US2423836A - Ultra high frequency communication system - Google Patents

Description

July 15, 1947. G ETAL 2,423,836

ULTRA-HIGH FREQUENCY COMMUNICATION SYSTEM Filed Feb. 11, 1936 4 Sheets-Sheet l P LEI] INVENTOR BURTON G. LAKE WILLIAM C. EDDY ATTO R N EY July 15,1947. B. e. LAKE ETAL ULTRA-:HIGH FREQUENCY COMMUNICATION SYSTEM Filed Feb. 11, 1936 4 Sheets-Sheet 2 4 co pucToR- CABLE CONDUCTOR CABL E INVENTORS BURTON G. LAKE WILLIAM..C.EDDY

TRAfSMlT RECEIVE ATTORNEY July 15, 1947. B. G. LAKE ETAL ,8

' ULTRA-HIGH FREQUENCY COMMUNICATION SYSTEM I Filed Feb. 11, 1936 4 Sheets-Sheet 3 MODULATOR &

POWER AMPLIFIER UNITS UNIT INVENTOR BURTON G. LAKE WILLIAM C-EDDY ATTORNEY July 15, 1947. B. G. LAKE ETAL ULTRA-HIGH FREQUENCY COMMUNICATION SYSTEM Filed Feb. 11, 1936 4 Sheets-Sheet 4 mvzufok BURTON e. LAKE WILLIAM C. EDDY M ATTORNEY Patented July 15, 1947 ULTRA HIGH FREQUENCY COMMUNICATION SYSTEM Burton G. Lake and William C. Eddy, United States Navy Application February 11, 1936, Serial No. 63,308

(Granted under the act of March 3, 1883, as

8 Claims.

This invention relates to radio transmittin and receiving circuits operated at frequencies greater than 100 megacycles or at wavelengths of less than three meters.

The principal object of this invention is to make possible the exchange of ultra-high frequency radio signals between two stations or operating locations so placed that an exchange of such signals by the usual apparatus and methods is impossible.

It relates particularly to the exchange of such signals between two submerged submarines or between a submerged submarine and any other station equipped to receive and transmit these signals. This communication may be accomplished without exposing more of the submarine than that ordinarily exposed in routine submerged operations. An added advantage lies in the fact that efficient communication may be car ried on without disclosing the position of the submerged submarine to the ship or station with which it is communicating, or any other station. A further advantage of this invention lies in the comparative secrecy of the communications as compared with communication at lower frequencies, which may travel great distances due to reflection and refraction from the Heaviside layer. It appears that this reflection or refraction does not take place if the frequency is greater than about 100 megacycles and also that the range of such waves is practically limited to the quasi-optical range between the transmitter and receiver unless relatively high power is used. In carrying out our invention we use relatively low power which limits the range of our communication to quasi-optical distances in the present state of the art of communication at ultra-high frequencies above 100' megacycles.

This system also makes possible ultra-high frequency radio communication between totally submerged submarines or between totally submerged submarines and surface ships or stations when used in conjunction with a small buoy floated to the surface from the submarine and attached thereto by waterproof conductors.

In general, this system, which will be described in detail in the following pages, makes possible successful ultra-high frequency radio communication between two operators under conditions where the operators and the major portion of the apparatus are so located that they are completely shielded from each other for ultra-high frequency communication.

In the development of this system of communication we have found that, at ultra-high amended April 30, 1928; 3'70 0. G. 757) frequencies, it is impracticable to transmit or receive signals from an antenna located above water by connecting it to the transmitting and receiving equipment with a conductor passing through the water, even though the conductor and antenna be insulated from direct contact with the water. The great absorption from the conductor in passing through the water prohibits the transfer of any appreciable amount of radio energy either for transmitting or receiving. In other Words, it is impracticable to transfer ultrahigh frequency radio energy through a conductor if the conductor is in close proximity to water or other absorbing medium.

We have eliminated the necessity for such a conductor carrying ultra-high frequencies by 10- cating at the antenna, above water or clear of the absorbing medium, a generator of the ultrahigh frequency waves to be transmitted and a detector of the ultra-high frequency waves to be received. This combination transmitter-receiver is connected by means of suitable insulated conductors to the remainder of the apparatus which may be located at the point of actual transmission or reception of voice or other signals. Voice signals are preferably used. By this method the conductors which pass through the water carry only audio or voice frequencies and power and do not carry ultra-high frequency radio energy during either transmission or reception. The absorption effect previously mentioned does not occur at these audio frequencies. The length of these conductors which connect the transmitterreceiver with the remainder of the apparatus is limited only by the practicability of transmitting over them a super-audible or very low radio frequency for obtaining a super-regenerative effect in the transmitter-receiver during reception. Tests indicate that this low radio frequency is not absorbed appreciably with conductor lengths up to 300 feet. If the super-regenerative type of detection is not used the length of the conductors is limited only by the practicability of transmitting over them voice frequencies and power. The present invention will be more readily understood by reference to. the following detailed description taken in connection with the accompanying drawings.

In the drawings:

Fig. 1 is an external view of the transmitterreceiver unit;

Fig. 2 is a sectional View of the transmitter"- receiver unit;

Fig. 3 is a diagram of the electrical circuits of the complete ultra-high frequency transmitting and receiving system;

Fig.4 shows the arrangement of the complete system as installed on board a submarine, including the transmitter-receiver unit mounted on the submarine periscope and/or in a buoy;

Fig. 5 shows the details of the remotely controlled tuning arrangement used in the transmitter-receiver unit; and

Fig. 6 shows the details of the transfer switch and interlock used in shifting from transmit to receive or vice-versa.

Referring to Figs. 1 and 2, the form and meohanical details of the transmitter-receiver unit are shown. This is the unit of the system which must be located at a point favorable for the transmission and reception of ultra-high frequency waves, i, e., clear of absorbing medium and, in the case of a submarine, is located at the top of the periscope or in a buoy on the surface of the water. The antenna 8 must be clear of the water during operation. This transmitter-receiver unit consists essentially of a vacuum tube and associated circuits suitably coupled to a resonant antenna and inclosed in a watertight container. This vacuum tube operates as a generator of ultra-high frequency power when transmitting and as a detector of ultra-high frequency waves when receiving. The power to operate the vacuum tube for both transmitting and receiving is supplied through the four-conductor cable II which also carries the modulating frequency or voice currents and the current for operating the sole noid II). The frequency at which we preferably operate the system is about 175 inegacycles. This frequency makes it practicable to use a half-wave or Hertzian antenna of short length (approximately 28 inches) which is voltage fed from the lower end by the electrostatic coupling between the cap 3 and the plate of the vacuum tube 6. This frequency permits the use of a short rigid antenna of favorable physical dimensions which is also very efiicient electrically. The antenna is mounted in the insulator 2 as shown in Fig. 2.

This frequency also permits the use of a regenerative circuit for the generation and reception of ultra-high frequency waves at 165 megacycles with good efficiency and is used in preference to an electronic circuit of the Barkhausen-Kurtz form, or other electronic oscillator.

In Figs. 1, 2, and 3, I is the half-wave vertical antenna, 2 is the insulator, 3 is the antenna coupling cap, 4 is the vacuum tube oscillator and detector, 5 is the cathode bias resistor, 6 is the variable dielectric tunin condenser, l is the fixed inductance of the oscillating circuit, 8 is the watertight container of insulating material, 9 is the plate circuit radio frequency choke, I is the tuning solenoid coil, II is the four-conductor cable, I2 is the watertight gland or stufling box, I3 is the filament short circuiting condenser, I4 is a .center tapped resistance connected between the filament leads, I is the grid circuit radio frequency choke, I6 is the grid-plate by-pass condenser, IT is the tuning solenoid plunger spring, I8 is the solenoid plunger, I9 is the external part of the watertight gland or stuffin box.

If this vacuum tube and circuit are to be used for both generating and detecting ultra-high frequency radio waves, it is obvious that a suitable type of tube must be used. The type-56 receiving tube which has a relatively high amplification factor (13.8) for a three-element tube and operates well as an oscillator or detection at 1'75 megaoycles has been found to be suitable. It also has the advantage that alternating current may be used to heat the cathode and we have found that this tube will dissipate a considerable amount of power at the plate without over-heating. However, othertypes of tubes may be used providing the inter-electrode capacities are not so high as to make practicable the design of a regenerative circuit at ultra-high frequency. We have also discovered that this type of circuit (the so called ultra-audion) will usually generate an audible or super-audible frequency in addition to the ultra-high frequency and will thus modulate theultra-high frequency at some undesired frequency unless special precautions are taken. To avoid this we use a cathode bias oscillator in which the cathode resistor is not by-passed by a condenser. With this type of circuit we operate this tube with 400 volts on. the plate and with a plate current of 4:0 milliamperes. Experiments have shown that the tube will not operate with this input power as a grid leak oscillator, apparently because secondary emission from the grid reduces the normal grid current through the grid leak from which the operating bias is obtained as a grid leak oscillator and the plate current rises to very high values. Although the tube is not biased for efficient detection we have found that by. using super-regeneration it acts as a reasonably efficient super-regenerative detector. It is obvious that, with the cathode resistor 5 not icy-passed for audio frequencies, there is a certain amount of degenerative action at audio frequencies. However, it appears that this degenerative action does not interfere seriously with modulation as a transmitter or detection as a receiver because the value of the resistor is relatively low (about 1600 ohms). The filament short circuiting condenser I3 short circuits the filament leads for radio frequencies and tends to prevent the loss of ultra-high frequency power in the cable II. The radio frequency chokes 9 and i5 also operate to prevent losses in the cable.

The tuning arrangement, which is in use duh ing reception only, consists of the condenser ii which has two stationary plates, connected in the I circuit as shown in Fig. 3, and a movable dielectric 20 of glass or other suitable material between the plates. This glass dielectric it is secured to the solenoid plunger 1 8 and moves with it. When the solenoid winding If! is not energized the spring i1 holds the glass plate between the condenser plates and the capacity of the condenser is maximum and is determined by the size of the plates and the dielectric constant of the glass plate. The solenoid is not energized during transmission.

During reception, by means of a switch 25 and rheostat 21 shown in Fig, 3, the solenoid is energized and withdraws the glass dielectric from between the condenser plates a certain amount depending on the setting of rheostat 27!, thus reducing the capacity of the condenser and tuning the regenerative circuit. We have found that in this circuit the capacity of condenser 6 must always be decreased to tune the circuit to receive the same frequency it generates as a transmitter. This because the frequency at which the circuit regenerates depends somewhat on the plate volt age, the frequency increasing as the plate volt age is increased. A much higher voltage is used for transmitting than is used for receiving, there" fore the condenser E is always set at maximum capacity by the spring I! during transmission and the capacity is reduced during reception to the required amount by energizing the solenoid II] through the variable rheostat 27. This variable rheostat is the remote tuning control of the transrmtter-receiver unit. Alternating current i preferably used to operate the solenoid l0 and the same transformer winding is used for both the solenoid winding and the .oscillator filaments. The solenoid and spring I! are so designed as to operate at 2.5 volts A. C. which is the voltage required for the filaments of the vacuum tube 4..- This transformer Winding must supply suificient voltage to overcome the voltage drop in cable H and, of course, this depends on the length of the cable, and the size of the Wires composing it. We have found that the use of alternating current in solenoid It results in smoother and more positive action in tuning than the use of direct current. Any tendency toward vibration of the plunger l8 and glass dielectric is eliminated by a coating of light insulating oil between the glass plate 20 and the condenser plates.

The four-conductor cable I l is connected as shown in Fig. 3 to the transmitter-receiver unit. 2! is the high voltage plate lead. 22 is a connection to the tube filament. 23 is a connection to the other side of the tube filament and one side of the solenoid coil and carries both filament and solenoid current. 24 is the side of the solenoid coil in which the switch 26 and tuning rheostat 2'! are connected. The plate current of vacuum tube 4 is returned to Bethrough the filament leads by means of the center-tapped resis tors M and 2-5.

The switch 26 shown diagrammatically in Fig. 3 and in detail in Fig. 6 is used to shift from transmit to receive and in conjunction with the interlocking control for the variable rheostat makes it possible to break the high voltage power supply to the oscillator 4 and modulator 29 through modulator choke 30 until the current flow has been reduced to a low value by intro-v ducing the full value of resistance of rheostat 28: in the circuit. Unless this current is reduced to a low value before switch .28 is thrown from the transmit to receive position the inductance of choke 30 will cause very high voltages to be induced in the system, resulting in breaking down insulation and condensers.

A stage of speech amplification is introduced between the modulator tube 29 and the micro-- phone as shown in Fig. 3. The power unit 31 is. preferably built as a separate unit and connected to the other apparatus consisting of modulator, speech amplifier, audio amplifier and associated circuits by a short length of six-conductor cable about three feet in length to avoid hum during reception caused by induction from the.power'al3- paratus.

The full voltage output of the power unit 3| is applied to the modulator and oscillator tubes through modulator choke 30 when switch 26 is in the transmit position and the rheostat 28 turned to the locked position with all resistance out of the circuit.

When receiving, the switch 26' is thrown to the receive position, which connects the output of vacuum tube 4 to the input circuit of a twostage audio amplifier as shown in Fig. 3.. This e also connects the tuning solenoid ID in the circuit and permits tuning during reception as previously explained. 32 and 33; are the audio am' plifier tubes used for reception. 34.. is the superregenerativeoscillator which supplies the super audible modulating frequency to, vacuum. tube; 4.

age through variable rheostat 35. In order to prevent blocking of audio amplifier tube 32 by the super-regenerator oscillator 34 a condenser 36 of suitable capacity is connected between the control grid and ground of this tube which effectively grounds the grid for the super-regenerator frequency but does not ground it for audio frequencies. A resistor 3! of suitable value is also connected from grid to ground to prevent audio oscillation in the amplifier.

It will be understood that the above description and accompanying drawings comprehend only the general and preferred embodiment of this invention and that various changes in the construction, proportions, and arrangement of parts, may be made within the scope of the appended claims, and without sacrificing any of the advantages of the invention.

invention may be manufactured and used by or for the Government of the United States for governmental purposes without the payment of any royalties thereon or therefor.

We claim:

1. In a remotely controlled ultra-high frequency radio transmission system, a thermionic tube having a cathode, an anode, and a control electrode, said tube being located at a point favorable for the transmission of ultra-high frequency radio energy, a control station located at so a. point where transmission of ultra-high frequency radio energy is impossible, a control cable tube from said source of cathode potential, means comprising one of the conductors of said cable 451 for applying potential to the anode of said tube from said source of anode potential, an ultra; high frequency resonant circuit connecting the cathode, anode, and control electrode of said tube,- for generating and sustaining oscillations therein, means operable from said control station to, change the frequency of resonance of said resonant circuit for reception, a half wave antenna capacitively coupled to the, anode of said tube, and means located at said control station for varying the anode current in said tube in accordance with a signal.

2. In a remotely controlled ultra-high frequency radio receiving system, a thermionic tube having a cathode, an anode, and a control electrode, said tube bein located at a point favorable for the reception of ultra-high frequency radio energy, a control station located at a point where reception of ultra-high frequency radio energy is impossible, a control cable having at least four, conductors extending from said control. station to said tube, a source of cathode potential and a source of anode potential at said control station, means comprising two of the conductors of. said cable for energizing the cathode of said, tube from said source of cathode potential, means including one of the conductors of said cable for applyin potential to the; anode of said, tube from said source of anode potential, an ultra-highfrequency resonant circuit connecting the cathode, anode, and control electrode of said tube for generating and sustaining oscillations, therein when appropriate potentials are applied to. the electrodes of said tube,v a half Wave antenna, capacitively coupled to the anode of said tube, means for varying the potential applied to the anode of said tube at a super-audible frequency for causing said tube to operate as a super-regenerative detector of the ultra-high frequency energy in said antenna, means operable from said control station to change the frequency of resonance of said resonant circuit for reception, and means located at said control station coupled to said super-regenerative detector by way of two of the conductors of said cable for amplifying the detected component of anode circuit energy.

3. In a remotely controlled ultra-high frequency radio receiving system, a thermionic tube having a cathode, an anode, and a control electrode, said tube being located at a point favorable for the reception of ultra-high frequency radio energy, a control station located at a point where reception of ultra-high frequency radio energy i impossible, a control cable having at least four conductors extending from said control station to said tube, a source of cathode potential and a source of anode potential at said control station, means comprising two of the conductors of said cable for energizing the cathode of said tube from said source of cathode potential, means including one of the conductors of said cable for applying potential to the anode of said tube from said source of anode potential, an ultra-high frequency resonant circuit connecting the oathode, anode, and control electrode of said tube for generating and sustaining oscillations therein when appropriate potentials are applied to the electrodes of said tube, a half wave antenna capacitively coupled to the anode of said tube, means for varying the potential applied to the anode of said tube at a uper-audible frequency for causing said tube to operate as a superregenerative detector of the ultra-high frequency energy in said antenna, means located at said control station coupled to said super-regenerative detector by way of two of the conductors of said cable for amplifying the detected component of anode circuit energy, means comprising a variable condenser and a solenoid for controlling said condenser at the said point favorable for the reception of ultra-high frequency energy, said condenser constituting a portion of said resonant circuit, and means for controlling the current in said solenoid from said control station over one of conductors of said cable connected to the cathode of said tube and another of said conductors not connected to said tube.

4. An ultra-high frequency radio transmitter and receiver located at a transmitting and receiving station favorable for the transmission and reception of ultra-high frequency radio energy, a control cable having at least four conductors extending from said station to a submerged station, a thermionic tube having a cathode, an anode, and a control electrode located at said transmitting and receiving station, a source of cathode potential and a source of anode potential at said submerged station, means comprising a first and second conductor of said control cable for energizin the cathode of said tube from said source of cathode potential, means comprising a third conductor of said control cable for applying potential to the anode of said tube, an ultra-high frequency resonant circuit including a variable condenser interconnecting the anode and control electrode of said tube for generating and sustaining oscillations therein when appropriate potentials are applied thereto, an antenna coupled to said resonant circuit, means located at said submerged station for varying the current in said third conductor in accordance with signals to be transmitted when it is desired to operate said system as a transmitter, a solenoid for controlling said variable condenser located at said transmitting and receiving station, means for applying potential to and controlling the current to said solenoid from said submerged station for controlling said condenser, said means including a fourth conductor of said cable, means located at said submerged station for controlling said condenser, said means includin a fourth conductor of said cable, and means located at said submerged station for varying the potential applied to the anode of said tube at a super-audible frequency for causing said tube to operate as a super-regenerative detector of the ultra-high frequency received by said antenna when it is desired to operate said system as a receiver.

5. An ultra-high frequency radio transmitter and receiver located at a transmitting and receiving station favorable for the transmission and reception of ultra-high frequency radio energy, a control cable having at least four conductors extending from said station to a submerged station, a thermionic tube having a cathode, an anode, and a control electrode located at said transmitting and receiving station, a source of cathode potential and a source of anode potential at said submerged station, means comprising a first and second conductor of said control cable for energizing the cathode of said tube from said source of cathode potential, means comprising a third conductor of said control cable for applying potential to the anode of said tube, an ultrahigh'frequency resonant circuit including a Variable condenser interconnecting the anode and control electrode of said tube for generating and sustaining oscillations therein when appropriate potentials are applied thereto, a half wave antenna coupled to said resonant circuit, means located at said submerged station for varying the current in said third conductor in accordance with signals to be transmitted when it is desired to operate said system as a transmitter, a solenoid for controlling said variable condenser located at said transmitting and receiving station, means for applying potential to and controlling the current in said solenoid from said submerged station for controlling said condenser, said means including a fourth conductor of said cable, means located at said submerged station for varying the potential applied to the anode of said tube at a super-audible frequency for causing said tube to operate as a super-regenerative detector of the ultra-high frequency received by said antenna when it is desired to operate said system as a receiver and a switch at said control station for selectively connecting said last means or said means for varying the current in said third conductor to said tube whereby said tube may be made to operate as a transmitter or receiver by way of said four conductor cable.

6. A system of ultra-high frequency'radio communication comprising an antenna, a vacuum tube combination transmitter-receiver in close proximity to said antenna and coupled thereto, said antenna and combination transmitterreceiver operating at ultra-high frequency and located at a point favorable for said operation; means for modulatin said transmitter at audio frequencies; remote control means for tuning said combination to one frequency for transmitting and to a different frequency for receiving; means for amplifying the output of said receiver at audible frequencies; said modulating and amplifying means being located at a point where the transmission and reception of ultra-high frequency waves is impossible; means for connecting said combination transmitter-receiver with said modulating and amplifying means for the transfer of audible r signalling frequencies and power between them.

7. In combination, an ultra-high frequency transmitter-receiver including a vacuum tube, a water-tight housing in which said transmitterreceiver is enclosed, a vertical half-wave antenna capacitively coupled at one end to said tube, audio modulating and amplifying means disposed at a station where ultra-high frequency transmission and reception are impossible and means connecting said transmitter-receiver to said modulating and amplifying means to transfer audio frequency between said station and said transmitterreceiver.

8. The method of operating an ultra-high frequency radio signal system that includes transceiver means for generating an ultra-high frequency carrier Wave and transmitting the same and for receiving and demodulating signals, all at a first location permitting these operations, and also including modulating means and audio signal output means at a second location where transmission and reception are impossible, comprising the steps of tuning said transceiver means from said second location to one frequency for transmitting, causin said transceiver to generate a carrier wave, impressing a signal modulation on said carrier wave from said second location,

tuning said'transceiver from said second location to a different frequency for reception, receiving and demodulating a signal bearing wave at said transceiver, and transferring audible frequency signals to said second location.

BURTON G. LAKE. WILLIAM C. EDDY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,962,611 Nyman June 12, 1934 1,811,357 Karplus June 23, 1931 1,656,987 Ohl 1- Jan. 24, 1928 1,806,245 Esau May 19, 1931 1,116,111 Pfund Nov. 3, 1914 1,641,946 Murray Sept. 6, 1927 1,940,228 Polydoroff Dec. 19, 1933 1,974,184 Haigis Sept. 18, 1934 FOREIGN PATENTS Number Country Date 347,865 Great Britain May 7, 1931 367,278 Great Britain May 19, 1931 OTHER REFERENCES A Radio Beacon and Receiving System for Blind Landing of Aircraft, Research paper #238, Bureau of Standards, vol. 5, Oct. 1930. Fig. 11 following page 910 and Fig. 33 on page 928.

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