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An Explanation of a Proposed Scheme for Tuning a Stationary Receiver from Anywhere in the House.

A Remote Radio Control Without Wires
Radio News, February 1928

The loops in the station selector (on the small table) are concealed with in box; the left-hand cabinet on the table contains the band amplifiers; and the fixed-frequency receiver is on the right.

Believe it or not, the average radio listener is a lazy mortal. This may seem to many to be rather a harsh statement, but it is true nevertheless; else why should we find described daily new devices to eliminate some of the heroic labors that the listener must perform in order to operate his set? We now have trickle chargers that can be left connected to the storage battery, so that the owner will not have to carry the battery down to the cellar to charge it, or exert himself unnecessarily by lifting the telephone receiver from the hook and asking a service man to come around and get the battery.

The latest labor-saving device to appear is one that has great possibilities. No longer will it be necessary for Father to leave his comfortable arm-chair to tune in on a different station, because Mother doesn't like the color of the announcer's necktie at Station WXYZ; no, "them days is gone forever," if you have one of these "remote controls." All that need be done is to turn a knob on the front of a little box, which stands on your chair arm, and tune in the station that Mother wants to hear. No need to get out of that very comfortable position with your feet on the mantle-shelf to adjust the volume to its proper intensity; merely turn another knob on the same small box and the deed is done. Simplicity itself, isn't it?

A feature that will make its appeal to the female members of the family is that the only apparatus which need be in sight is the small control box and the loud speaker. No longer will these words be necessary in the family bosom of the experimenter: "When are you going to get a decent cabinet for that radio? I'm ashamed to have that old piece of junk sitting there on the living room table." (No matter how splendidly the sat may work, it is always known as "junk" to the females of the family.) For with the remote-control system that does not utilize any wires from the control apparatus to the set (which is the case in the method, invented by Bowden Washington and Wilson Aull, Jr., of New York City) the band amplifier and the fixed-frequency receiver may be stowed in a closet with all the batteries, chargers and what not.

Theory and Operation

Signals from all stations within the receiver's range are amplified in the band amplifier, and the one to which it is desired to listen to is tuned in by the station selector and transmitted on a new wavelegnth to the fixed-frequence receiver.

The question now arises, how is this done? To tell the truth, the process is simplicity itself. Refer to Fig. 1, in which will be found diagramed a band amplifier, a portable control box and a fixed-frequency receiver, together with four loop antennas marked A, B, C and D. On the control box are indicated two controls; a station selector and a volume adjustment. The band amplifier, to which is connected the regular ariel and ground, is a radio frequency amplifier which builds up the signals of the waveband from 200 to 550 meters. It may use fixed R.F. transformers with overlapping tuning curves. Thew output of the amplifier is connected to a loop antenna, which, as shown in Fig. 1, radiates all the signals picked up by the outside aerial.

The radiations from loop A are picked up by loop B, on the input side of the portable control box. Across this loop is connected a simple regenerative detector, the output of which modulates an oscillatory circuit, operating on a frequency that is either above or below the broadcast waveband. Let us assume this frequency is about 540 kilocycles. Then from loop C we have a wave of 540 kc. frequency modulated by the detected signal from a certain station, let us say WJZ, which is selected by the regenerative detector. The modulated wave from loop C is picked up by loop D, across the input of the fixed-frequency receiver, this frequency being the same as that of the oscillating circuit in the control box, 540 kilocycles. Thus only the single frequency, 540 kc., will in any way affect the receiver, as it is tuned to that frequency alone.

Control Box is Simple

The small box that is placed on Father's chair arm is very simple of construction. It is entirely self-contained; i.e., the loop antennas, the necessary batteries for the two tubes, the apparatus for tuning and the oscillating circuit are all within the confines of the small box. In order to facilitate construction, tubes of the 299 type are employed so that dry-cell batteries may be used and, consequently, two of the small 22-1/2-volt "B" batteries can be stowed away in a convenient corner. It is designed for sufficient sensitivity with non- adjustable automatic regeneration, so that only two controls are necessary--the grid tuning condenser for selection and a volume control, which may be a potentiometer controlling the modulation of the oscillator.

This control box may be as decorative as may be desired and the two controls, appearing on the outside of the box, can be made to correspond to the scheme of the decoration, just as in some of the receivers appearing on the market at the present time.

The band amplifier and the receiving set can be made to operate from the same batteries or socket-power devices, which can be hidden in a closet along with the rest of the apparatus, except the portable control and the loud speaker. The latter can be arranged so that when it is plugged into a jack, it will turn on the filament current to the tubes, which will be cut off when the speaker plug is withdrawn. This may be easily done with a filament-control jack. Any number of these jacks may be distributed about the house, wired in parallel; so that, no matter it what room it is desired to have music, the loud speaker and the control box are all that is necessary to carry there. There is little doubt that the radiations from the control box will be strong enough to operate the receiver from any point in an ordinary-sized house. If the area to be covered is greater than that of the average eight-room house, then more powerful tubes can be used in the control box which, of course, then would have to be enlarged to accommodate the different batteries.

The band amplifier should have at least three stages, so the entire waveband will be satisfactorily covered and amplified sufficiently. The transformer in the first stage can be made to cover the frequencies between 200 and 350 meters; that in the second, those between 325 and 450 meters, and the last stage, between 425 and 550. In this way, no matter where the signal lies in the broadcast band, it is amplified and retransmitted to the control box.

The single-frequency receiver, which we have assumed to be operating on 540 kilocycles, can be any standard broadcast receiver. Most of the sets that are being built at the present time tune sightly above and below the broadcast waveband. It is only necessary to tune the set once to the frequency at which the oscillator is working and allow the controls to rest in those positions. In reality, no matter how many controls the set has, they are reduced to one by employing the control box.

[For contrast, see the 1939 Kadette Tunemaster "remote control for any radio"--Ed]


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