US2281709A - Beat oscillator - Google Patents

Description

May 5, 1942.

wzm

E. OLSON 2,281,709

BEAT OSCILLATOR "Filed Feb. 17, 1941 [g 7 V IIIII I I INVENTOR. ELMEE' [15cm Patented May 5, 1942 UNITED STATES PATENT OFFICE BEAT OSCILLATOR Elmer Olson, Pomeroy, Iowa Application February 17, 1941, Serial No. 379,219

1 Claim.

The principal object of this invention is to provide a tuned grid beat oscillator for accurately calibrating radio sets or other tuned electrical apparatuses.

A further object of this invention is to provide a beat oscillator circuit which will radiate a tuned frequency beat on any pre-selected frequency for setting or locating station frequencies and for adjusting trimmer condensers, push button tuning controls or the like of a radio set.

A still further object of this invention is to provide an oscillator of the tuned grid 'type which can be set at a desired frequency and which will, when a radio set is tuned to the principal harmonic of the frequency, give a visual signal to indicate the resonance of the respective circuits relative to each other.

A still further object of this invention is to provide a beat oscillator circuit which is extremely economical in manufacture, durable and efiicient in use.

These and other objects will be apparent to those skilled in the art.

My invention consists in the construction, arrangement and combination of the various parts of the device, whereby the objects contemplated are attained as hereinafter more fully set forth, pointed out in my claim and illustrated in the accompanying drawing, in which:

The figure is a diagrammatic view of the circuit employed in my beat oscillator or frequency meter.

It has heretofore been difficult to set the push buttons of a radio unless the actual broadcasting station to be selected is tuned in, and even then it is difficult to hit the period of resonance of the carrier wave that is in exact tune with the station. Some attempts have been made to do this by the use of an ordinary wave meter, but this is difficult due to the broadness of the carrier of such mechanisms and the fact that the wave meter must have its antenna pick-up changed for each frequency variation. Furthermore, such frequency beat meters relied upon an audible signal rather than a visual indicator, were extremely critical as to their own inherent adjustment. I have overcome such disadvantages as will be appreciated and as will be hereinafter more fully set forth.

I have used the numeral l to indicate an ordinary triode type of vacuum tube having the ordinary plate element ll, grid l2 and filament [3. One side of the filament element is connected to the center tap of a battery or like M,

outer lead wires of the battery M. Imposed in this last mentioned lead line is a switch l5 and rheostat It. The other end of the battery I4 is connected through the medium of an electric lead line ll with one side of a milliammeter Ill. The numeral l9 indicates the primary windings of a coil having one end in electrical communication With the plate II and its other end in communication through a lead line 20 with the other side of the milliammeter H3. The numeral 2| indicates a condenser placed in multiple or shunted across the two terminals of the milliammeter lt. The secondary winding of the coil I have designated by the numeral 22, which is shunted by a variable condenser 23 as shown in the drawing. The upper end of this coil 22 is connected to one side of a condenser unit 24 and the other side of the condenser 24 is connected, through the medium of an electric lead line 25, with the grid l2 of the tube Ill. The lower end of the coil 22 is connected to the central tap of the battery I. The antenna plate 26 is connected into the circuit including the grid 12, variable condenser 23, and coil 22 as appears clearly in the drawing. The numeral 21 indicates an electric lead line having one of its ends in electrical communication with the lead line 25 and its other end designed to be secured to the control grid of a radio or like.

The practical operation of my device is as follows:

The complete unit is placed at a distance from the radio set to be tuned and the filament switch I5 is closed, thereby activating the filament l3 of the vacuum tube ill. The variable condenser is tuned to the frequency desired and calibrated for that frequency. This causes the vacuum tube I0 to oscillate at a certain frequency, thereby registering a definite beat on the milliammeter I8. The radio set is then tuned until the highest frequency of beat is indicated by the milliammeter, at which time the radio receiving set will be in resonance with the frequency determined on the condenser unit 23. Inasmuch as all of the various frequencies can be calibrated on the control shaft or dial of the condenser 23, it is merely necessary to set this condenser at any desired frequency such as one thousand kilocycles, twelve hundred kilocycles or the like, and then tune the radio receiving apparatuses until the highest frequency of beat is noted on the milliammeter IS. The set can then be adjusted and will be accurately in tune for the frequency so determined. In some instances, it is necessary and the other side is connected to one of the to connect the wire 21 to a control grid of the controls thereon.

radio set in order to intensify the reading of the milliammeter and the frequency of its beat. Thus it is possible to trace the operation of the radio set over its entire frequency band to determine the correct calibration point on the radio set for pre-setting automatic push buttons or other Thus it will be seen that I have provided a beat oscillator for use in tuning radio receiving apparatuses which fulfills all of my objects and presents many more obvious advantages. Its extreme simplicity of operation makes it a highly desirable instrument for use in setting automatic push button controls on across said secondary of said tuning grid, a milmodern radio apparatuses, and the equipment can be made in a small compact form and gives a visual signal indicating the period of resonance of the receiver relative to the frequency set'on my device.

Some changes may be made in the construction and arrangement of my improved beat oscillator without departing from the real spirit and. purliammeter having one of its terminals in communication with a source of electrical energy and its other side in communication with the primary winding of said tuning grid, and an electric lead line in communication with the other'side of said primary coil and the plate of said tube.

' ELMER OLSON.

Images