US1694646A - Wireless telegraph receiver - Google Patents

Description

Dec. 11, 1928. 1,694,646

c. s. FRANKLIN WIRELESS TELEGRAPH RECEIVER Original Filed June 25, 1919 Patented Dec. 11,1928.

A I UNITED STATES PATENT orrlcs,

CHARLES SAMUEL FRANKLIN, LONDON, ENGLAND, ASSIGNOR, BY MESNE ASSIGN- MENTS, TO RADIO CORPORATION OF AMERICA, AOORPORATION OF DELAWARE.

WIRELESS TELEGRAPH RECEIVER:

Application filed June 25, 1919, Serial No. 306,608, and in Grpat 'Britain June 28, 1928. Renewed October This invention relates to improved circuits for wireless telegraph receivers, and is particularly applicable for receivers for waves of a few metres. g

In receivers employing thermionic devices it is usual to connect the secondary circuit of the receiving transformer between the grid and filament of a valve of the three electrode type, or between the anode and filament of l a valve of the two electrode type As the capacity at the filament end of the secondary is large (owing to the batteries, accessories and leads required) compared with the capacity at the grid or anode end, the variations of potential produced across the'secondary by the received waves cause a" greater variation in the potential of the grid 01' anode relatively to the surroundings than in the potential of the filament.

It has now been found that by arranging the circuit so that the potential of the filament rather than the potential of the grid or an'ode is varied relatively to its surroundings, a valve receiver is made many times more sensitive for short waves.

To obtain this efiect it is necessary so to arrange the circuit that the capacity at the filament endof the secondary is a mlnimum. This may be efiected by connecting the lighting battery to the filamentthrough long chok: ing coils; the capacity of the lighting bat tery and accessories does not then materially affect the capacity at the filament end of the secondary. It is preferred, however, to cause 5 the secondary directly to affect the potential of the filament by connecting the-seco'ndary directly in theleads to the filament. As two wires must be employed between the battery and the filament, the secondary is 4 wound with two wires laid together on the same former, the two wires being connected at one end of the coil to the filament and at the other end, preferably through long choking coils, to the heating battery and ac- J cessories. A tuning condenser is connected in parallel with the secondary; this is preferably arranged in two equal parts each connected in parallel with one of the secondary wires. The telephone or indicator may be connected in series with an adjustable battery.

and choking coil between the anode and the --filament lighting battery.

The invention 15 illustrated by the accompanymg diagram, in'which 1 is a valve having a filament 2 and an anode 3. 4 is a secondary coupled to a primary-5 in an aerial circuit and consisting of'two wires wound together on" a former and connected at one'end to the filament 2 and to tuning condensers 6, 7, and at the other end to choke coils 8, 9, to the condensers 6, 7, and to fixed condensers 10, 11. The coils 8, 9, .areconnected at one end to a resistance 12 and a battery 13 which heats the filament 2, and at the other end to the condensers 6, 7. 1 1 is a third choke coil connected at one end to the condensers 10, 11, and to the anode 3, and at the other end through the primary 15 of a transformer of which the secondary 16 is connected to a telephone 17, to the positive of a battery 18 of adjustable voltage, the negative of which is connected to the heating battery 13. The secondary circuit comprising the-coil f and condensers 6 and 7, is tuned to the wave received. 1 The choking coils 8, 9, 14, are not essential, but they are particularly useful in the case of short waves in preventing the oscillations picked up by the telephone and battery wires 30 from affecting the secondary circuit. It will be noticed hat thefilament 2 is con-' nected solely tothe secondary circuit, while the anode 3 isconnected'to the coils 8, 9 and 14, and the battery leads besides being con .nected to the secondary; consequently the capacity of 3 relatively to its surroundings will be greater than that of 2. 7 It follows that when anydiiference-of potential is produced between 2 and 3 by the secondary, the v'ariation of potential of 2 relative. to its surroundings will be greater-than that of 3.

What I claim is h 1. 'A circuit comprising a transformer having a coil consisting'of two conductors wound together and insulated from each other, a thermionic valve having a filament and a. 7 cold electrode, each conductorof the coil being connected at one end-of the coil to opposite leads respectively of the filament, and a battery connected to the filament through said conductors. p v

2. A circuit comprising "a transformer, a thermionic valve hav' g a filament and a cold electrode connected t rough a circuit including a coil of the transformer and a condenser,

a source of space current for said valve, a source of current for heating the filament, andf means between the sources of current and the filament for neutralizing the capacity effect of said sources of current and their associated connections on the filament end of the coil whereby: the variation of potential at said end, when oscillations are impressed on the coil,

is increased. 7 1

3. A circuit comprising a transformer, a thermionic valve having a filament and a cold in electrode coupled by a circuit whichincludes the transformer coil and another circuit con-' nectingjsaid filament and" cold electrode and containing a source of current, a. second source of current for heating the filament and in- 1 ductances between the sources of current and filament for neutralizing capacity effect of said sources of current and their associated connections on the filament end of the coil whereby the potential at said end varies be tween a minimum and a maximum relative to 3 its surroundings when oscillations are impressed on the secondary. 4. A circuit comprising a first inductance, a thermionic valvevhaving a filament and a cold electrode connected to each other through a circuit including the first inductance and through another circuit containing a source" of current, a second source of current for heating the filament, and a second inductance ,be tween the second source of current and the filament.

5. A circuit comprising a transformer hav-.

ing a coil consisting of two conductors wound together and insulated from each other, a

thermionic valve having a. filament and a cold electrode, each conductor of the coil being connected at one end of the coil to opposite leads res ctively of the filament, the other ends of t i e conductors being separately 40 capac'itively coupled to the cold electrode, and

attery connected-to the filament through 2 i the coil. A

i 6. A circuit comprising a transformer having a coil consistin of two conductors wound together and insu ated from each other, a thermionic valve having a filament and a cold electrode, each-conductor of the coil beingconnected at one end of the coil to oppositeI leads respectivel of the filament, the other ends of the con uctors being separately capacitively coupled to the cold electrode, a battery connected to the filament through leads containing inductance, a circuit connecting the filament and cold electrode containing a 65 battery and inductances in the connections of said circuit between the filament and cold electrode.

7 A circuit comprising a transformer having a coil consisting of two inductances and insulated from each other, a thermionic valve having a filament and a cold electrode, each "inductance of the coil being connected at one end of the coil to opposite leads respectively of the filament, the other ends of-the inductances being connected in circuit with the cold electrode, and aJbat-tery for heating the filament connect-ed thereto through the inductances.

8. A circuit comprising a transformer havconductor of the coil being connected at one end of the coil to opposite leads respectively of the filament and the other ends of the conductors connected to the cold electrode through a pair of condensers, and a battery for'heating the filament connected thereto.

9. The combination with an electron emission tube filament which is not at the radio frequency potential of the general surroundingsyand a filament heating source which is at substantially the radio frequency potential of the general surroundings of a pair of impedances arranged in series with respect to the filament heating current, and in parallel with respect to the radio frequency current for overcoming the potential difference between the source and the filament. I

l().- In combination, an electron emission tube having a filament which is not at the potential of the general surroundings, a ra- (llO frequency circuit assoclated therewith, a

sourceof filament heating current which is radio frequencycircuit in parallel for the radio frequency current and in series for the filament heating current, said impedances being of proper magnitude to overcome the potential diflerence between the filament and the source.

11. An electron tube circuit comprising an electron emission tube having a filament which is not at the potential of the general surroundings and at least one other electrode, a radio frequency circuit including a coupling inductance connected between said electrodes, a source of filament heating current, said source being at substantially the potential of the general surroundings, and means connecting said source to said filament comprising the coupling inductance and another impedance in arallel therewith for overcoming the di erence'in potential between the filament and the general surroundings.

12. An electron tube circuit c'om rising an electron emission tube having a lament. which is not atthe potential of the general surroundings and at least one other electrode, a radio frequency circuit comprising a tuning inductance and a tuning condenser connected between said electrodes, a source of filament heating current, said source being at substantially the potential of the general surroundings, and means connecting said source to said filament comprising the tuning inductance and another impedance in parallel therewith for overcoming the difference in potential between the filament and the general surroundings.

13. An electron tube circuit comprising an electron emission tube having a filament which is not at the potential of the general surroundings and at least one other'electrode, a radio frequency circuit including an impedance connected between said electrodes, a source of electrical energy for heating said filament, saidsource being at'substantially the potential of the general surroundings, aiml a pair of leads connecting said source to the filament, each lead including a portion of the said-impedance in order to overcome thepotential difference between the filament and the source.

14.. In combination, an electron emission tube having a hot and a cold electrode, a radio frequency circuitfconnected therebetween, a pair of inductances in said circuit arranged in parallel with respect to the radio freuency current, asource of. energy for heating t e hot electrode, and means connecting the 'hot electrode and the source comprising said pair of inductances arranged in series wlth respect to current from the source.

15. In combination, an electron emission tube having a hot cathode and an anode, a radio frequency circuit therebetween, a source of cathode heating current, said source 'being series with respect to the filament heating,

current for overcoming the potential differencebetween the source and the filament, whereby the radio frequency potential fluctuations take place substantially on the cathode. r

16. In combination, an electron emission tube-having a hot cathode which is'not at the radio frequency potential of the general surroundings, and an anode which is at substantially the radio frequency potential of the general surroundings, a radio frequency circuit therebetween, a source of cathode heating current which is at substantially the potential of the general surroundings, and a pair of radio frequency impedances in said circuit and arranged in series with respect to the filament heating current and in parallel with respect to theradio frequency current for overcoming the otential difference between the source and t e filament. I

In testimony that I claim the foregoing as my invention I have signed my name this 13th day of J one, 1919.

o CHARLES SAMUEL FRANKLIN.

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