US2143658A - Ultra short wave system - Google Patents

Description

Jan. 10, 1939. R. M. MORRIS ET AL 2,143,658

ULTRA SHORT WAVE SYSTEM Filed Sept. 50, 1936 2 Sheet-Sheet 1 INVENTOR R.M. MORRIS AND ATTORNEY Jan. W, 1939. I R. M. MORRIS ET AL 2,143,658

ULTRA SHORT WAVE SYSTEM Filed Sept. 50, 1936 I 2 Sheets-Sheet 2 [IIIITHII IIHUTUTI INVENTOR R. M. MORRIS AND C. P. SWEENY BY I ATTORNEY Patented Jan. 10, 1939 UNITED STATES PATENT OFFIC ULTRA SHORT WAVE SYSTEM Application September 30, 1936, Serial No. 103,289

6 Claims.

The present invention relates to ultra short wave communication systems, and has for its primary object to provide a highly portable construction which can be carried in the hand and is fairly rugged, for transmitting and/or receiving short waves of the order of one meter or less.

A further object is to provide such an improved construction which can serve in the laboratory or in the field as a source of test signals for various types of high frequency measurements.

A feature of the present invention lies in the excellent mechanicaland electrical design of the structure.

In the accompanying description of the drawmgs:

Fig. 1 illustrates an exploded view of the mechanical construction of applicants arrangement, except for the omission of the front panel;

Fig. 2 illustrates a plan view of the lower portion of Fig. 1 with the top removed;

Fig. 3 illustrates a cross-sectional view of Fig. 2 along the line 33; and

Fig. 4 shows the equivalent electrical circuit of applicants arrangement, together with the essential external circuit elements necessary to form a complete system.

Since the same elements throughout the figures are represented by the same reference characters, a better understanding of the invention will be had by first referring to Fig. 4 which shows the equivalent circuit arrangement. In this figure the antenna, used either for transmitting or receiving purposes, comprises a dipole having two arms I and 2, each electrically equivalent to a quarter wavelength and connected in series through a variable condenser 3 to one terminal of a parallel tuned circuit comprising a variable condenser 4 and an inductance 5. Coupled to inductance 5 and connected in the anode circuit of electron discharge device oscillator I is an inductance 6 which is connected at one terminal to the anode of the electron discharge device and at the other terminal to the cathode thereof through a by-pass condenser 8.

The anode circuit of the oscillator is tuned to the desired operating frequency by means of variable condenser ID connected between the anode and cathode of the electron discharge device oscillator I and in shunt with the coil 6. Similarly, the grid 28 of the oscillator is tuned to the desired operating frequency by variable condenser I I in shunt with coil I2, both of which are connected between the cathode and the grid of the tube. A high resistance 9 serves as a grid leak and is shunted by a portion of condenser 8, as shown in the drawings. For the production of oscillations in the circuit, feed back is obtained by means of the interelectrode capacity of the electron discharge device I. A suitable polarizing potential is applied to the anode through choke coil I3 which is connected in series to one winding of a transformer I4 which is located externally of applicants compact mechanical arrangement. By means of this arrangement oscillations were obtained of the order of 300 megacycles, with a maximum variation in frequency of approximately 1% or less, depending upon the percentage of modulation.

When it is desired to use the circuit as a transmitting device, a suitable level of modulation is applied, usually a very low percentage of modulation, to the external transformer I4 over the speech input circuit indicated in the drawings. On the other hand, if the circuit is to be used as a receiver, the speech input circuit will become the output circuit and the inductance coil 5 will then be coupled to coil I2 instead of to coil 6.

The practical embodiment of the invention is shown in the exploded view of Fig. 1 wherein the upper removable portion illustrates the antenna in the form of two arms I, 2, each of which are in series with a condenser 3, made variable by means of a screw 3' and coupled through connections extending through insulators to the.

parallel tuned circuit comprising condenser 4 and inductance 5. As will be seen, condenser 4 comprises two semi-circular plates which are connected to the terminals of 5, both plates in turn being electrostatically coupled to a larger circular plate whose distance from the two semicircular plates can be varied by means of threaded screw I5, with a consequent variation of the capacitance of the condenser 4. In practice, the inductance coil 5 comprises one-and-one-half turns of #18 copper wire in diameter for the frequency of 300 megacycles. The elements of the antenna I, 2, tuning condensers 3 and 4, and inductance 5 are all mounted on a suitable metallic plate I6 and insulated therefrom by means of the porcelain insulators Il. The mounting I6, as well as the box herein designated I 8, surrounding the main portion of the circuit for shielding purposes, should comprise a pure metal of low electrical resistivity, such as aluminum or copper. In one successful embodiment an aluminum was employed for the box I8 and the mounting I6, mainly because of its light weight.

Referring to the lower portion of Fig. 1, it shouldbe noted that condensers II) and I I actually comprise two adjustable phosphor bronze springs II) and II oppositely disposed with respect to a central metallic plate I9 which is directly connected to the cathode of the electron discharge devicel, which in this case comprises an Acorn tube of the type known in the art as RCA 955, or an A-20l4, or any other electron discharge device suitable for operation at these frequencies. A pair of threaded brass screws 20 and 2|, each with an insulated extension 22, and operable by means of knurled thumb nuts, are employed for adjusting the capacitance of the condensers l0 and II by means of varying the distances between the springs I0 and II and the central plate [9.

When the upper part of the construction, consisting of the antenna and the tuned circuits 4, 5, is properly located in position for use with the aid of screws, not shown, securing the upper and lower portions of Fig. 1 together, inductance coil 5 will be located adjacent to coil 6 for magnetic coupling thereto when the circuit is used as a transmitter. Coil 6, it should be noted, also consists of one and one-half turns of suitable size wire. When the circuit is used as a receiver, coil 5 may be shifted slightly to be adjacent coil l2 forelectromagnetic coupling to this last coil. Coil l2 in practice may comprise a single turn wire of suitable size.

In one successful specific embodiment tried out in practice, the elements of the invention had the following values:

Condenser- 8.00005 mfd.

Grid leak 9- 30,000 ohms.

Choke coil I 3fifteen turns of #24 wire on a form one and one-half inches long and one-quarter inch in diameter.

Coil l 2- one turn of #18 wire.

Coils 5 and 6- each approximately one and onehalf turns of #18 wire, onequarter inch in diameter.

RCA #955 Acorn tube, or A-2014 Acorn tube.

A factor of major importance in the construction of an arrangement in accordance with the invention is the fact that the leads connecting the various elements together are reduced to an absolute minimum, since extremely short leads are absolutely necessary in using such a circuit at the extremely high frequencies of the order of 300 megacycles or above.

In the present invention there are no leads whatsoever between the grid and anode terminals located externally of the envelope of the tube and the terminals of the condenser plates Hi and I i, inasmuch as these terminals are designed to be in actual physical contact with one another and are so connected. Similarly with respect to the coils 6 and I2. It will be observed that one terminal of each of these anode and grid inductances is in actual physical contact with a terminal of the condensers l0 and H, and if so desired, instead of separate terminals for the condensers for both the coils and the tube electrodes, the same terminals on the condensers may be used for the inductance coils as are used for the electrodes of the vacuum tube.

What is claimed is:

1. In a portable ultra high frequency system, an electron discharge device oscillator having an anode, a cathode and a grid, a condenser comprising a central planar metallic element and two metal plates mounted on both'sides of said central element, said oscillator and condenser being located within a metallic box, means comprising insulating rods supported from opposite sides of said box for adjusting the position of said plates with respect to said central element, a connection from said central element to said cathode, connections from said plates to said grid and anode,

and an antenna circuit located externally of and mounted on said box and coupled to the electrodes of said device.

2. A compact high frequency communication apparatus comprising first and second removable portions adapted to be attached together, an antenna, a tuned circuit, and a condenser serially coupling said antenna and tuned circuit, all

mounted on said first portion, an electron discharge device including inductance coils and condensers connecting the electrodes thereof together for enabling the generation of oscillations all mounted on said second portion, said tuned circuit of said first portion being so constructed as to be adjacent and magnetically coupled to one of said inductance coils of said second portion when both portions are attached together.

3. In a high frequency system, an electron discharge device oscillator having an anode, a cathode and a grid, a condenser comprising a central planar metallic element and two metal plates mounted on both sides of said central element, said electron discharge device and condenser being located within a metallic shielding box, means for adjusting the position of each of said plates with respect to said central element, a connection from said central element to said cathode, and connections from said plates to said grid and anode, said means comprising two adjustable insulating rods supported from opposite sides of said box and contacting said plates.

4. A system in accordance with claim 3, characterized in this that said antenna consists of a dipole having two arms each of which is mounted externally of said first portion and on one side of a metal plate, said tuned circuit being located on the other side of said metal plate and including a condenser whose terminals are coupled to said antenna through, but insulated from, said plate, and means on the same side of said plate as the antenna, extending through said plate, for adjusting the capacitance of said last condenser.

5. A compact high frequency communication apparatus comprising a metallic shielding container including first and second removable portions adapted to be attached together, an antenna and a tuned circuit mounted on said first portion, an electron discharge device oscillator including a grid inductance coil and an anode inductance coil mounted on and Within said second portion, said tuned circuit of said first portion being so constructed and arranged as to be adjacent and magnetically coupled to one of said inductance coils of said second portion when both portions are attached together.

6. A compact high frequency communication apparatus comprising a metallic shielding container including first and second removable portions adapted to be attached together, an antenna and a tuned circuit mounted on said first portion, an electron discharge device oscillator including a grid inductance coil and an anode inductance coil mounted on and within said second portion, said tuned circuit and antenna being so constructed and arranged that the antenna is located externally of said container and said tuned circuit adjacent and magnetically coupled to said anode inductance coil when both portions are attached together.

ROBERT M. MORRIS.

CAREY P, SWEENY.

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