CHAPTER 23
NAVY RECEIVERS
INTRODUCTION

Navy receivers are precision instruments, designed to bring in messages under the most adverse conditions. They are highly selective and sensitive, but careless, improper tuning can cause the set to lose half or more of its efficiency. Therefore, it is necessary for you to learn properly and practice diligently the tuning procedures. After a short time the operation of receivers such as the RBB or RBC will become nearly automatic.

The Navy receivers discussed in this chapter are not the only types you will find on ships and shore stations, but they are the sets you will find most frequently. Some of the models will be used daily and others only occasionally for special purposes. Regardless of how much or how often, you must learn how to tune all models on your ship or station. You can expect to be called upon to operate any set in an emergency.

The instructions in this chapter have been taken from the manufacturers' instruction books. They are

You can expect to find variations in the techniques of tuning. Step 3 may become step 1, and step 5 omitted entirely, but whatever the method or system used, be sure you are getting the most out of your receiver.

The use of special controls designed to eliminate the interference of noise and static is of considerable importance. A good operator, by intelligent use of these CONTROLS, can bring in a message clearly where a careless and inefficient operator will have his signal completely masked in noise.

THE MODEL RAK/RAL RECEIVERS

The models RAK/RAL are companion receivers, usually installed in pairs. They are designed to cover two

Both receivers are TRF, using two stages of tuned r.f. amplification and a regenerative detector, followed by two stages of audio amplification. Both have an output limiter circuit.

The sets are designed for C.W. reception, but can be used on I.C.W. or MOD.-C.W. The high selectivity, and the low-pass filter in the audio section of the RAL, results in considerable distortion of VOICE reception.

The production of the BEAT NOTE for C.W. reception is obtained by incorporating an AUTODYNE oscillator in the regenerative detector circuit. Since this type of oscillator requires frequent adjustment, a REGENERATION CONTROL is mounted on the operating panel. For C.W. reception, the REGENERATION control is adjusted to produce

The RAL receiver has a FREQUENCY VERNIER connected into the autodyne circuit that permits variations in the pitch of the audio beat note. This control is not a part of the RAK equipment.

A LOW-PASS FILTER is included in both the RAK and RAL circuits. This filter has three controls: OFF-ON, a RANGE SWITCH, and a 10 point AUDIO TUNING dial. The RANGE SWITCH selects one of two frequency bands, 450-770 or 770-1300 cycles. The TUNING DIAL selects the desired frequency within these ranges.

The original RAK and RAL receivers were designed for d.c. operation. All subsequent modifications are designed for 110/120 volt, 60 cycle, single-phase, a.c., but have provisions for emergency d.c. operation.

Modifications 1 through 5 are substantially the same receiver. Modifications 6, 7, and 8 have increased protective shielding to prevent high frequency radar interference.

It is recommended that each RAK and RAL have a separate antenna, but when it is necessary to operate both from a common antenna, a loose input coupling must be used.

INSTRUCTIONS FOR OPERATION OF THE RAK-RAL RECEIVERS

TUNING FOR C.W. SIGNALS

1. Turn on the power to the set you desire to operate. If you wish to use both, turn on both sets. remember, if the installation is a double RAK/RAL unit, the switches are on the CONTROL UNIT. If a single set is installed, the switch is on the POWER UNIT.

2. If the frequency of the station to be received is known, set the following controls in the INDICATED POSITION-

3. Set FREQUENCY BAND switch to the band number that includes the frequency of the station desired.

4. Refer to calibration chart and set tuning dial to the position indicated by the chart.

5. Advance sensitivity control until perceptible noise is obtained. Adjust ANTENNA TRIMMER, and R.F. TRIMMER for maximum noise output. Be careful not to advance the SENSITIVITY CONTROL too far, because too much noise will MASK the signal.

6. Increase REGENERATION control until a double CLICK is heard when the O.S.C. TEST button is pressed and released indicating the director is oscillating.

7. Reset TUNING control until desired signal is heard, then adjust ANTENNA TRIMMER and R.F. TRIMMER until maximum signal is obtained.

8. On RAL only. Adjust FREQUENCY VERNIER control until the desired beat note is heard.

10. Place AUDIO TUNING switch ON. Select the desired AUDIO RANGE, 450-770 or 770-1,300. Adjust AUDIO TUNING to the selected audio signal frequency. With the RAL, the FREQUENCY VERNIER may be used for the final adjustment.

TUNING FOR M.C.W. VOICE SIGNALS

1. Procedure is the same as outlined for C.W. reception, except that the REGENERATION control should be adjusted to a point just below oscillation.

2. To adjust the REGENERATION control properly for and MOD.-C.W., increase the REGENERATION control until a click is just heard when the O.S.C. TEST button is pressed. Now retard the REGENERATION control until the click does not appear when you press the test button. The regenerative CONTROL is set just below the point where the set will break into oscillation.

3. The RAK/RAL receivers are not expressly designed for voice or other modulated C.W. reception. With the RAL, the low-pass filter cuts off all audio signals above 1,200 cycles, and this results in considerable distortion.

THE RAO-RBH RADIO RECEIVERS

The RAO-RBH radio receivers are very similar in panel design and tuning control arrangement. Electrically, the two receivers have variations in component parts and circuit design to accommodate differences in frequency bands. But the tuning and operating procedures for the two are nearly the same.

The RAO has a frequency range from 540 to 30,000 kcs. in five bands, and the RBH has a frequency range from 300 to 1,200 and 1,700 to 16,000 kcs., also in five

699198°-46-21

Superheterodyne circuits are used in each receiver. They contain a beat frequency oscillation for C.W. reception and a crystal filter in the intermediate frequency stages to eliminate interfering signals when the sets are operating on C.W. The crystal filter circuit is usually turned off for VOICE reception, because the extreme selectivity when the crystal filter is ON will not permit intelligible voice signals to come through.

Provisions are made for headset and loudspeaker outputs. The headset jack is on the front of the operating panel, while two speaker outlets are on the back of the cabinet. The receiver is designed to use a Navy Type CNA-49106 loudspeaker.

Do not place the loudspeaker on the top of the receiver cabinet, because speaker vibrations may cause microphonic noises in the form of "mechanical feed-back" to distort the receiver's signals.

Since the RAO receiver tunes over the broadcast band, and is also adaptable for use with a loudspeaker, it is often used for program entertainment.

The receivers have their own built-in power supplies, and can be operated from any 115/120 volt, 50/60 cycle single-phase line supply.

The antenna length used with either receiver is not critical. A single wire varying in length from 50 to 20 feet is satisfactory. A low-impedance transmission line of not less than 70 ohms may be used to connect the antenna to the receiver.

OPERATION OF THE RAO-RBH RECEIVER

M.C.W. OR VOICE RECEPTION

1. Set the following controls in the indicated positions:

2. Turn the BAND CHANGING switch to the correct band, and set the MAIN TUNING knob in the position indicated on calibration card for receiving the desired frequency.

3. When the control switch is set for M.V.C. operation, be careful not to advance the R.F. GAIN CONTROL to a point where signal distortion occurs. In general, it is recommended that the A.F. GAIN control be set about half way on, and audio output adjusted by means of the R.F. GAIN control.

5. If a signal is weak and partially obscured by background noise and static, best signal-to-noise ratio will be obtained by turning the TONE towards the LOW position. The most effective setting must be determined by trial.

6. When a signal is accompanied by crashes of static, advance the LIMITER control towards 10. Best setting must be determined by trial. Too much limiter action will impair the audio quality. If static peaks are extremely strong, best LIMITER action is obtained with the CONTROL switch in M.V.C. position . In such cases, both R.F. GAIN and LIMITER controls must be carefully adjusted for optimum operation.

7. After tuning has been completed, switch crystal filter on by setting the PHASING control at any position greater than 0. For M.C.W. operation, a normal setting is 5.

8. The normal setting of the SELECTIVITY control for M.C.W. reception is at the position that affords minimum SELECTIVITY. This position is near the middle of the selectivity scale and is accurately determined by the point where the background noise is maximum.

9. The PHASING control is used to eliminate interfering beat notes that are often present when crystal filter is "in." If the note is above 1,000 cycles, set the control near the mid-point of the dial. If the note is near 300 to 400 cycles, optimum setting is near either end of the dial.

10. For M.C.W. reception, set the tone control in HIGH position. VOICE communication that is

C.W. OPERATION

1. The initial adjustments of the RAO-RBH for C.W. operation are the same as for M.C.W. or VOICE, except that the CONTROL switch must be in C.W.O. position, and the C.W.O. O.S.C. control must be set at mid-scale.

2. The. action of the TONE and LIMITER CONTROLS are the same as for M.C.W., except that both controls may be advanced considerably more.

3. Adjust the C.W. O.S.C. control until you obtain the beat note of the desired pitch.

4. Increase the setting of the PHASING control, and increase the SELECTIVITY by moving the control toward 0. For best operation it will be necessary to try several combinations of these controls.

THE RBA RECEIVER

The model RBA radio receiver is a low frequency T.R.F. receiver designed for VOICE, C.W., and M.C.W. reception. The frequency range is from 15 to 600 kc., in four bands, 15-38, 38-95, 95-235, and 235-600 kc.

While voice reception is possible, many natural characteristics are lost due to the high selectivity and the filters employed in the r.f. stages. When attempting to receive a voice message, the AUDIO switch, NO. 10, should be in the BROAD position. For C.W. reception it should be set for SHARP reception.

A beat-frequency heterodyne OSCILLATOR is incorporated into the circuit for C.W. reception. The oscillator is ganged to the MAIN TUNING CONTROL, 13, and is automatically tuned to the correct frequency to produce a beat note of 1,000 cycles for each setting of the r.f. stages.

The selection of the FREQUENCY BAND is accomplished by rotating a four-position switch. All r.f. and oscillator coils are changed by the movement of this switch.

The MANUAL GAIN CONTROL regulates the gain in the r.f. and a.f. stages. An additional gain control is geared to the main tuning control, so that as the receiver is tuned toward the high end of the band, the volume is reduced. This arrangement insures a uniform output over the entire tuning range.

An OUTPUT LIMITER is used in the circuit to prevent sudden crashes of static from reaching the earphones.

The automatic regulation of the receiver's output volume is a unique feature of this set, because it permits the use of any number of headphones between 1 and 20 without material loss in the output volume.

Legend for Figure 173.

INSTRUCTIONS FOR OPERATING THE RBA RECEIVER

TUNING FOR C.W. OPERATION

1. Set the following controls in the indicated position:

2. Turn BAND SWITCH to the desired frequency band.

3. Turn MAIN TUNING dial to a signal near the high frequency end of the band. If no signal can be found near this setting, turn the MAIN TUNING dial to a point of maximum noise.

5. Adjust ANT. COMP. to resonance as indicated by a maximum signal. The signal strength at this point should drop off sharply at each side of this resonant point. If this point cannot be found, move (ANT.) CPLG. control to position 4 and then successively to 3, 2, and 1, if necessary, to resonate the antenna circuit. The normal setting of this control with most antennas will be 4 or 5. After one tuning adjustment on a fixed antenna has been made, further adjustments are usually unnecessary.

6. Adjust MAIN TUNING dial until a maximum signal is heard in the headset, or indicated on OUTPUT meter. To activate the OUTPUT meter turn ADD DECIBELS SWITCH to 30. If a readable deflection is not obtained with the 30 setting, move the switch successively to 20, 10, or DIRECT as is necessary to obtain a good reading, but no further.

7. Set OUTPUT LEVEL control to a point where the audio volume is of the desired level. If a strong signal causes distortion in the audio signal, reduce the setting of the GAIN control, and then readjust OUTPUT LEVEL to the desired volume.

8. If crashes of static are objectionably strong, throw O. L. switch to ON position.

9. When interfering tones appear with the C.W. beat note, move the AUDIO switch to SHARP. This will cut out practically all but the 1,000 cycle beat note.

TUNING FOR M.C.W. AND VOICE RECEPTION

1. Set all controls as listed in paragraph 1 for C.W. tuning, except RECEPTION switch, which should be set on MOD.

2. Repeat all other tuning steps, 2 through 8. If the output limiter circuit interferes with intelligible reception of audio signals, place the 0. L. switch in the OFF position.

THE RBB-RBC RADIO RECEIVING SETS

The RBB-RBC radio receiving sets are companion receivers designed to cover a frequency range of 0.5 to 4.0 mc for the RBB and 4.0 to 27.0 mc. for the RBC. Many sections of the two receivers are identical and can be interchanged. The chief variations are in the component parts of the tuned radio frequency stages.

The sets are usually installed in pairs, giving a complete frequency coverage from 0.5 to 27 mc. Signals of C. W., M.C.W., and VOICE may be received by either.

POWER SUPPLIES are separate from receivers, and can be installed behind, to the side of, or below the receiver cabinets in the space available. They may be operated from 110/120 volt, 60-cycle, single-phase power lines.

The OUTPUT CIRCUITS are designed to accommodate from one to twenty pairs of 600-ohm headsets with only a slight reduction in volume. This feature makes it possible to use these receivers to feed several remote radio-phone stations about the ship.

Both sets contain several auxiliary circuits to aid you in receiving code and voice communications under adverse operating conditions. The OUTPUT LIMITER circuit prevents strong crashes of static from reaching the headset. The SILENCER CIRCUIT blocks the receiver and keeps background noise at a minimum when the receiver is in stand-by condition.

The AUDIO SELECTIVITY FILTER, used only with C.W. reception, limits the audio output sharply to a 1,000 cycle beat note, thus further reducing the extraneous noises.

Both receivers may be operated from a single antenna. but when this is done, a link coupling inside each receiver cabinet must be opened to insert a decoupling resistor in the antenna circuit. This prevents one receiver from interfering with the operation of the other.

Legend for Figure 174.

USE OF SPECIAL CONTROLS

ANTENNA COMPENSATOR:

When you have changed frequency bands, a signal should be tuned in near the high frequency end of the band. The ANTENNA COMPENSATOR should then be adjusted for a maximum signal strength.

ZERO SET:

The INPUT meter is set to "0" with the ZERO SET control-tune the receiver to a minimum signal at some point NEAR the location of the signal, and then adjust the ZERO SET until the INPUT meter indicates "0."

The normal position of this switch while operating is OFF. When you desire an OUTPUT meter reading, turn the ADD DECIBELS switch first to 30. Advance the switch to 20, 10, and DIRECT only when you are sure the signal will not overload and injure the meter.

RADIO SELECTIVITY: The initial tuning of the receiver is usually done with switch in BROAD position, and then advanced to MEDIUM and SHARP for the final adjustments in tuning. For VOICE reception, this switch may require a MEDIUM or BROAD setting. Attempts to perform initial tuning with the RADIO SELECTIVITY control in SHARP position may cause you to pass over a signal.

SILENCER:

The silencer circuits reduce the receiver's audio output to zero when no signal is being received. Advance the SILENCER control just enough to keep down set and background noises when the receiver is in stand-by condition, but not so far as to BLOCK the signal. The SILENCER control is operative only when the RECEPTION switch is in MOD.-A.V.C.-SIL. position.

RECEPTION SWITCH:

MOD.-A.V.C.-SIL.: This position is used principally when the receiver is in stand-by condition on voice communications. Do not attempt to tune set when the control is set in this position unless SILENCER CONTROL is set at zero.

MOD.-A.V.C.: This is the normal operating setting for VOICE and M.C.W. signals. May be left in this position during the tuning of the set for VOICE and M.C.W. signals.

MOD: This setting may be used for reception of VOICE and M.C.W. signals when fading is not serious. This setting is recommended for tuning, especially for inexperienced operators.

C.W.-O.L.: Normal operating setting for the reception of C.W. signals. The OUTPUT LIMITER'S effects, on this mode of reception, is similar to A.V.C. action. With this setting, the INPUT meter is inoperative. Operate NOISE LIMITER AND AUDIO SELECTIVITY With the FREQUENCY VERNIER until the best copyable signal is received.

AUDIO SELECTIVITY: When objectionable background noises interfere with receiving C.W. signals, set this control on SHARP. adjust FREQUENCY VERNIER until the 1,000 cycle note is obtained.

TUNING PROCEDURE FOR C.W. OPERATION

1. Set the following controls in the indicated position:

2. Tune in a signal, or set TUNING dial to a position of maximum noise near the high frequency end of the band you have selected. Adjust ANT. COMP. for a maximum signal as indicated by the OUTPUT meter or sound in the headset. Further adjustment of the ANT. COMP. is unnecessary as long as you operate on the one frequency band. Changing frequency bands requires further adjustment.

4. Tune in desired station. The correct setting of the tuning dial will be indicated by a maximum deflection of the INPUT meter needle.

5. Set RADIO SELECTIVITY Switch successively to MEDIUM and SHARP, and make final tuning adjustments until a maximum indication is obtained on the INPUT meter.

6. Adjust OUTPUT LEVEL, and operate ADD DECIBEL switch until the desired output volume of sound is obtained.

7. Turn NOISE LIMITER to ON, RECEPTION switch to C.W.-O.L., and FREQUENCY VERNIER to "0."

8. If considerable noise is present with the C.W. beat-notes, place the AUDIO SELECTIVITY switch in SHARP position. Make slight adjustments of the FREQUENCY VERNIER until a pure beat note is obtained. When the AUDIO SELECTIVITY switch is in BROAD position, the pitch of the beat note may be varied by the FREQUENCY VERNIER.

9. Make final adjustments of GAIN control if an extremely strong signal is causing distortion. Set the OUTPUT LEVEL control to a position that produces the desired audio level.

TUNING PROCEDURE FOR M.C.W. AND VOICE RECEPTION

1. Set all controls as listed in paragraph 1 of C.W. tuning instructions, except RECEPTION, which should be set at MOD.

2. Perform all tuning steps, 2 through 6, as listed for C.W. operation.

3. Turn RECEPTION switch to MOD.-A.V.C., and adjust OUTPUT LEVEL until the desired level of volume is obtained.

4. When conditions require stand-by VOICE operation, turn RECEPTION switch to MOD.-A.V.C.-SIL., and adjust SILENCER control until you obtain the

THE RBK RECEIVER

The Navy model RBK receiver is a very high frequency receiver capable of receiving amplitude and frequency modulated signals within a frequency range of 27.8 to 143 megacycles.

The circuit is that of a conventional superheterodyne with one stage of tuned radio frequency preceding the first detector.

To change from the reception of amplitude modulated to frequency modulated signals, you merely turn a switch on the operating panel of the receiver. A single audio frequency amplifier is used for both the A.M. and F.M. sections of the receiver.

699198°-46-22

When the RBK is being operated in an area free from local interference, a single wire about 75 feet long is recommended. Where reception is subjected to strong local interference, and the frequency band of reception is narrow, a dipole antenna of the doubler type is best.

Legend for Figure 175.

OPERATION OF THE RBK RECEIVER

TUNING FOR C.W. OPERATION

1. Set the following controls in the indicated position:

2. Place the A.M.-F.M. switch in A.M. position to receive the type of modulation being transmitted.

3. Operate the TUNING wheel, and set MAIN CALIBRATED scale to approximately the correct position for receiving the desired signal.

4. Adjust ANTENNA control and at the same time readjust the TUNING wheel slightly, until a maximum signal is heard or indicated on the TUNING meter.

5. Adjust the A.F. GAIN for desired volume. Reduce

6. When interfering signals make it necessary, turn SELECTIVITY control to SHARP. Adjust PITCH CONTROL until you obtain the beat note of the desired pitch.

7. Make final adjustments of tuning, gain, pitch, and tone controls until the best copyable signal is obtained.

TUNING FOR M.C.W. AND VOICE RECEPTION

1. Tuning is the same as for C.W. reception, except for the following points-the B.F.O. is OFF, the SELECTIVITY control is usually left in the BROAD position, and the A.M.-F.M. switch is turned to the position to receive the type of modulation being transmitted.

2. Set the TONE control and other tuning signals. The A.V.C. switch must be ON and the R.F. GAIN set at maximum gain.

USE OF THE TUNING METER

1. When using the TUNING meter with A.M. signals, the A.V.C. switch must be ON and the R.F. GAIN set at maximum gain.

2. While using the TUNING meter with F.M. signals, the meter needle will be deflected to one side of zero as you approach the carrier frequency, and to the other side when the carrier is passed. When the receiver is correctly tuned, the meter needle will stand near ZERO.

THE MODEL RCK RADIO RECEIVER

The model RCK radio receiver is one of the newer high frequency types to be introduced to the Navy. It operates in the V.H.F. band between 115 and 156 mc.

This receiver is designed to be used with the TDQ transmitter for short range, line-of-sight, voice communication between ship and aircraft, and between ship to ship.

The TUNING of the receiver is limited to four predetermined channels to match the four frequencies of the TDQ transmitter. The frequency of each channel is CONTROLLED by one of the four crystals in the local oscillator stage. The frequencies of these channels can be changed to any other within the band range merely by switching crystals in the receiver to match the change of crystals in the TDQ.

This receiver has fewer controls and is easier to operate than many Navy types. It is designed to supply a single set of headphones, and by using a suitable amplifier, it may feed remote stations about the ship.

The ANTENNA used with this receiver is a fixed dipole, connected to the receiver by a 50-ohm coaxial transmission line. The maximum length of the transmission line shall not be over 100 feet, and it is recommended that it be as short as possible.

The POWER SUPPLY is built into the same cabinet as the receiver, and may be operated from any 110/120 volt, 55/60 cycle, single-phase power source. The power consumption is about 110 volts, and the set is protected by two 3-ampere fuses.

Legend for Figure 176.

699198°-46-23

INSTRUCTIONS FOR OPERATION OF THE RCK RECEIVER

TUNING FOR M.C.W. AND VOICE OPERATION.

1. Set the following controls in the indicated position:

2. Release DIAL LOCK and set CHANNEL switch to the desired channel.

3. Refer to calibration card and adjust dial until a maximum indication is obtained on the INPUT meter.

4. Turn NOISE LIMITER-OUTPUT METER switch to O.M. Adjust A.F. GAIN, until the audio output of the receiver is at the desired level as indicated by the OUTPUT meter.

5. If the signal received is very strong, and is causing considerable distortion, reduce the R.F. GAIN CONTROL until an undistorted signal is obtained. Readjust A.F. GAIN for desired audio output.

6. The final setting of the NOISE-LIMITER-OUTPUT METER switch will depend upon the character of the reception Usually it will be set at N.L. For normal operation, it is not advisable to have switch in either O.M. or N.L.-O.M. positions. Turn on output meter only when actually adjusting or checking set.

7. Increase setting of SILENCER control to a point where silent operation is obtained when the receiver is in stand-by condition. Do not increase setting of the SILENCER control so much that it cuts off the first part of the incoming message. Too much silencer action will also block weak signals.

8. The setting of the PHONE control will be according to instructions from the operators at remote radiophone stations. Usually this control will be near maximum, because the earphone level can be reduced at the remote stations also.

9. The A.F. BAND switch is used when you are receiving M.C.W. messages. In the NARROW

INTRODUCTION TO RADIO EQUIPMENT

1. All atoms are composed of _____ and _____.
2. An object becomes positively charged by______and NEGATIVELY charged by______
3. The law of charges states______
4. What is a static charge?
5. What will happen if a copper wire is connected between two static charges?
6. Electrons in motion is the definition of______
7. A coulomb per second is equivalent to an______
8. A volt is the expression of______
9. A. Arrange the following potentials in order from most NEGATIVE to highest positive: -, 75, -135, -2, 425, 0.
  B. What is the magnitude of the potential difference between the highest and lowest value?
10. The opposition of a conductor to the flow of current is______
11. Select the materials from the following list that are considered insulators: Mica, carbon, bakelite, zinc, dry air.
12. Name three types of resistors commonly used in radio circuits.

CHAPTER 2
BATTERIES

1. Any force that tends to keep electrons moving is______
2. What materials are necessary to form a cell?
3. Copper and lead are used to make a cell. Which pole will be positive?
4. The______action within a cell is responsible for causing the current to flow.
5. The dry cell is an example of a______cell, and the storage cell is an example of a______cell.
6. Secondary cells can be, while primary cells cannot.
7. The degree of charge of a storage cell is checked with a______
8. Cells connected in either series or parallel are called______
9. Connecting cells in series increases the______, while connecting cells in parallel increases the available______

CHAPTER 3
CIRCUITS

1. An electrical circuit requires a______for the electrons to follow.
2. In a series circuit, the same current______, of the circuit, while in parallel circuit, the current______with the larger portion flowing through the ______ resistance.
3. What is the resistance of a series circuit that contains the following resistors: 100 ohms, 200 ohms, 300 ohms. If the three resistors are in parallel?

CHAPTER 4
OHM'S LAW

1. State Ohm's Law?
2. A circuit has an emf of 100, and a resistance of 20,000 ohms. What is the current? What is it when expressed in milliamperes?
3. The IR drops about a series circuit are 18 volts, 22 volts, 112 volts, and 84 volts, what is the applied emf?
4. A potential of 2,000 volts is being applied to the vacuum tubes of a transmitter, and a current of 300 milliamperes is flowing, what is the power being dissipated?

CHAPTER 5
MAGNETISM

1. Make a drawing of an unmagnetized and magnetized bar showing the probable arrangement of the molecules.
2. The magnetic flux is another name for______
3. The flux is said to flow from______to______
4. Steel and almico are materials used to make______ magnets, while soft iron and permalloy are used to make
5. The term used to express a metal's ability to conduct magnetic flux is______. Retentivity expresses the metal's ability to______

CHAPTER 6
ELECTROMAGNETISM

1. If the current in a conductor is slowing in a wire TOWARD YOU, what is the direction of the field?
2. What effect does the forming of a conductor into a coil have on the magnetic field?
3. What is the rule for finding the north pole of a coil carrying a current?
4. Placing an iron core in a coil serves to______the flux.
5. The cores used in electromagnets must have______ retentivity.
6. What device in Navy transmitters and receivers makes special use of electromagnets?

CHAPTER 7
GENERATORS

1. List the three factors that must be present before induction can take place.
2. Name the four parts of a generator.
3. What type of current is generated by the generator in figure 59?
4. What is the difference between an alternating current and a direct current?
5. a. A current is said to have a frequency of 60 cycles. What does it mean?
  b. How many sine waves are completed each second?
6. State the range of audio frequencies. Radio frequencies?
7. What is the relationship of the expression "cycle" to kilocycle and megacycle?
8. What parts are different in a d.c. generator than in an a.c. generator? What do the parts in a d.c. generator do?
9. What is a pulsating d.c.? Answer by making a drawing.

CHAPTER 8
MOTORS

1. How does the law of "likes" and "unlikes" apply to a motor in getting it to turn?
2. Name the four major parts of a motor. 3. Where are motors used in your communication equipment?

CHAPTER 9
MORE ABOUT INDUCTION

1. Define self induction.
2. What is a counter emf?
3. What does Lenz's Law say about counter emf?
4. What factors determine the inductance of a coil?
5. a. What is reactance? b. What factors determine the magnitude of reactance of a coil?
6. What is the reactance of a 0.01 henry coil to a current with a frequency of 100 cycles? 1,000,000 cycles?
7. What is the basic physical difference between an a.f. choke coil, and an r.f. choke coil?
8. a. What is mutual induction? b. What type of electrical instrument makes wide use of mutual inductance?
9. You have an r.f. and an a.f. transformer. How can you determine which is which?
10. A transformer has 100 turns on the primary and 300 turns on the secondary. Is it a step-up or step-down? What is the turns ratio?

CHAPTER 10
THE CONDENSER

1. What is the general physical structure of a condenser?
2. Name four types of condensers used in radio circuits.
3. What type of condenser is used in tuning your receiver?
4. What unit is used to describe the "electrical size" of a condenser?
5. What is the relationship of condenser reactance to frequency?
6. How is it possible for a condenser to conduct a.c. but completely block the flow of d.c.
7. a. How does a condenser charge? b. When is it fully charged?

CHAPTER 11
RESONANCE

1. The "natural frequency" that an object will begin to vibrate is said to be the______frequency of the object?

2. The resonator used to re-enforce a violin string's vibration;is a ______, and the resonator used with a pipe organ is a ______, while the resonator used in radio circuits is a ______and______connected in either series or parallel.

CHAPTER 12
THE VACUUM TUBE

1. Name the four principle parts of a diode vacuum tube.
2. When a filament is heated to red heat, ______of the metal and form a______about the metal.
3. If a negative potential is placed on the plate of the diode the electrons will be______from the plate, but if a positive potential is placed on the plate the electrons will______ the plate.
4. Increasing the positive potential on the plate of the diode, ______the flow of electrons to the plate.
5. What happens to the flow of current through a diode, if a.c. is placed on the plate of the diode?
6. Why may a diode be considered a one-way street?
7. Where will you find diode vacuum tubes used in your radio equipment?

CHAPTER 13
AMPLIFIER TUBES

1. How does the physical structure of a triode vacuum tube differ from a diode?
2. How does the grid control the flow of current from the cathode to the plate?
3. The bias voltage is a ______potential placed on the grid of a vacuum tube to______the flow of current.
4. The flow of current to the plate of the vacuum tube can be CONTROLLED by regulating the grid voltage or plate voltage. Which is the most effective? Why?
5. The ratio of the grid's ability to the plate's ability to control the flow of plate current is known as the______or______ of the tube.

CHAPTER 14
MORE AMPLIFIER TUBES

1. The interelectrode capacitance of a triode was remedied by placing a______between the plate and control grid. The new tube is called a______
2. In the new tube, the high velocity electrons arriving at the plate knocked other electrons off the plate to create______ Many of these electrons flow to the______grid causing a serious distortion in the signal.
3. The defect of the tetrode was cured by placing a______ between the plate and the screen grid. This new grid is called a______, and the tube itself is called a______
4. The suppressor grid usually operates at the same potential as the______, and therefore cures the effect of secondary emission by forcing the electrons.
5. In a pentode, the screen grid corrects the ______and the suppressor grid the______.
6. The amplification factor of a pentode is (much higher) (much lower) (the same) than a triode.
7. The two chief advantages of a pentode are:
8. In a beam power tube, the suppressor grid is replaced by
9. The beam power tube has most of the advantages of the pentode, but has the additional advantage of being able to deliver large ______with a small driving power.
10. Low frequency, high power transmitting tubes are usually (triodes) (pentodes).
11. The elements within a transmitting tube are usually (larger) (smaller) than in tubes used with receivers.
12. Why must you carefully watch a vacuum tube whose plate is operating at a dull cherry red?
13. What does a blue haze between the cathode and plate usually indicate?

CHAPTER 15
JOBS OF VACUUM TUBE

1. List the four major uses of a vacuum tube in radio equipment.
2. In rectifiers, the vacuum tube changes______to______
3. The filter of a power supply has the duty of______.
4. If 1 volt a.c. is placed on the grid of a vacuum tube and 40 volts a.c. appears in the plate circuit of the tube, the vacuum tube has amplified the voltage ______times.
5. The principle difference between a r.f. amplifier and an a.f. amplifier is in the devices used to______the stages.
6. A voltage amplifier is designed to______, while a power amplifier is designed to______
7. The function of vacuum tube in an oscillator is to______ to the oscillator circuit to keep the oscillations going.
8. In a detector circuit, the vacuum tube helps to separate the from the______of the carrier wave.

CHAPTER 16
BACKGROUND TO MODERN RADIO

1. A message is carried from a transmitter to receiver by ______waves.
2. Radio waves are vibrations in the
3. The radio frequency waves that are responsible for bringing a message to your transmitter are commonly called waves.
4. Radio waves travel at the speed of______
5. The frequency ranges for the seven Navy bands (VL, L, M, VH, UH, SH, and MICROWAVE) are:
6. The commercial broadcast band is included in the______ band.

CHAPTER 17
INTRODUCTION TO TRANSMITTERS

1. a. The three stages of a typical Navy transmitter are b. The duty of the second stage is to______
2. Make a drawing that will show the nature of the wave formed by a C.W. transmitter.

CHAPTER 18
INTRODUCTION TO RECEIVERS

1. The five tasks a receiver must do are:______
2. The receiver's antenna, with the electromagnetic carrier waves act as a______
3. The emf induced in a receiver's antenna has the (same) (different) frequency as sent out by the transmitter.
4. The field strength of a carrier wave is expressed in______ per meter length of antenna.
5. The ability of a receiver to amplify a signal is referred to as the______of the receiver.
6. When you tune a receiver, you adjust the resonant frequency of the receiver to______the frequency of the transmitter.
7. The selectivity of a receiver refers to the ability of a receiver to______
8. A receiver used to pick up C.W. messages may be (more) (less) selective than that one used to receive voice messages.
9. Verniers, band-spreaders, and tuning indicators are devices to aid you in______your receiver.
10. The______vacuum tube usually is used in the r.f. sections of a receiver.
11. In the detector stage, the______is separated from the ______of the carrier wave.
12. Draw a block diagram of a tuned radio frequency receiver.
13. Draw a block diagram of a superheterodyne receiver.
14. What is a beat note?
15. The intermediate frequency stages of a superheterodyne receiver are tuned to a frequency of 465 kc. If the incoming signal is 17,100 kc., what must the frequency of the local oscillator be, if the beat note is equal to the difference in the two frequencies?
16. Receiver calibration cards are______of where to find a certain station.
17. The volume control on the Navy receivers is (similar)_ (entirely different) from the one on a home receiver.
18 The r.f. gain control is used to______in the r.f. stages of the receiver.

CHAPTER 19
REMOTE CONTROL SYSTEM

1. A key control panel has provisions for______ and______the transmitter.
2. The six parts of a radiophone unit are:
3. Transfer panels are actually______. Connections on the transfer panels are made with______
4. Identify where each of the following relays are used: keying; control relays; sequency closing.

CHAPTER 20
THE ANTENNA

1. An antenna is a wire cut to the correct length so it will radiate ______the energy from the transmitter.
2. A dipole is always equal to______
3. In a center fed dipole, the impedance is the (greatest) (least) at the ends, and the current is (greatest) (least) at the center.
4. The electromagnetic field is (greatest) (least) at the center of the dipole.
5. Standing waves are______and______fields surrounding the dipole.
6. The actual length of a transmitter is approximately______ percent______than a half wave length.
7. A Hertz antenna is any antenna equal to approximately a
8. A Marconi antenna is equal to approximately______ wave length.
9. Antenna tuning circuits are used to correct the______
10. Four common types of transmission lines are:
11. A resonant line (does) (does not) have standing waves distributed throughout its length.
12. A non-resonant transmission line is terminated by an impedance ______to that of the line.

699198°-46-24

CHAPTER 21
WAVE PROPAGATION

1. The ground wave moves______, while the sky wave moves______
2. The ground wave is used for short range communication using low power with (high) (low) frequency, and long range communication with (high) (low) power, and (high) (low) frequency.
3. The skywave is used for long range (high) (low) frequency daylight communication.
4. Communication between airplanes in flight is an example of (direct) (ground) (surface) contact.
5. The tropospheric wave is the portion of the ground wave subject______conditions.
6. Long range communication with frequencies in the 18 to 300 kc. band is obtained by using (high) (low) power.
7. The ionosphere is an______layer of the atmosphere existing between the approximate limits of_______miles above the earth.
8. The ionosphere is caused by______and______ radiations from the sun______
9. The ionosphere is (static) (constantly changing).
10 The layers of the ionosphere present during the daylight are:
11. Usually only the______layer is present at night with an occasional______
12. The two general effects of the ionosphere on the skywave is to______and
13. The critical frequency is______and______
14. Variations in the critical frequency are the cause of variations in the______
15. The critical frequency (is) (is not) affected by the hour of the day.
16. The increased ionization during the day has three effects on the sky wave. They are______
17. The presence of the______layer during the daylight hours makes long range,______frequency communications possible.
18. The area between the end of the ground wave, and the position the skywave returns to the earth is called the______
19. Extremely long range communication is permitted by______ refraction and reflection.
20. Fading is usually the result of two waves arriving at a receiver (in) (out) (varying) phase.

CHAPTER 22
NAVY TRANSMITTERS

1. You tune a transmitter to get maximum______from transmitter to antenna.
2. A straight-through transmitter is one where all stages are tuned to the frequency of______
3. Resonating a stage is another name for_______a stage.
4. What devices indicate when a stage is correctly tuned?
5. Resonance in a plate circuit is usually indicated by a______ in the plate current meter.
6. Two indications of resonance in the antenna circuit are ______antenna current, or a (increase) (decrease) in plate current of the power amplifier.
7. Frequency doubling, and frequency multiplying consists in tuning the amplifier stages to one of the being generated by the oscillator.
8. The frequency meter is a device used to______the frequency of the______

CHAPTER 23
NAVY RECEIVERS

No questions on tuning of Navy receivers.

ANSWERS TO QUIZ

CHAPTER 1
WHAT IS ELECTRICITY?

1. Electrons-protons.
2. Losing electrons-gaining electrons.
3. Likes repel, unlikes attract.
4. An object that has gained or lost electrons.
5. Electrons will move through the wire and equalize the charges.
6. An electric current.
7. An ampere.
8. Potential.
9. a. -135, -20, -2, 0, 75, 425.
b. 560 volts.
10. Resistance.
11. Mica, bakelite, dry air.
12. Carbon, wire wound, variable.

CHAPTER 2
BATTERIES

1. An EMF.
2. Two dissimilar metals and an electrolyte.
3. Copper.
4. Chemical.
5. Primary-secondary.
6. Recharged.
7. Hydrometer.
8. Batteries.
9. Voltage, current.

CHAPTER 3
CIRCUITS

1. Complete path.
2. Flows through all parts-divide-smaller.
3. 600 ohms, 54.5 ohms.

CHAPTER 4
OHM'S LAW

1. The current flowing in a circuit is proportional to the voltage and inversely proportional to the resistance.
2. 0.005 amperes-5 milliamperes.
3. 246 bolts.
4. 600 watts.

CHAPTER 5
MAGNETISM

1. Check your drawings with figures 35, 36.
2. The magnetic field.
3. From North to the South.
4. Permanent-temporary.
5. Permeability-retain its magnetism.

CHAPTER 6
ELECTROMAGNETISM

1. Clockwise.
2. Concentrates the field.
3. Wrap your left hand about the coil with the fingers pointing in the direction of the current. The thumb will point to the North pole.
4. Concentrate.
5. Low.
6. Relays.

CHAPTER 7
GENERATORS

1. A magnetic field, a conductor, and a relative motion between them.
2. Armature, field coils, slip rings, brushes.
3. Alternating.
4. Alternating current flows in two directions, direct current only one.
5. a. The current starts at zero, rises to maximum positive, falls to maximum negative and back to zero 60 times a second.
b. 60.
6. 20 to 20,000 cycle. 20 kc. to 30,000 mc.

CHAPTER 8
MOTORS

1. The magnetic field of the armature is alternately attracted and repelled by the field of the stator causing the armature to rotate.
2. Armature, stator, commutator, brushes.
3. To drive the generators in a motor generator set, and to run ventilating fans to cool the transmitter.

CHAPTER 9
MORE ABOUT INDUCTION

1. The ability of a current flowing in a coil to induce a voltage in the coil itself.
2. The voltage of self induction.
3. The induced voltage opposes the voltage that created it.
4. Number of turns of wire per inch, diameter, number of layers of windings, kind of core.
5. a. Reactance is the opposition of a coil to the flow of an alternating current.
b. Inductance of the coil, frequency of the current.
6. 6.28 ohms, 62,800 ohms.
7. An a.f. choke coil has an iron core, while a r.f. choke coil has an air coil.
8. The ability of one coil to induce a voltage in another coil. Transformers.
9. An a.f. transformer will have an iron core, and a r.f. transformer will have an air coil.
10. Step up. One to three.

CHAPTER 10
THE CONDENSER

1. Two metal plates separated by an insulator.
2. Paper, mica, electrolytic, variable.
3. Variable.
4. The farad.
5. Higher the frequency the lower the reactance.

CHAPTER 11
RESONANCE

1. Resonant.
2. Wooden box, pipe, a coil and condenser.
3. Work together.
4. Inductance, capacity.
5. Decrease.
6. Coils.
7. Resonant frequency.

CHAPTER 12
THE VACUUM TUBE

1. Plate, cathode, glass envelope, and a vacuum.
2. Electrons boil out, cloud.
3. Repelled, move to.
4. Increases.
5. Current will flow from cathode to plate on positive half cycles, and not on negative half cycles.
6. Because current will flow from cathode to plate only.
7. In power supplies.

CHAPTER 13
AMPLIFIER TUBES

1. A grid is placed between the cathode and the plate.
2. A negative grid repels the electrons back to the cathode. The more negative the grid the stronger the repulsion.
3. Negative, reduce.
4. Varying the grid voltage. Because the grid is so much closer to the cathode.
5. Amplification factor, Mu.
6. A.C. plate resistance.
7. Interelectrode capacitance.
8. Unwanted oscillations.

CHAPTER 14
MORE AMPLIFIER TUBES

1. Grid, tetrode.
2. Secondary emission. Screen grid.
3. Grid, suppressor, pentode.
4. Cathode, back to the plate.
5. Interelectrode capacitance, secondary emission.
6. Much higher.
7. High sensitivity, low interelectrode capacitance.
8. Beam forming plates.
9. Power.
10. Triodes.
11. Larger.
12. Because a slight addition of current will destroy the tub(c
13. The tube is "gassy."
14. In a Vacuum Tube Manual.

CHAPTER 15
JOBS OF A VACUUM TUBE

1. Rectifiers, amplifiers, oscillators, detectors.
2. Alternating current to direct current.
3. Smooth out the ripples in the d.c.
4. 40.
5. Couple the stages.
6. Increase the voltage, increase the current.
7. Supply the energy.
8. Audio component, radio frequency portion.

CHAPTER 16
BACKGROUND TO MODERN RADIO

1. Electromagnetic.
2. Ether.
3. Carrier.
4. Light.
5. Check your answer with the table on page 162.
6. Medium frequency.

CHAPTER 17
INTRODUCTION TO TRANSMITTERS

1. a. Oscillator, buffer, power amplifier. b. Isolate the oscillator from power amplifier.
2. Check your drawing with figure 118.
3. Modulation.
4. Buffer.
5. Audio oscillator.

CHAPTER 18
INTRODUCTION TO RECEIVERS

1. Check your answer with page 172.
2. Generator.
3. Same.
4. Microvolts.
5. Sensitivity.
6. Match.
7. Tune in one transmitter and tune out another.
8. More.
9. Tuning.
10. Pentode.
11. Audio component, radio frequency component.
12. Check your drawing with figure 127.
13. Check your drawing with figure 128.
14. A note formed by beating two vibrations of different frequencies against each other.
15. 17,565 kc.
16. Accurate records.
17. Similar.
18. Control the gain.
19. Same.
20. Adjusting.
21. Noise and static.
22. Is properly tuned.
23. On.

CHAPTER 19
REMOTE CONTROL SYSTEM

1. Starting, stopping, and keying.
2. Handset, carrier off-on, earphone level, key circuit off-on, noise suppressor control, start-stop.

CHAPTER 20
THE ANTENNA

1. Efficiency.
2. A halt wave length.
3 Greatest, greatest.
4. Greatest.
5. Electromagnetic, electrostatic.
6. 5% shorter.
7. One half wave length.
8. One quarter wave length.
9. Electrical length.
10. Open two wire, coaxial calls, twisted pair, shielded pair.
11. Does.
12. Equal.

CHAPTER 21
WAVE PROPAGATION

1. Along the surface of the earth-Upward and outward.
2. High, high, low.
3. High.
4. Direct.
5. Atmospheric.
6. High.
7. Ionized, 30-350.
8. Ultra violet, particle.
9. Constantly changing.
10. D, E, F₁, F₂.
11. F, Sporadic E.
12. Absorb, refract.
13 The highest frequency radiation that can be sent directly upward and still be returned to the earth.
14. Ionosphere.
15. Is effected.
16. a. Causes sky wave to return to the nearer point of transmission. b. Absorbs more energy from the sky wave. c. F₁-F₂ layer makes long range, high frequency communication possible

CHAPTER 22
NAVY TRANSMITTERS

1. Power.
2. The oscillator.
3. Tuning.
4. The meters.
5. Dip.
6. Maximum, increase.
7. Harmonics.
8. Check, oscillator.

INDEX

* U. S GOVERNMENT PRINTING OFFICE: 1946-699198