rocky Point, Long Island, New York. At the time Radio Central was being developed, G.E.-produced Alexanderson alternator-transmitters were considered the clear best choice for long-distance radio service. Thus, as outlined in this chapter, the plan was for the facility to eventually operate ten of these massive machines. However, only two alternators were ever actually installed.
The Alexanderson alternators transmitted on longwave frequencies, and longwave transmitters require especially lengthy antennas, so, the site drawings show an impressive circle of twelve huge antennas, each about 1.5 miles (2+ kilometers) long, and arranged in a spoke pattern surrounding the alternator buildings. But, although two antenna spokes were constructed in 1921, the other ten never were. The reason the alternator-based portion of Radio Central never got beyond a truncated two alternators plus two antenna spokes was due to an unexpected revolution in radio transmission -- just a few years after construction began, it was learned that shortwave transmitters could span international distances at a fraction of the power and cost of the longwave alternator-transmitters. (In a 1968 interview, RCA engineer Harold Beverage remembered a 1926 Rocky Point test which showed that a small shortwave transmitter, using just a 25-foot (8 meter) long antenna, could be more readily heard in South America than the 200-kilowatt alternator longwave transmissions. Incidentally, the text below refers to amateur station 2BML, which was Beverage's personal callsign.)
So, ironically, it turned out that the magnificent Alexanderson alternators, so glowingly reviewed in this article, were acually just a couple of years away from becoming "inefficient, outdated dinosaurs" that would be rapidly overshadowed by far more efficient vacuum-tube shortwave transmitters.
The Book of Radio, Charles William Taussig, 1922.
THE WORLD'S GREATEST RADIO STATION
All the wonders of radio that have transpired within the last twenty-five years seem to have been collected and concentrated at Rocky Point, Long Island (seventy miles from New York), which we shall now visit.
Radio Central.--A photograph of the Antenna of Radio Central gives one the impression that it has an appearance of a transmission line. This, however, is not the case on actual approach. The impressiveness of those twelve giant towers cannot adequately be portrayed in a photograph, nor indeed can mere words do them justice. The two completed antennæ, consisting of six 450 foot high towers, bearing sixteen wires on 150 foot cross bars, stretch for three miles in an almost straight line. "Sentinels of World Wide Wireless," the Radio Corporation calls them, and they certainly look the part.
Approaching the power house from the main road by automobile over the private road of the Radio Corporation, aptly called "Jonah Road," one loses some of the enthusiasm that the first sight of the towers inspired. Wallowing in mud up to the hubs of an automobile, and getting stuck every now and then, leaves one in somewhat of a diffident attitude regarding the wonders of modern science. Once inside of the power house, however, and cordially received by Chief Engineer G. L. Usselman and his assistant, Mr. F. A. Blanding, the disagreeable features of Jonah Road are soon forgotten.
The reader who has heard the loud crashing of a small 1 kilowatt spark transmitter on board a ship, no doubt would expect to be greeted with an almost deafening roar as 200 kilowatts of energy were hurled into the massive antenna and thence across the seas. This is not the case at Radio Central; merely the steady hum of the generator such as can be heard at any lighting power station. First appearances strike one as being commonplace and uninteresting. No undue noise, no excitement, nothing dramatic; surely this cannot be the transmitter of the greatest wireless station in the world! This quiet, businesslike way of doing miraculous things, soon becomes a source of wonderment and admiration in itself. It is the characteristic way that the Radio Corporation has of doing things.
The Big Alternators.--The first objects that attract attention are the two 200 kilowatt, high-frequency Alexanderson alternators (see Fig. 178), which make this whole system of trans-Atlantic radio telegraphy possible. One is in operation, and the other is held in reserve for the second antenna now nearing completion. These generators produce 100 amperes of current at 2,000 volts, with a frequency of 18,000 cycles. From the generator, the current goes into a high-frequency air core transformer where the voltage is stepped up to 7,000 volts. From here, the current is led out of the power house to an immense helix or tuning coil (see Fig. 174), to which is attached the lead-in of the antenna. At the second, third, fourth, fifth, and sixth towers, leads are taken from the antenna and led to the ground through similar tuning coils. Such an arrangement is called a multiple-tuned antenna. It distributes the energy throughout the entire antenna system with a minimum of loss. Fig. 175 shows a schematic diagram of the antenna system, as it will be when completed.
All the transmission from Radio Central is done through New York, at 64 Broad Street. Here are the automatic tape transmitters, as well as the ordinary hand keys. The messages are sent by relay over a land line to Radio Central, where they automatically operate a relay which in turn controls three other relays, two of which control the power compensation, and the third controls the magnetic modulator which sends out the dots and dashes.
The magnetic modulator is inductively coupled to the high-frequency alternators through the air-core transformer, before mentioned. The modulator consists of two coils of wire on an iron core. Through one coil is passed the high-frequency alternating current. Through the other, is passed a direct current. The amount of direct current that flows through the coil of the modulator is so fixed that the impedance of the circuit prevents the passage of the high-frequency current into the antenna. By reducing the direct current, the impedance is reduced, and consequently less resistance is offered to the high-frequency current, and a larger amount flows into the antenna.
It requires but a comparatively small amount of direct current to effect a large amount of high-frequency current, so that the current going into the antenna can be easily controlled by a relay. When the key in New York is depressed, the direct current in the modulator is reduced, and 100 amperes of high-frequency current is put into the aerial. When the key is released, the relay causes the direct current to flow into the modulator, increasing the impedance and reducing the high-frequency current to about 3 amperes.
The sudden load that is put upon the alternator whenever the key is depressed is taken care of through power compensation by means of saturation coils all controlled by relays at the moment of pressing the key in New York. Mr. Blanding demonstrated the ease with which these large variances in current were handled, by switching the transmitter control from the New York relays, and by closing a small key, such as amateurs might use on spark coils, impressed 100 amperes into the antenna circuit. Due to the multiple-tuned antenna, 700 amperes are thus radiated.
Removing Sleet from Antenna.--One of the most interesting features of the station is the method by which sleet, that might form on the 25 miles of aerial wire in each aerial, is removed. With an antenna of such magnitude, the question of sleet on the wires is serious. This is taken care of by passing a current of 250 amperes at 1,500 volts through the antenna wires. Sufficient heat is generated to melt even the most severe ice formations on the wires in ten minutes. Small high-capacity condensers are connected in series with the antenna and tuning coils, to prevent the heat producing current from becoming grounded. The condensers have sufficient resistance to the 60 cycle current used for the above purpose, but readily allow the high-frequency current of the transmitter to pass through.
As before mentioned, the control of this station is entirely in the office at 64 Broad Street, New York, where not only the messages from Radio Central are sent, but also the messages from all the transmitting stations of the Radio Corporation on the Atlantic Coast. The high-powered transmitters at Tuckerton, N. J., New Brunswick, N. J., and Chatham, Mass., are directly controlled from the New York office.
Radio Central is not yet completed, there being only two of the proposed twelve antennæ erected. When completed, the twelve directive antennæ will be capable of being operated simultaneously with twelve different countries. Should, for any reason, additional power be required than that which can be radiated from each antenna separately, any desired number of antennæ will be connected together and a total of 2,400 kilowatts of energy could be radiated! As the Radio Corporation has thus far had no trouble in carrying on its European traffic with 200 kilowatts, the necessity of using additional power for that service is remote, but it is possible that when the South American service is inaugurated, additional power may then be necessary.
The Receiving Station.--The receiving part of Radio Central is located at Riverhead, Long Island, seventeen miles from the transmitter at Rocky Point. At Riverhead, not only is the receiving done for Radio Central transmitters, but also all the other trans-Atlantic receiving for the Radio Corporation. The actual translating of the code messages is done at 64 Broad Street, the Riverhead station merely tuning in the European stations and then automatically sending the signals over land lines to New York.
There are many novel features at the receiving station. The house in which the receiving is done is but a small cottage situated in the woods. The casual passerby would hardly notice it and surely would never suspect that one fifth of the trade of the United States with Europe is practically conducted in this little cottage. The uninitiated would also be considerably perplexed to find the antenna.
The antenna is nine miles long and only thirty feet high, and is carried on telegraph poles, so that one is apt to mistake it for an ordinary telephone line. This type of antenna is called a wave antenna. It is highly directional and eliminates a large amount of static. So efficient is it, that during the nine months that it has been in operation, there has not been a single moment when the Service had to be suspended. The receivers can even be operated during thunderstorms.
The wave antenna is the same length as the waves sent out by the Radio Station at Carnarvon, Wales, 14,000 meters. The waves coming in from European stations are picked up by the wave antenna which is pointed in their direction. An oscillating current is set up in the antenna which is transformed at the farther end of the antenna by a special form of transformer. The current then returns over the nine miles of antenna to the receiving instruments. For this purpose, the antenna acts as a transmission line. The powerful oscillations that come from the transmitting station at Rocky Point, seventeen miles away, come to the antenna from the opposite direction to those which come from the European stations. These oscillations are balanced out through the transformer at the far end of the antenna and do not reach the receiving apparatus.
The wave antenna, being aperiodic, is capable of being used for receiving more than one station at a time. All the trans-Atlantic traffic of the Radio Corporation is received over this one antenna. At the present time, there are four receiving sets in operation, although the receiving house is built to handle nine complete receivers for nine different stations. The present outfits receive from Carnarvon, Stavanger, Nauen and Bordeaux.
The four receivers are all of the same type. (See Fig. 180.) The incoming oscillations are received in circuits corresponding to their respective wave lengths and then, by a complex system of "traps," are purified of all unwanted signals, including most of the static disturbances. They are then passed through three stages of radio-frequency amplification, then rectified by means of a special two-element vacuum tube which is part of what is called a synchronous detector, and finally through two stages of audio-frequency amplification, from which point the message is transmitted over the land lines where it is either received through the usual telephones or, if the message is being sent at a greater rate than 30 words per minute, it is received on a tape by machine. These messages are sometimes handled at the speed of one hundred words per minute.
Mr. Tyrell, the Acting Chief of the station, was kind enough to connect his receiving machine, which he had at the station for emergency purposes, to the receiver and let the author see the messages from Carnarvon being received. The little pen which jigs up and down on the tape marking off the dots and dashes is being moved by someone three thousand miles across the ocean and as you watch this little device, which is being controlled by a human being so far away, you cannot help feeling strong admiration for those master minds that fathomed these natural secrets for the benefit of mankind.
When the telephones were connected to the receiving sets, the signals came in so loud that they could be heard all over the room and the signals from Stavanger, Norway, 4,000 miles away were too loud to be able to keep the telephones on the ears with comfort. None of these experiments, in any way, interfered with the regular receiving of the messages in New York. The operators in attendance in Riverhead test the signals from time to time to see that everything is O.K. and when the static becomes a little too strong, they make the necessary adjustments of the traps to minimize it. The static never prevents the reception of messages, although when it becomes very severe, it is necessary for the European station to be requested to send a little more slowly.
If the operator in New York finds that the static is getting bad, he advises Riverhead over the land line wire to tune it out, if possible. If this cannot be done, the New York operator then advises the transmitting operator in the same office in New York to advise the European station to send somewhat slower. The European operator receives these instructions and sends them over a land line to the transmitting station where they are received and followed. All this is a matter of but a few moments.
The practicality and efficiency of the whole system is amazing. It operates year in and year out, twenty-four hours per day without any interruption. Business men say that the service is equal in every way to the cables and in some cases better, particularly where there are no direct cables.
In his visit to the radio central transmitting and receiving station, the author came across a rather interesting bit of local color, which is perhaps peculiar to radio alone.
Diversion of a Radio Engineer.--In nearly all lines of business, when business hours are over, the individual seeks something totally different as a means of relaxation. While wandering around the radio station at Rocky Point, the author noticed a small aerial running from the Community House, where the engineers are quartered, to a small mast, some 150 feet away. On inquiring what this was, he was told that after watches, the engineers listen in on their own radio apparatus to the broadcasting stations and other types of radio traffic. One would think that after many hours spent on duty in the most powerful radio station of the world, the engineers would be glad to forget, at least for the time being, that such a business as radio existed.
At the receiving station at Riverhead, they go to an even greater extreme. About 200 yards from the receiving house, Mr. Tyrell and his associates have installed a complete amateur continuous wave station. All spare moments of the various operators of the receiving station are spent at their own amateur apparatus. Naturally, with such engineers as those caring for all the trans-Atlantic receiving apparatus of the Radio Corporation, a very efficient and modern amateur station can be expected.
Interchanges of messages between their station, call letters of which are 2BML and 2EH, and points as far distant as Oklahoma City, Okla., have been had, and this station also was one of the first whose signals reached across the Atlantic during the tests between the United States and Ardrossan, Scotland. Mr. Tyrell, however, is not satisfied to spend his spare time during the day at this amateur station, but when he goes home he takes great pleasure in operating a receiving station that he has installed for the amusement of his family. At this station, he particularly picks up broadcasting stations and supplies the family with various forms of entertainment.
As before stated, there is perhaps no profession in which such interest is taken. Many of the ship operators have their own radio stations at home, and they make it their business, immediately after arriving at home from a long sea voyage, to rush off to their apparatus and commence to send and receive messages for their own amusement.
The author has again and again seen operators on board ship connect up an extra pair of telephones, after their watch is done, and listen in with the operator then on watch, for hours, in addition to the time actually required of them.