## An oscillator frequency control circuit

How the Discriminator-Detector Circuit Works. The discriminator-detector network as the name implies, discriminates between applied intermediate frequencies which are too low and thpse which are too high, and produces a corresponding direct current or voltage whose polarity depends upon the direction of frequency departure from a prescribed intermediate frequency. This d.c. voltage is applied to a control element which in turn causes a shift in frequency of the local oscillator such as to bring...

## The Cathode Ray Oscillograph

The cathode ray oscillograph is at present one of the most useful of radio testing devices. Although as yet relatively expensive, its applications are so numerous that it will readily replace a number of measuring instruments of more or less satisfactory characteristics. A few of the more important applications of the instrument are the study of wave shapes and transients, measurements of modulation and peak voltages, adjustment of radio receivers, comparison of frequencies, the indication of...

## Galvanometer is used r the radius of the coil in centimeter

6, the angle of the needle deflection in degrees and I, the current in c.g.s. units. FIG. 1 The tangent galvanometer consists essentially of a short magnetic needle suspended at the center of a coil of large diameter and small cross-section. In practice the diameter of the coil is approximately 17 times the length of the needle. If the instrument be so placed, that when there is no current in the coil, the suspended magnet lies in the plane of the coil, that is, if the plane of the coil be set...

It is undoubtedly true that without the aid of radio, aerial navigation would not have advanced to the stage where giant airliners arrive and depart keeping time schedules unheard of only a few years ago. As a matter of fact the airplane is rapidly closing in on such proven means of transport as trains, ships and buses in regards to exact time schedules in all sorts of weather. It is a recognized fact that the actual value of aircraft radio installations depends entirely upon radio facilities...

## The instrument is illustrated in fig and its connection diagram in fig

It has a 20,000 ohms per volt sensitivity on five d.c. voltage ranges. A.c. readings are made on single arc scale. The ranges for dx. current measurements are 0- 0.1 10 50 -250 m.a. la lOa. Ax. or dx. voltage measurements have the following ranges 0-2.5 10 50 250 1,000 v. Five decibel ranges provide power level measurement from 14 to 54 db. Resistances are measured on the following scales 0-3,000 -30,000 3 Meg. 30 Megohms. The instrument is equipped with pin jacks for mounting model 666 socket...

## Through the choke coil and the internal plate circuit

Condenser C prevents this d.c. current flowing through coil L, when S is closed, thus preventing discharge of the B battery through coil L, and also making the reactances of the circuit LC to radio frequency current low. When S is closed a surge in current takes place via condenser C and coil L, which is absorbed from the internal plate circuit. Since the choke maintains the battery current steady, the variable current through coil L induces a voltage in coil L'. Assuming the induced voltage is...

## Phototube Relays

Since as already described the current change accomplished in photoelectric cells is very small, it is necessary to employ an amplifier in order to receive a current of sufficient strength to operate a relay. When selecting a relay for operation in a photoelectric circuit, it is of course necessary to be informed about the characteristics of the circuit, speed of operation, etc. It is also important that the relay employed is able to carry the load to be operated across its contacts without...

## Thereby forming what is known as a ring type shunt the

Total ring resistance value being 375 ohms. The resistance values of the 75 ohm shunt resistors are determined by multiplying the total ring resistance by the full scale current of the meter, dividing the result by each range value, in turn, from the common terminal, and subtracting the sum of the preceding values from each newly-determined value. When the ring value of 375 ohms is multiplied by the full scale sensitivity value of 0.001 ampere, 0.375 is the result, into which each range value...

## Used than the reverse circuit which is frequently used when the

Voltage supplied to photocell equipment and the light source is unstable or variable. Fig. 5. Typical A. C. operated amplifier. Forward circuit for phototube operation. Fig. 5. Typical A. C. operated amplifier. Forward circuit for phototube operation. Fig. 6. Typical A. C. operated amplifier. Reverse circuit for phototube operation. Similarly a forward and reverse circuit may also be operated from an alternating current amplifier. See figs. 5 and 6. The Function of Grid Resistors in Amplifier...

The Federal Communications Commission, by virtue of authority granted to it by the Communications Act of 1934, has promulgated various specifications and regulations applicable to ship-board radio installations. Most of these regulations are found in its General Orders and its rules and regulations. FIG. 1 Photographic view of S.S. Manhattan. View of radio room and equipment shown in fig. 2. FIG. 1 Photographic view of S.S. Manhattan. View of radio room and equipment shown in fig. 2. The...

## Commonly used

However, on very long wavelengths it has been found advantageous to use step-up ratio transformers, by having a greater number of secondary than primary turns. -iliW'I'I'I'H b-battery FIG. 14 Three stage radio frequency amplifier circuit. -iliW'I'I'I'H b-battery FIG. 14 Three stage radio frequency amplifier circuit. In the transformer coupled circuit shown in fig. 14, the filaments are connected in parallel across the common A battery with a variable rheostat to adjust the filament current. A B...

## Using Ohms law EIR X

Or 1,000 250 0.001X fromwhichX -QQQ 750,000 ohms. The resistor to be inserted should have a value of 750,000 ohms and each reading taken after insertion of this new resistance should be multiplied by 4 to obtain the true voltage. A Combination Volt-Ammeter. Since the construction of a voltmeter and ammeter is the same, the difference being that in an ammeter resistors are placed parallel to the moving coil, while in the voltmeter resistors are placed in series with the moving coil, it is...

' x p' -1 nifr i rectifierj ' x p' -1 nifr i rectifierj lt k 84 Fig. 8. Circuit diagram of a 7-tube automobile radio receiver, Philco Lincoln-Zephyr L-1424. This receiver is equipped ' with an electro-dynamic speaker, which is mounted on the rear of the instrument board extension. The volume control is automatic, a specially designed input circuit to match thetire compartment door antenna, and an elaborate filter network to reduce ignition noise disturbance is included. The receiver is designed...

## Ft these values may be substituted for Pi and P in equation

The logarithm of a number is the power to which 10 must be raised to equal the number in question. For example, log. 100 2 because 10 100. Similarly log. 867 2.9380 because 102'3380 867, etc. Example. What gain in decibels will be received if the voltage of an amplifier rises to 5 times the normal level at a certain frequency N 20 log.io 5 20X0.699 14 decibels Approx. Reference Level. It is important to note that the decibel is not a power unit such as the watt or kilowatt but is strictly...

## At both audio and intermediate frequencies but filters must also

Be inserted to separate the frequencies so as to prevent feedback. A typical reflex circuit using one tube and a crystal detector is shown in fig. 28. Intermediate Frequency Amplifiers. The function of the intermediate frequency amplifier in a super-heterodyne receiver is to convert the r.f. signal to an intermediate frequency. To obtain this change in frequency, a frequency-converting device consisting of an oscillator and a frequency mixer is commonly employed. In a circuit of this type two...

## Phototube Amplifiers

Since the current generated in most photocells is very low and is usually measured in microamperes, it is evident that for practical operation a way must be found to increase this feeble current, for practical relay operation. Therefore in order to increase the power output of the photocell a method of amplification very similar to that associated with radio circuits is employed. The amplifier tubes may be of the high vacuum or of the gaseous type. .When the...

## Sensitivity

The three groups are inter-dependent with selectivity th lt most important factor. FIGS. 1 and 2 Block diagrams showing essential units of a regenerative and a tuned radio frequency regenerative circuit respectively. FIGS. 3 and 4 Block diagrams showing essential units of a super-regenerative and a super-infra regenerative circuit respectively. By definition,' selectivity of a receiver is its ability to discriminate between signals of various frequencies. The sensitivity of a receiver is the...

Schematic wiring diagram of a 4-tube Handy-phone for inter-office communication. Model FM-41 General Electric. The handy phone is an efficient loudspeaker phone system for use in offices, homes, hospitals or other places where voice,communication between a central station and one of more remote stations is desirable. The system comprises one Model FM-41 master station and from one,to four Moddl FS-5 remote speaker phone stations. The master station employs four General Electric tubes in...

## Principle of Operation

The radio compass is an imti ument for observing by means of radio, the direction of a station emitting radio signals briefly, in aerial and marine navigation, it is an instrument for taking radio bearings. Operating Principles. Since the radio compass is built around the loop antenna it is necessary to understand its principles of operation before undertaking a study of the other units. The radio compass utilizes the directional receiving properties of the coil, which consists essentially of...

## Response in the Infra Red or Heat Wave Region The

Range of sensitivity of various photo-electric devices extends from 2,000 Angstrom in the ultra-violet region to approximately 20,000 Angstrom in the infra-red or heat wave region. In practice, one need not expect any useful response beyond 12,000 Angstroms in cesium-oxide phototubes. It seems doubtful at present if more than a mere trace of photo-electric effect will ever be experimentally realized for the infra-red region beyond, say, 30,000 Angstroms. Quite possibly dependence will have to...

By definition a public address system consists of a sound amplifier system supplying sound programs from radio, phonograph or microphones to one or more loud speakers. - VOLUME CONTROL REPRODUCER PICK-UP AMPLIFYING-RADIO RECEIVER AND CONTROL PANEL FIG. 1 Schematic view of a music reproducing and program distributing system. A public address system may be designed to amplify sound in one single place such as in an auditorium or in a number of rooms such as in hotels or hospitals. In order that...

## Paper upon which theexactoutlineof the panel or chassis has been

The parts are generally moved around until a satisfactory arrangement has been obtained. The centers and sizeof the various holes are then laid out on the paper, after which the SCRATCH ON METAL TO FACILITATE BENDING One Side Only FIG. 2 After corners has been removed and the drilling and cutting completed, the projecting sides of the metal is bent down 90 to form the chassis as shown in fig. 4. paper is transferred to the panel and properly fastened by gummed paper or adhesive tape. Only...

There may be confusion in the minds of some as to batteries so a classification of types and functions will be helpful, particularly to the novice. Radio batteries may be classified according to the three elements of the vacuum tube which they serve, as A battery B battery C battery The three elements of the common vacuum tube, filament, plate and'grid are often designated by the letters A,.B and C. The order in which the letters are assigned corresponds to the historical development of the...

## Quarter more current into the battery than is taken out

If the lamp burn brighter than usual, turn the battery around. From 32 volt farm lighting plants only one 24 volt B battery can be charged from one lamp. 48 volt B batteries must be charged half (12 cells) at a time. Use either a 10 watt or a 20 watt 32 volt lamp. A 10 watt lamp charges at .1 ampere -20 watt lamp charges at .2 ampere. From 110 volt power lines, one, two or three 34 volt batteries can be charged from one lamp by connecting them in series...

## Physics of Sound

When air is set in vibration by any means, sound is produced provided that the frequency of vibration is such that it is audible. If a violin string in tension be plucked, as in fig. 1, it springs back into position, but due to its weight and speed, it goes beyond its normal position, oscillates back and forth through its normal position, and gradually comes to rest. These vibrations produce sound. As the string moves forward it pushes air before it and compresses it, also...

## How the Wave Length of an Aerial May Be IncreasedIt

Has been found convenient to include an inductance in the down lead wire to the receiver for the purpose of passing the received signal voltage to the set. Sometimes this added inductance coil is connected directly to the set and at other times it is coupled magnetically to the tuned circuit. When in the closed circuit type, a coil of inductance L micro-henries is connected in the down-lead of an aerial whose inductance is La micro-henries, the new wave-length is being given by . X 1,885V L La...

## Procedure of making this test

Ened to cardboards and insulated from contact with car body. ened to cardboards and insulated from contact with car body. FIG. 2 Illustrating location of roof type antenna. FIG. 2 Illustrating location of roof type antenna. x If it be found that the top support screen is grounded or if no screen be present, it will be necessary to remove the entire head-lining as shown in fig. 2. In the former case the screen may be insulated by removal of a strip several inches from all edges, as well as from...

FIG. 1 Diagrammatic representation illustrating similarity between wire and radio telephone. It is thus possible for the personnel of the above to communicate with their offices or homes when within range of a coastal harbor radio telephone station. At present radio telephone service is available to boats in the areas served by the shore stations at Boston, New York, Miami, Seattle, San Francisco, Los Angeles and Norfolk. In this connection it may be mentioned, that the regulation of the...

It is now generally recognized that successful radio receiver trouble-shooting or radio servicing requires an intimate knowledge of thousands of component parts constituting the receiver. Years ago, when the best receiver consisted of a condenser, a coil and the catwhisker thrown together in haphazard manner, anybody in possession of a buzzer, a pliers and a screw-driver, could find and eliminate the trouble in short order. However, since then, radio receivers have gone through an epoch of...

An automatic alarm is a device used to enable a ship in distress to summon aid at any time by radio from a nearby vessel, and especially during those periods when the radio operator on the nearby vessel might not be on watch. Special regulations governing this distress signal and the number of operators which their installation shall release are now in force. 0 5 10 15 20 25 30 35 40 45 50 55 . 60 SECONDS 1 i m 1 I i i i i I 1 i i i I 11 ii I i m i ii i i 1 m i 1 i 1 ii 1 i ii 1 i t i i I i i i...

## Commercial Type Analyzers

The external view of this instalment is shown in fig. 4. and its internal connection diagram in fig. 5. The instrument is principally a volt-ohm-milliammeter for All voltage ranges are available at the pm jacks, and by means of socket selector units may be had through the plug. They are 0-1 2.5 5 10 25 100 250 500 1,000 volts, eithef a.c. or d.c. The individual ranges are selected by means of the large selector switch. A reading cannot be had till either the...

## Transformers

The alternating current transformer represents an example of the practical utilization of mutual inductance. By definition a transformer is a form of stationary induction apparatus in which the primary and secondary coils or windings are ordinarily insulated from one another, their relative position being fixed. In the case of low frequency and power transformers, the primary and secondary windings are wound on a common iron FIG. 1 A transformer in its simplest form consists of two separate and...

## The Crystal Variously Called PiezoEIectric Pickup The

Action of this device, which on account of certain favorable qualities has found an increased use, depends upon the property of a Rochelle salt crystal in converting mechanical motion into electrical voltage. In practice this is accomplished by placing two small crystal slabs together which results in what is known as a bi-morph crystal element. This crystal element is then mounted between two small discs of sponge rubber in a bakelite housing, and a light aluminum rocker arm with rubber...

## Cannot be made in the inner jacks since the circuit is opened

Grid and screen current measurements are made in the same manner as the plate current. All current ranges are available for this purpose. The push button marked Press for D.C. must be held down for this test. These readings are obtained by placing one end of each of a pair of leads in the M.A. pin jacks and the other ends in the two pin jacks opposite the terminal of the grid desired. The plate current of the second plate of rectifier tubes is tested as above. It is advisable to...

## The decibel ranges provides measurements of power levels between to db

n r ----1 iWftiiiAM MndJ 779 nnnlvzpr. n r ----1 iWftiiiAM MndJ 779 nnnlvzpr. Weston Model 772 Analyzer. This analyzer is designed to make the necessary tests on present day equipment such as commercial radio receivers, transmitters, television receivers, FIG. 14 Wiring diagram of Weston Model 772 analyzer. FIG. 14 Wiring diagram of Weston Model 772 analyzer. public address systems, vacuum tube and cathode ray equipment, etc.

## Automatic Frequency Control A F C

In the early kinds of radio sets the receiver control had to be operated manually by the turning of one or more volume control knobs. In modern receivers however, automatic frequency control has been incorporated to make this constant manipulation of the volume control knobs unnecessary. The action of the automatic frequency control circuits in superheterodyne receivers is such that any mis-tuning by the listener or any frequency drift in the set after it has been properly tuned is...

## Vacuum Tubes

A vacuum radio tube in its simplest form is somewhat similar to an electric light bulb, but contains a number of metallic elements for various purposes for use in conjunction with radio transmission and reception. The parts of a typical vacuum tube is shown below. Fig. 1. Parts and assembly of a typical glass radio tube. The filament, grid screen and plate are sealed in the tube, from which the air has been removed. Courtesy R.C.A. Mfg. Co. ' Fig. 1. Parts and assembly of a...

## Taper reamer in for brace

1 Taper reamer in. for brace. 1 Center punch. 1 Electric soldering iron 100 watts, small pointed tip . 1 Heavy knife 1 Circle cutter adjustable for brace. 1 Screw driver bit for brace. 1 Countersink for brace. 1 Carpenter's ratchet brace. . 1 1 Hand drill 2 speed . 1 Yardstick or other straight edge. x 1 Carpenter's plane 8 to 12 in. . 1 Combination square 12 in. . 1 Pr. wing dividers 8 in. . 1 Long shank screw driver with screw holding clip i i' n. , blade . 1 Screw driver 6 in. to 7 in. M in....

## The actuating wire has a tendency to expand when not in

Use, hence it is necessary to set the pointer back to zero before sending a current through it. 5. They are uneconomical, i.e. the current consumption is considerably in excess of that in other types. FIG. 16 Simplified diagram illustrating the construction of a hot wire instrument. AT, represents a silk thread connected to spring S, wound around pully P, and attached to a bead threaded on wire AB. Wire AB, made of platinum alloy, is connected in the circuit whose current is to be measured....

## For further treatment of transformers see transformer chapter

FIG. 4 Illustrates connection and rectifier tube to obtain half-wave rectification. FIG. 4 Illustrates connection and rectifier tube to obtain half-wave rectification. FIG. 5 Illustrates connection and rectifier tube to obtain full-wave rectification. FIG. 5 Illustrates connection and rectifier tube to obtain full-wave rectification. Method of Line Voltage Regulation. In certain locations where comparatively large fluctuation in voltage is experienced, due to variation in the load requirements,...

Radio telephony may be defined as the transmission to a distance of speech, music and other sounds through space without wire, by means of electro-magnetic waves. In the standard system of radio telephony continuous waves are used of much higher frequency than those of audible sounds. The amplitude of those waves is modulated by the connection of a microphone in the transmitting circuit. Receiving apparatus are similar to those employed in radio telegraphy and are designed so that the head set...

## Wireless Control System

By utilizing a device recently developed by the Philco Radio & Television Corp., it is possible to operate a radio receiver by means of remote control. The control box popularly known as the Mystery Control is portable, and the desired station may be dialed in a manner similar to that of a dial-type telephone, except that no connected wires are necessary. .With reference to fig. 11, showing the control box, the tube and coils form an oscillator which can be...

## The permanent magnet

A speaker of this type illustrated in figs. 4 and 5 consists principally of the following parts 1, field coil 2, voice coil 3, cone. FIG. 4 Cross-section view of a dynamic type loud speaker with a moving coil driving a cone type diaphragm. Details of the various units are here clearly represented. FIG. 4 Cross-section view of a dynamic type loud speaker with a moving coil driving a cone type diaphragm. Details of the various units are here clearly represented. The field coil...

## Dynamic speaker previously described

FIG. 6 When the dynamic speakers as in some commercial sets are connected by means of plug and cable to the chassis, the connections may be as shown in fig. 6 or 7 generally however, there is no set rule for these connections. The output transformer may be mounted on the receiver chassis' or on the speaker frame. Again, the output tubes may be connected in parallel or in push-pull. Therefore, the connections shown are'typical only and may not be considered as standard, but in each case the...

## Phonograph Pickups

By definition a phonograph pick-up is a device which converts the vibrations of a phonograph needle in traversing a phonograph record into audio frequency currents for reproduction through a radio receiver. See fig. 1. motor leads PIG. 1 Modern phonograph pick-up unit. motor leads PIG. 1 Modern phonograph pick-up unit. Phonograph pick-up operating on various well known principles have been developed, such as the condenser type, carbon resistance, magnetic or crystal type. The pick-ups at...

## Each radio beacon a definite signal

The common method of ascertaining the location of a ship equipped with radio compass is by means of cross bearings using two or more radio beams as shown in fig. 1 or by visual and radio bearings in combination. Of course the usual principles apply, as to employing stations which will give good intersections, and as to allowing for the compass aboard ship and shore radio beacons. compass aboard ship and shore radio beacons. distance run between the times of taking bearings if...

## With its resistance built up to a value of ohms requires a

Potential of 0.3 volt (300 millivolts) to cause a full scale current of 1.0 milliampere to pass through the meter. FIG. 19 Front view arrangement of Supreme Model 339 radio set analyzer. FIG. 19 Front view arrangement of Supreme Model 339 radio set analyzer. The shunt resistor for the 5 milliampere range, being in parallel with the meter, will have the same 0.3 volt potential difference. Since 1.0 milliampere of the 5 milliampere range ' will pass through the meter, the shunt resistor will pass...