CHAPTER 22
NAVY TRANSMITTERS
WHY YOU TUNE A TRANSMITTER

You TUNE a transmitter to get MAXIMUM POWER from the transmitter into the antenna. This can be likened somewhat to adjusting a heating plant to get the maximum amount of heat into the radiators.

You adjust a heating plant by opening and closing valves which regulate the fuel and air supply. If these are not in PROPER PROPORTIONS, you don't get maximum heat. Also, if some of the valves in the steam line are opened too widely, and others closed too tightly, the radiators can't do their best job of heating. Suppose you want to turn down the heat. There are two common ways of doing this-turn off the radiator, or reduce the fuel input to the boilers.

Now notice the comparison between a heating plant and a transmitter. The POWER (fuel) to operate the transmitter might be considered the pilot that STARTS the transmitter's operation. Now, unless the CORRECT

WHAT IS TUNING?

A transmitter is tuned by setting each stage of the transmitter to the frequency of oscillations generated by the oscillator. Here is how this procedure works out.

You are instructed to tune up on a frequency of 3,746 kilocycles. Follow the steps shown in figure 158. The

Next, step 2, tune the stage following the oscillator to the same frequency, 3,746 kcs. The 2ND INT. AMPLIFIER, step 3, is next tuned to a frequency of 3,746 kcs., followed by the POWER AMPLIFIER stage, and then the ANTENNA CIRCUIT.

Briefly, here's the routine of tuning the AF STRAIGHT THROUGH transmitter, one that has EACH STAGE tuned to the frequency of the oscillator-first tune the oscillator to the right frequency, and then tune each successive stage after the oscillator to the frequency of the PRECEDING stage.

RESONATING A STAGE

TUNING a stage to the desired frequency is sometimes called RESONATING the stage. Thus the expressions

The RESONANT FREQUENCY of a stage is the FREQUENCY at which it will oscillate. You have had many contacts with RESONANT frequencies. Recall your experience with an automobile. When driving at a certain speed, certain RATTLES and VIBRATIONS would be present. At other speeds, different vibrations and other rattles appeared. It seemed that every speed had its own rattle, and, by knowing your rattles, you could tell your speed.

Why did certain rattles and vibrations appear at one speed and not at others? Because the automobile, when traveling at one speed, produced the frequencies of vibration of some rattles but not of others. At other speeds, other frequencies of vibration were produced.

Similarly, if the oscillator is generating a radio frequency current of 2,136 kc., and the following stage is tuned to 2,251 kc. the stage following will not vibrate, or oscillate, until the oscillator frequency is RAISED to 2,251 kc., or the stage following is REDUCED to 2,136 kc.

In RESONATING a stage, you adjust the variable inductance, or condenser, until the RESONANT frequency of the stage is the same as the one preceding it.

INDICATORS OF RESONANCE

How do you know when a stage is tuned to resonance? The METERS on the operating panel of the transmitter tell you.

Two general classes of meters are used with transmitters-GRID CURRENT meters showing the current flow in the grid circuits, and PLATE CURRENT meters that indicate the current flowing in the plate circuits. In addition, most transmitters have an ANTENNA CURRENT meter to show the current in the antenna circuit.

Here is a general rule for using the meters-GRID current meters show resonance by a MAXIMUM indication, while PLATE CURRENT meters show resonance with a MINIMUM

The tuning controls in figure 159 are indicated by the numerals 1 to 7. They may be marked as follows-

The first step in tuning this arrangement is to set dial 1 to the desired frequency. You will do this by referring to the calibration card, and checking against a FREQUENCY METER. More about this later.

Next, adjust dial 2, until a MAXIMUM indication is obtained on meter A. That shows the OSCILLATOR stage to be TUNED to RESONANCE.

Now, adjust dial 3, until a MAXIMUM indication is obtained on meter B. The 1ST INT. AMPLIFIER is now tuned to resonance.

Adjust dial 4 until a MINIMUM reading is obtained on the PLATE CURRENT meter C. When this is done, a MAXIMUM deflection will be obtained on GRID CURRENT meter D. You have now tuned the 2ND INT. AMPLIFIER to resonance.

Finally, you adjust dial 5, until a MINIMUM indication is obtained on PLATE CURRENT meter E. The power amplifier has also been tuned to resonance.

Notice again how each GRID CURRENT meter gave a MAXIMUM indication, while the PLATE CURRENT meter gave a minimum indication as the stages were tuned to resonance.

RESONATING THE ANTENNA CIRCUIT

Resonance indications in the antenna circuit vary with the type of TRANSMITTER, the FREQUENCY of emission, the LENGTH and TYPE of antenna used. Resonance in the antenna circuit is sometimes indicated by a MAXIMUM ANTENNA current and at other times by a RISE in the POWER AMPLIFIER PLATE CURRENT, meter E.

Here is the procedure-after tuning the POWER AMPLIFIER to resonance, INCREASE slightly the setting of CONTROL 6, ANTENNA COUPLING. Adjust ANTENNA TUNING, dial 7, until a MAXIMUM antenna current is shown on meter F. If an indication on meter F CANNOT be OBTAINED, resonance in the ANTENNA CIRCUIT will have been achieved when the POWER AMPLIFIER PLATE CURRENT, meter E, stops rising. Remember these two types of indications. You will use both of them.

When the ANTENNA CIRCUIT has been resonated, INCREASE the SETTING of the ANTENNA COUPLING, dial 6, until the POWER AMPLIFIER PLATE CURRENT meter E indicates approximately the proper OPERATING current. READJUST controls 5 and 7 slightly as you increase the setting of control 6, until the proper POWER AMPLIFIER PLATE CURRENT is obtained.

Tuning the power amplifier and antenna requires considerable practice and much care. Remember that it varies from set to set, from one frequency to another, and with the conditions of the seas.

OVERCOUPLING OF POWER AMPLIFIER TO ANTENNA

In tuning, one mistake easily made is to increase the coupling between the POWER AMPLIFIER and ANTENNA CIRCUIT too much. When this happens, the POWER AMPLIFIER stage is detuned, and efficiency goes down. The table on page 283 tells how you may check for the presence of OVERCOUPLING. When you find it, reduce the coupling.

LOADING UP A STAGE

LOADING UP A STAGE is an expression you will frequently hear in connection with tuning a transmitter. Refer back to the adjustment of dial 2 in figure 159. When this dial was set to resonance as indicated by a rise in GRID CURRENT of METER A, you performed the task of LOADING UP the 1ST INT. AMPLIFIER STAGE. Also, when you resonated the 1ST INT. AMPLIFIER STAGE by adjusting dial 3, you LOADED UP the 2ND INT. AMPLIFIER STAGE.

Occasionally you will find it impossible to load up a following stage by resonating the preceding one. The common cause of this failure is lack of coupling between the preceding and following stages. When this happens, call a technician.

OPERATING WITH REDUCED POWER

Often it is desirable to operate the transmitter at less than full power. Some transmitters have special switching arrangements to cut out the last amplifier stage and couple the antenna circuit directly to the 2nd intermediate amplifier. The TBK is an example of this type of transmitter.

Other transmitters require that you reduce the coupling between the power amplifier and antenna circuits. This practice has the effect of permitting less energy to reach the antenna. Remember? This is like turning down a steam valve on a radiator.

Some transmitters allow you to reduce power by turning down the voltage applied to the power amplifier. This method of reduction is more like cutting down heat at the radiator by reducing the fuel supply to a boiler.

It is very important that you know the permissible methods of reducing the output power. Check the instruction books to gain this information.

HARMONICS

You were briefly introduced to the subject of harmonics in chapter 18 on receivers. Now you will get a fuller story of what they are.

You recall that a bell, or tuning fork, gives out a note of the same pitch each time you strike it. If you could take the sound waves apart and examine them, you would find that instead of a single note of one frequency being present, there are several notes of different frequencies.

The note with the LOWEST frequency-usually the STRONGEST note-is called the FUNDAMENTAL, Or the FIRST HARMONIC. As an example, say the fundamental frequency is 500 cycles. Oddly enough, the note with the next higher frequency will have exactly TWICE the frequency of the FIRST HARMONIC, or-500 X 2 = 1,000 cycles. And the frequency of the THIRD HARMONIC will be 3 times the frequency of the first harmonic-500 X 3 = 1,500 cycles. And so on.

This SERIES of HARMONICS goes on up indefinitely, becoming weaker and weaker until their intensity is too weak to be recorded.

Oscillators used with radio circuits also produce a series of harmonic frequencies. For example, if an oscillator has a first harmonic of 2,500 kc., it also has a series of harmonics following it-

Notice how these harmonics are used in the next section.

FREQUENCY MULTIPLYING

- It is easier to design and build a stable oscillator for low frequencies than it is for high frequencies. In addition, if crystals are used to control the oscillator

To overcome this difficulty, oscillators are made to generate a relatively low 1st HARMONIC. The high frequencies are obtained by making the following stages

In figure 160, the oscillator is tuned to the first harmonic, 2,500 kc. The next stage, the DOUBLER, is tuned to the SECOND HARMONIC, 5,000 kc. In the doubler stage, the 5,000 kc frequency ALSO HAS HARMONICS, and as far as the next stage, the tripler, is concerned, the 5,000 kc. frequency can again be considered the FIRST HARMONIC. Therefore, the tripler stage may be tuned to the THIRD harmonic of 5,000 kc.-15,000 kc. Thus, the output of the tripler stage is SIX times the frequency of the oscillator-

2,500 kc. X 6 = 15,000 kc.

You will find this system of frequency DOUBLING and TRIPLING used with several Navy transmitters. Sometimes, the oscillator is followed by a tripler, and then by a doubler stage. The operation is the same whichever the case may be.

PICKING THE CORRECT HARMONIC

The use of frequency multiplying makes it very important for you to understand that an oscillator has MANY HARMONICS. Here is why.

Systems of PICKING and COUNTING the harmonics can easily be developed with the aid of an experienced operator. But until you have developed this technique, you'd better practice resonating the stages VERY CLOSE to the position indicated on the calibration card.

FREQUENCY METER

Frequency meters are just ACCURATELY CALIBRATED OSCILLATORS. You use them to check the frequency of the transmitter oscillator. Briefly, here is what a frequency meter does.

When you wish to check the transmitter's frequency, you first set the frequency meter ACCURATELY to the desired frequency.

The next step is to adjust the oscillator tuning control slightly until the BEAT NOTE DISAPPEARS. The oscillator is now tuned to the correct frequency-you can turn the frequency meter off, and proceed with the tuning of the transmitter.

Be careful that you DO NOT beat a higher OSCILLATOR HARMONIC against the frequency meter, because it, too, will give a ZERO BEAT. That is why it is wise always to set the OSCILLATOR TUNING DIAL as near to the correct frequency as possible by referring to the calibration card.

The way the frequency meter is coupled to the transmitter varies greatly from one installation to another. Therefore, it will be necessary for you to get an experienced operator to explain your setup.

NAVY TRANSMITTERS

The Navy transmitters discussed in the following sections are representative of the most common installation s. Probably you will not find all models on your ship, but it is possible. At least, if you are transferred from ship to ship, you certainly will come in contact with most of them.

The information given for each model is extremely brief. It is little more than an introduction to the sets. Therefore, it is well to refer often to the INSTRUCTION BOOKS for more complete information.

THE TBK-TBM TRANSMITTING EQUIPMENT

The TBK-TBM transmitters are similar in both construction and general appearance. But they differ in that the TBK is intended for C.W. transmission only, while the TBM is provided with a separate MODULATOR for voice M.C.W. communication.

The similarity in construction and design makes it possible to use a single set of instructions for placing

Both the TBK and TBM are capable of tuning over a frequency band from 2,000 to 18,100 kilocycles. The full power output is about 500 watts at low frequencies, gradually decreasing to 300 watts at 18,100 kilocycles.

The frequency of the transmitter controlled by an electron-coupled, master oscillator, followed by doubler stages. The oscillator itself tunes over a range of 1,000 to 2,262.5 kilocycles. The first intermediate stage operates as a STRAIGHT-THROUGH amplifier up to 4,000 kilo-cycles, and as a doubler for frequencies from 4,000 to 9,050 kilocycles. Frequencies above 9,050 kilocycles are obtained by doubling in the SECOND intermediate amplifier. The power amplifier stage operates as a straight-through amplifier over the entire frequency range.

Extreme care must be exercised in tuning the TBK-TBM transmitters not to tune any of the stages to the wrong harmonic. That is especially true in tuning the DOUBLER CIRCUIT. The final setting of the tuning dials will be within a very few scale divisions of the settings indicated on the calibration card.

Provisions are made for low power operation with a nominal output of 75 watts in the range of 2,000 to 9,050 kilocycles. You do this by switching the final amplifier out of the transmitter circuit, and connecting the 2nd intermediate output directly to the antenna circuit.

Legend for Figure 162.

OPERATION OF THE TBK-TBM TRANSMITTERS

GENERAL

1. The lettered controls (A) through (L) are used in TUNING the transmitter. You will use them in ALPHABETICAL ORDER. The meters accompanying the controls indicate when the dials have been properly set.

2. The tuning of all stages, especially the doubler, requires extreme care-you may tune up on the WRONG HARMONIC. Usually you will find the final dial settings to be within a very few scale divisions of the positions indicated on the calibration card. If you find considerable error in the final settings, call someone to check your work.

3. The routing followed in resonating and loading the antenna circuit is subject to considerable variation . It depends upon the frequency of transmission, length of the antenna, and the condition of the sea (whether the ship is rolling and pitching or not) . Therefore, the procedure given here for tuning the antenna circuit is a suggested procedure rather than an absolute pattern to follow.

TUNING PROCEDURE FOR HIGH POWER CW. EMISSION

1. Set the following controls and switches in the indicated positions.

2. Press START button. Adjust GENERATOR FIELD rheostat until plate voltage meter indicates 1,000 volts. Adjust FILAMENT VOLTAGE control until filament meter indicates 10 volts.

3. Set the FREQUENCY METER to the correct frequency. If the frequency meter is coupled to the grid circuit of the master oscillator stage, the frequency meter must be set on the master oscillator frequency. Should the frequency meter be coupled to the output plate circuit of the master oscillator, the frequency meter must be set on TWICE the master oscillator frequency. (Check this coupling system with your chief.)

4. Insert headphone jack in FREQUENCY METER output jack, and adjust MASTER OSCILLATOR, tuning control B, until zero beat is obtained. Be sure you are on the CORRECT harmonic. It will be very close to the setting indicated on the calibration card.

5. Operate TEST KEY. The M. O. PLATE CURRENT should be about 60 ma., and M. O. SCREEN CURRENT near 11 ma.

6. Turn the TUNE-OPERATE switch to TUNING, STEP 2. Increase GENERATOR FIELD rheostat until PLATE VOLTAGE METER indicates 2,000 volts.

7. Operate TEST KEY and adjust DOUBLER, control C, until a maximum indication is obtained on the 1st INT. AMP. PLATE CURRENT meter. The final setting of this control should be within 2 or 3 scale divisions of the position indicated on the calibration card.

8. With test key depressed, tune the 1st INT. AMP.,

9. With the TEST KEY depressed, tune the 2nd INT. AMP., control E, to resonance. It will be indicated by a maximum indication of the P. A. GRID CURRENT meter.

PRECAUTION: Observe the P. A. PLATE CURRENT. If it becomes excessively high, reduce the plate voltage by turning the GENERATOR FIELD rheostat counterclockwise.

10. Adjust POWER AMPLIFIER TUNING, control F, until a minimum indication is obtained on the P. A. PLATE CURRENT meter.

11. Tune the antenna circuit to resonance by varying the ANTENNA TUNING CAPACITOR, control J, and ANTENNA TUNING INDUCTANCE, control K, until a rise in P. A. PLATE CURRENT is indicated. At this point, an indication of current may also be observed on the ANTENNA CURRENT meter.

12. If resonance cannot be obtained, move the ANTENNA FEED, Control F, to the OTHER position, that is, CURRENT to VOLTAGE, or VOLTAGE to CURRENT. repeat the tuning procedure outlined in step 11. If you still fail to obtain resonance, increase the setting of the ANTENNA COUPLING, control H, and repeat steps 11 and 12.

13. If the P. A. PLATE CURRENT meter indicates over 150 ma., reduce ANTENNA COUPLING, control H, and readjust control K, until the minimum P. A. PLATE CURRENT is just slightly less than 150 ma.

14. Set the TUNE-OPERATE switch on OPERATE, and increase GENERATOR FIELD rheostat, until the PLATE VOLTAGE meter indicates 3,000 volts.

15. Close TEST KEY and readjust ANTENNA TUNING capacitor, control J, for a maximum indication on the ANTENNA CURRENT meter. (See NOTE.)

NOTE: Sometimes it is impossible to obtain an ANTENNA CURRENT indication. In such cases, it is necessary to use the P. A. PLATE CURRENT as an indication of resonance. When the P. A. PLATE circuit has been tuned to resonance, ANTENNA RESONANCE will be indicated by a rise in P. A. PLATE, CURRENT to a maximum value. Be very sure that the rise in power amplifier plate current is not due to DETUNING the power amplifier stage.

16. Check for the presence of overcoupling, using the procedure outline on page 283.

ADJUSTMENTS FOR LOW POWER OPERATION

1. Place TUNE-OPERATE switch in TUNING 2 position. Throw the HIGH-LOW POWER switch to LOW position. This action disconnects the POWER AMPLIFIER for the circuit, making the 2nd INT. AMPLIFIER the final amplifier stage.

2. Return TUNE-OPERATE switch to OPERATE position and adjust ANTENNA COUPLING, control H, until the 2nd INT. AMP. PLATE CURRENT does not exceed 150 ma. Reducing coupling may also make it necessary to retune slightly the 2nd INT. AMP. PLATE circuit for a minimum 2nd INT. AMP. PLATE CURRENT indication.

REMOTE OPERATION

1. When the transmitter has been tuned, place the REMOTE-LOCAL switch in REMOTE position. The transmitter can be started, stopped, and keyed from remote stations. When returning or adjusting, it is always best to return the control to LOCAL.

THE TBM MODULATOR EQUIPMENT

The TBM transmitter can be operated independently of the modulator unit. However, when the transmitter is installed with the modulator, the mode of transmission-C.W., M.C.W., or VOICE-is determined by the setting of the EMISSION SELECTOR switch on the modulator unit.

When the EMISSION SELECTOR is set in C.W. position, the operation of the transmitter is independent of the modulator's controls. Start, time, and adjust the transmitter as outlined in the preceding section.

When you are preparing the TBM for M.C.W. and VOICE transmission, reduce the P. A. PLATE CURRENT of the transmitter from 350 to 270 ma., by decreasing the setting of the ANTENNA COUPLING, control H. The modulator is started and stopped simultaneously with the transmitter.

HOW TO ADJUST MODULATOR FOR M.C.W. OPERATION

1. Turn C.W.-M.C.W.-VOICE switch to VOICE.

2. Operate TEST KEY on transmitter, and readjust ANTENNA COUPLING, control H, until P. A. PLATE CURRENT is not over 270 ma.

3. Turn C.W.-M.C.W.-VOICE switch to M.C.W., and key as desired from a local or remote station, as designated by the setting of the REMOTE-LOCAL CONTROL switch on transmitter.

4. Check the modulator's meter readings against the chart on page 259 to determine whether the set is operating properly.

Legend for Figure 163.

TYPICAL MODULATOR METER INDICATIONS

How TO ADJUST TRANSMITTER FOR VOICE OPERATION

1. Turn C.W.-M.C.W.-VOICE switch to VOICE position. Operate TEST KEY on transmitter, and reduce P.A. PLATE CURRENT to 270 ma. by decreasing the ANTENNA COUPLING, control H.

2. Remove HANDSET from microphone hook. Place CARRIER CONTROL switch in MANUAL position. Press the button on the handset and talk into the microphone.

3. Adjust SPEECH GAIN attenuator until PERCENTAGE MODULATION meter indicates the transmitter is being modulated.

4. Do not increase the SPEECH GAIN attenuator beyond a point where the PERCENTAGE OF MODULATION

5. Check the level of sound being received from the receiver. If too low, increase the RECEIVER VOLUME ATTENUATOR.

6. Turn the transmitter's REMOTE-LOCAL CONTROL switch to REMOTE-the transmitter is set for remote operation.

7. Check the meters on the modulator to see that they do not materially exceed the values given in the chart on page 259.

8. Set MANUAL-AUTOMATIC GAIN switch in AUTOMATIC position. This eliminates the need for further adjustments of the SPEECH GAIN ATTENUATOR.

9. Suppose the operator stationed at the MODULATOR desires to exercise control over the remote stations. He can do so by removing the TEST HANDSET from the hook, or by moving the CARRIER CONTROL switch to MANUAL and the TALK switch to OFF. By doing this, the operator can cut off all transmissions from remote stations.

THE TBL RADIO TRANSMITTING EQUIPMENT

The TBL radio transmitting equipment has two different operating panel arrangements. This feature gives the impression that the two types are quite different in circuit design, but actually they are very similar. Models 4, 8, and 9 have one panel arrangement, and 5, 6, 10, and 11 have another. Careful examination of the controls on the two panels will reveal their identity.

Models TBL 10 and 11 are intended primarily for shore installations. The others are intended for smaller surface craft and submarines. In this discussion, only the TBL 5-6 is considered.

The TBL 5-6 is actually two transmitters in a single cabinet. The INTERMEDIATE FREQUENCY section, 175 to

Unlike the TDE transmitting equipment, the TBL sets use common vacuum tubes for all stages of both sections except MASTER OSCILLATORS. The tuning inductances and capacitors belonging to individual circuits are separate. A TRANSFER SWITCH changes the vacuum tube connection from one transmitter section to the other. When the TRANSFER SWITCH is in either position, the controls of one section are inoperative.

All TBL transmitting sets may be used for C.W., M.C.W., or VOICE communication. When VOICE transmission is desired, a Navy Type CRV 50064 speech input equipment must be used.

The nominal output power is 200 watts on C.W., 100 watts for M.C.W., and 50 watts on VOICE. You may reduce the power output on C.W. transmission by turning the plate voltage control counterclockwise, or by decreasing the coupling between the power amplifier and antenna circuits. On M.C.W. and VOICE, it is advisable to reduce the power by decreasing the ANTENNA COUPLING.

A unique method is used to indicate the controls that govern the individual transmitter circuits. The L.F. CONTROLs have a BLUE background, and the H.F. controls a GREEN background. The lettered controls B through M are used to tune the H.F. section, and N through V the I.F. section. Control A is the H.F.-I.F. TRANSFER SWITCH, and W the ANTENNA TRANSFER SWITCH.

COMMON CONTROLS

HIGH FREQUENCY SECTION-TUNING CONTROLS

LOW FREQUENCY SECTION-TUNING CONTROLS

METERS ON THE TBL 5 TRANSMITTING EQUIPMENT

6991980-46-18

OPERATION OF THE TBL-5 TRANSMITTER

GENERAL

1. In this discussion the dial settings indicated on the calibration card are assumed to be correct. Extreme care must be exercised in tuning the H.F. master oscillator doubler circuit that you don't select and tune to the wrong harmonic. If resonance cannot be obtained within two or three dial divisions of the position indicated on the calibration card, recheck the calibration.

2. The method employed in using the frequency meter to check the master oscillator frequency, depends upon the inter-connecting circuits between frequency meter and oscillator. Check with your chief for the proper procedure with your particular installation.

3. The maximum permissible power amplifier plate current varies with the transmitter's frequency. Therefore, it is necessary to check the instruction book of the calibration card for the correct values each time you change frequency or type of emission.

4. The output power of the transmitter can be reduced by decreasing the coupling between the power amplifier stage and the antenna circuit, or by reducing the plate voltage by turning the PLATE VOLTAGE rheostat counter clockwise. The reduction in output power from C.W. to M.C.W. or VOICE operation is usually accomplished by reducing the coupling.

TUNING THE HIGH FREQUENCY SECTION FOR C. W. EMISSION

1. Set the following controls and switches in the indicated positions.

2. Set the following controls in the position indicated on the calibration card for the desired frequency.

3. Press the START button. Then adjust FILAMENT VOLTAGE rheostat until FILAMENT VOLTAGE meter, M7, indicates 10 volts.

4. Set frequency meter to the desired frequency, and with the test key depressed, tune the master oscillator to zero beat. BE SURE you are tuning on the correct harmonic. The final setting of the M.O. TUNING, control C, will be within two or three scale divisions of the setting indicated on the calibration card.

5. When ZERO BEAT has been obtained, depress the TEST KEY. The M.O. SCREEN CURRENT meter should indicate about 11 ma., and the M.O. PLATE CURRENT should be about 40 and 60 ma., depending on the frequency setting of the oscillator.

6. Place the TUNE-OPERATE switch in the TUNING 2 position. Depress the TEST KEY and tune each of the following stages to resonance as indicated. BE VERY CAREFUL in tuning the DOUBLE CIRCUIT, or you may tune on the WRONG HARMONIC. The correct setting will be VERY NEAR the setting indicated on the calibration card.

7. Adjust ANTENNA INDUCTANCE, control K, and antenna CAPACITOR, control L, until a maximum antenna CURRENT indication on meter M13, or an increase in the P.A. PLATE CURRENT, meter M11, is obtained. If no indication can be obtained, or a rise in power amplifier plate current is not observed, slightly increase the setting of the antenna COUPLING, control J, until an indication is obtained.

8. If it is still impossible to obtain an antenna current indication or a rise in power amplifier plate current, change the setting of the ANTENNA FEED, control M, to the OTHER position, and continue the adjustments of controls K and L, until resonance is obtained.

9. As soon as resonance has been obtained, place the TUNE-OPERATE switch in the OPERATE position, then adjust the PLATE VOLTAGE rheostat for a 2,000 volt indication on the PLATE VOLTAGE, meter M10.

10. Increase ANTENNA COUPLING, control J, and readjust controls K and L until a maximum antenna current is obtained with exactly 350 ma. of plate current as indicated by meter M11.

12. Check the P.A. GRID CURRENT, meter M9. If the indication is more than 90 ma., place the P.A. GRID CURRENT, control 13, in the TO LOWER position.

13. Final check. Observe all meter indications. If they are much in error from the indications given on the calibration card, slightly readjust the controls necessary to correct the indications. The P.A. PLATE CURRENT must not exceed 350 ma, with 2,000 volts applied to the plate circuit.

ADJUSTMENTS FOR VOICE EMISSION

1. Tune as outlined for C.W. emission. When tuning has been completed, place the PHONE-C.W.-M.C.W. switch in the PHONE position. Reduce the output power by reducing the setting of the ANTENNA COUPLING, control J, until the proper P.A. PLATE CURRENT indication is obtained for the frequency of transmission.

ADJUSTMENTS FOR REMOTE OPERATION

1. Place the REMOTE-LOCAL switch in REMOTE position. The transmitter then can be started, stopped, and keyed from the remote stations about the ship. Complete supervisory control always remains with the operator at the transmitter regardless of the setting of the REMOTE-LOCAL switch.

TUNING THE LOW FREQUENCY SECTION FOR C.W. EMISSION

1. Set the following controls and switches in the indicated positions.

2. Set the following controls in the positions indicated on the calibration card for the desired frequency.

3. Press the START button, and adjust the FILAMENT VOLTAGE rheostat until a 10 volt indication is obtained on the FILAMENT VOLTAGE, meter M7.

4. Set frequency meter to the desired frequency, and with the TEST KEY depressed, tune the master oscillator to zero beat. Be sure you are tuning to the correct harmonic. The final setting of the M.O. TUNING, control O, will be within two or three scale divisions of the setting indicated on the calibration card. When properly set, the M.O. PLATE CURRENT, meter M2, should indicate 45 ma.

5. Place TUNE-OPERATE switch on TUNING 2, and adjust PLATE VOLTAGE rheostat until an indication of 2,000 volts is obtained on the PLATE VOLTAGE, meter M10, with the TEST KEY up.

6. With the TEST KEY depressed, tune each of the following stages until resonance is indicated.

7. Increase the setting of the ANTENNA COUPLING, control S, by approximately 20 scale divisions.

8. Rotate the ANTENNA TUNING, control R, throughout its entire range for each setting of the

9. Place the TUNE-OPERATE switch in the OPERATE position.

10. Increase the setting of the ANTENNA COUPLING, control S, until the P.A. PLATE CURRENT stops rising. NEVER EXCEED 350 ma. indication on the P.A. PLATE CURRENT, meter M11.

11. Check for the presence of overcoupling as outlined on page 283. If overcoupling is present, reduce the setting of the ANTENNA COUPLING, control S, until the condition is remedied. Don't be surprised if the maximum obtainable plate current without overcoupling is less than 350 ma. Do NOT readjust the P.A. TUNING, control R. It was correctly tuned when the ANTENNA COUPLING was set near zero.

ADJUSTMENTS FOR M.C.W. OR VOICE EMISSION

1. Tune as outlined for C.W. emission. When the tuning has been completed, place the C.W.-M.C.W.-PHONE switch to either M.C.W. or PHONE. decrease the output power by reducing the setting of the ANTENNA COUPLING, control S, until the proper P.A. PLATE CURRENT indication is obtained for the type of emission selected at the frequency of transmission.

ADJUSTMENTS FOR REMOTE OPERATION

1. Place the REMOTE-LOCAL switch in REMOTE position. The transmitter then can be started, stopped, and keyed from the remote stations about the ship. Complete supervisory control always remains with the operator at the transmitter regardless of the setting of the REMOTE-LOCAL switch.

THE TDE RADIO TRANSMITTING EQUIPMENT

The TDE radio transmitter is actually two separate transmitters in a single cabinet. The INTERMEDIATE FREQUENCY units, 300 to 1,500 kc., occupies the section to your right. The HIGH FREQUENCY components, 1,500 to 18,000 kc., are housed in the section to your left. Controls and meters common to both sections are mounted on the middle section of the control panel.

The bottom part of the assembly contains the power supplies, rectifiers, filters, and motor-generator set. Some installations have the power supply and transmitter units separated. This allows the transmitter to be placed on a bench, with the power supply unit in some out-of-the-way place.

The output of the transmitter may be C.W., M.C.W., or VOICE. The nominal output power is 125 watts on C.W., 35 watts on M.C.W., and 20 watts with voice. The output power from either transmitter may be varied from full power to about 1/4 full power by decreasing the ANTENNA COUPLING CONTROL, which is in the antenna circuit of each transmitter.

The antenna circuits contain a switching system which permits the antenna feed to be switched from CURRENT to VOLTAGE feed. The setting of the ANTENNA FEED CONTROL depends upon the length of the antenna and the frequency of the transmitter.

A MODULATOR UNIT, common to both the I.F. and H.F. transmitters is included in the transmitter assembly. When the transmitter is set on M.C.W., the modulator unit acts as an audio oscillator, producing an 800 cycle note.

The equipment can be controlled and keyed by using either the remote control unit supplied with the TDE transmitter, or the Navy standard four-six wire remote control systems. For remote telephone operation, either the remote control unit supplied, or a Navy Radiophone unit (Navy type 23211 or 23172) may be used.

Legend for Figure 165.

COMMON CONTROLS

INTERMEDIATE FREQUENCY BAND CONTROLS
(Operative when I.F., H.F. switch is set in I.F. position)

HIGH FREQUENCY BAND CONTROLS
(Operative when the I.F., H.F. switch is set in I.F. position)

OPERATION

GENERAL

In these instructions it is assumed that the transmitter has been calibrated, and the dial settings from the various frequencies are correct as indicated. If discrepancies are present, or the transmitter fails to operate properly as indicated by the meters, call a technician.

PRECAUTIONS

The maximum permissible plate current for the final amplifier for the three types of emission, WHEN LOADED TO THE ANTENNA CIRCUIT, is as follows:

Under conditions of non-resonance in the P.A. tank, the product of plate current and plate voltage should not exceed 125 watts.

TUNING THE HIGH FREQUENCY SECTION FOR C.W. EMISSION.

1. Set the following controls and switches in the indicated positions.

3. Set up the FREQUENCY METER on the desired transmitter frequency, and make the necessary patch cord connections between transmitter and frequency meter.

4. Press the START button and adjust FILAMENT rheostat control until the FILAMENT meter indicates 10 volts.

5. Press TEST button on the handrail, and tune the M.O. by adjusting the M.O. TUNING, control C, until a zero beat is obtained in the vicinity of its preliminary setting. Disconnect frequency meter.

6. Place ADJUST-TUNE-OPERATE switch in TUNE position .

7. If MULTIPLIER RANGE, control D, is in the 1.5 to 3.0 mc. position, the MULTIPLIER TUNING, control E, is inoperative. In this condition, the I.A. GRID current should not exceed 0.5 ma. When the MULTIPLIER RANGE, control D, is in ANY OTHER POSITION, adjust MULTIPLIER TUNING, control E, for maximum I.A. GRID current. It should read between 2 and 5 ma.

8. Adjust I.A. TUNING, control G, for maximum P.A. GRID current. It should be between 30 and 50 ma.

9. Adjust P.A. TUNING, control J, for minimum P.A. PLATE current.

10. All the adjustments in the next following step are performed with the TEST button depressed.

12. When the antenna circuit has been tuned to resonance, place the ADJUST-TUNE-OPERATE switch in the OPERATE position, and adjust the PLATE VOLTAGE rheostat to a position where the PLATE VOLTAGE meter indicates 2,000 volts.

14. Repeat step 13 as many times as it is necessary until a P.A. PLATE current of 175 ma. is obtained without overcoupling. (See note on overcoupling on page 283.) If overcoupling exists between power amplifier and antenna circuits, REDUCE the coupling until the condition is remedied, REGARDLESS of whether the indication on the P.A. PLATE current meter is of the maximum value or not.

ADJUSTMENT FOR M.C.W. EMISSION.

1. Repeat the tuning procedure for C.W. emission, and then place the C.W.-M.C.W.-VOICE switch in the M.C.W. position. Adjust the ANTENNA COUPLING, control K, decreasing or increasing as necessary, to obtain a P.A. PLATE CURRENT not in excess of 120 ma. Be sure the antenna circuit is not overcoupled to the power amplifier stage. For each change in ANTENNA COUPLING, repeat step 13.

ADJUSTMENTS FOR VOICE EMISSION.

1. For voice operation, the tuning procedure is the same as for C.W. emission, except the power amplifier stage is not loaded in excess of 110 ma. remember, with this transmitter you reduce the loading of the power amplifier by reducing the ANTENNA COUPLING.

1. Set the following controls and switches in the indicated positions.

2. Set the following lettered controls to the position indicated on the calibration card:

3. Repeat the tuning procedure outlined in steps 3 through 7 for tuning the H.F. section of the transmitter.

4. Adjust P.A. TUNING, control R, for minimum indication on the P.A. PLATE current meter.

5. Increase the ANTENNA COUPLING, control S, to read 15 scale divisions.

6. All the adjustments in the next step are performed with the TEST button depressed.

7. Perform ONLY AS MANY STEPS, a through d, as is necessary to resonate the antenna circuit. Resonance will be indicated by a MAXIMUM antenna current, or an INCREASE in P.A. PLATE current, or both. Do not continue to make adjustments after resonance has been obtained.

699198°-4a-19

8. Place the ADJUST-TUNE-OPERATE switch in the OPERATE position, and adjust the PLATE VOLTAGE rheostat until an indication of 2,000 volts is obtained on the PLATE VOLTMETER.

9. Retune the antenna system for maximum antenna current, then adjust the ANTENNA COUPLING, control S, for a reading of 175 on the P.A. PLATE current meter, or until the antenna current stops increasing as the coupling is increased, whichever occurs first. Do not readjust the P.A. TUNING, Control R, during this final tuning step.

ADJUSTMENT FOR M.C.W. EMISSION.
1. Place the C.W.-M.C.W.-VOICE switch on the M.C.W position. Adjust the ANTENNA COUPLING, CONTROL S, so that the P.A. PLATE current meter does not indicate over 120 ma.

ADJUSTMENT FOR VOICE EMISSION.
1. Place the C.W.-M.C.W.-VOICE switch on the VOICE position. Adjust the ANTENNA COUPLING, control S, until the P.A. PLATE current meter does not indicate over 110 ma.

CONTROL OF THE TRANSMITTER.
1. Control of the transmitter can be given to any

OPERATION WITH REDUCED POWER.
1. The output power of the transmitter can be reduced to about 25 percent of its full rated value by decreasing the coupling between the power amplifier and antenna circuits. In the H.F. sections, this is done by decreasing the setting of ANTENNA COUPLING, control K. In the I.F. section, it is done by reducing the setting of ANTENNA COUPLING, control S.

CHECKS FOR DETERMINING THE PRESENCE OF OVER-COUPLING.

The table on this page will aid you in determining whether or not overcoupling exists between the power amplifier and the plate circuit. Remember that you vary the controls only SLIGHTLY off resonance in making the tests.

THE TBS RADIO TRANSMITTING AND RECEIVING EQUIPMENT

The TBS radio transmitting and receiving equipment is designed to provide short-range communication between surface craft such as task forces or convoys. While in theory the radius of communication of the TBS is limited to approximately the horizon, actual contacts of many times this range are on record. (See chapter 14.) The type of emission may be either VOICE or M.C.W., with 50 watts of power.

Transmitter frequency is determined by a crystal oscillator within a single band of 60 to 80 mc. The NUMBER of usable frequencies is determined by the supply of available crystals that will produce an output frequency within the band.

The frequency marked on the crystal holder is actually the third harmonic of the crystal. The output frequency is four times the crystal frequency, and is obtained by two frequency doubler stages following the oscillator. Each time you wish to change transmitter frequency, it is necessary to exchange the crystal being used with the one of the desired frequency.

The oscillator stage of the receiver is also crystal controlled, so that you must change crystals each time you wish to change the receiver's frequency. Tuning the receiver is done by adjusting the r.f. sections, so that the incoming signal will produce with the oscillator frequency, an intermediate frequency of 5.3 mc.

Control of the set can be exercised either locally or from several designed TBS remote control units. These remote control units have outlets for a handset, a chestset, and a loudspeaker.

Power to operate the TBS is derived directly from motor-generator sets, with appropriate magnetic controllers. The power to drive the motor-generators is obtained from a variety of d.c. and a.c. sources. The chief difference in the various TBS models is in the motor-generator units used.

The transmitter section may be turned on from a remote station, but the receiver must be switched on locally. The power to operate the receiver is taken directly from a 110/120 volt, 60 cycle, single-phase line. By this arrangement, the receiver may be used as a separate unit while the transmitter is not energized.

TRANSMITTER CONTROL PANEL

RECEIVER CONTROLS PANEL

OPERATION OF THE TBS TRANSMITTER

1. Check the following controls to see they are set in the indicated positions:

3. Set all tuning dials in approximately the correct position as indicated by calibration card. Press START button.

4. Adjust OSCILLATOR dial until the PLATE and GRID CURRENT meter drops to minimum. It should indicate about 25 ma. This is just a preliminary setting of the OSCILLATOR dial.

5. Turn METER SWITCH to 1st DOUBLER position. adjust 1st DOUBLER dial until a minimum indication is obtained on PLATE and GRID CURRENT meter. It should be about 35 ma. Make this adjustment CAREFULLY, because the dip may be slight, and can be missed easily.

6. Rotate METER SWITCH TO I_P -1st DOUBLER position. Adjust 2nd DOUBLER dial until a minimum indication is obtained on PLATE and GRID CURRENT meter. It should read about 40 ma.

7. Set METER SWITCH on I_P -PA. Adjust POWER AMPLIFIER dial until a minimum indication is obtained on the PLATE and GRID CURRENT meter. It should read about 70 ma.

8. Place TUNE-OPERATE switch in OPERATE position. The PLATE and GRID CURRENT meter should show close to 115 ma. If the meter indicates a current either above or below this value, call a technician to make the necessary adjustments.

9. Turn METER SWITCH to I_G -PA. Carefully adjust both DOUBLER dials until a MAXIMUM indication is obtained on PLATE and GRID CURRENT meter. Next, detune, the OSCILLATOR slightly by moving the OSCILLATOR dial a few points TOWARD the HIGH end of the dial. The PLATE and GRID CURRENT meter should show about 35 ma.

10. Lock all tuning controls in place. The transmitter is now ready for operation.

OPERATION OF THE TBS RECEIVER

1. Set the following receiver controls (lower row) in the indicated positions:

2. Turn receiver ON and allow it to warm several minutes before tuning. With INPUT METER switch on position three, adjust OSCILLATOR dial slowly until there is a sharp dip of the INPUT METER needle. Then move the OSCILLATOR dial SLIGHTLY to the right of the point where the minimum indication is obtained.

3. Place INPUT METER switch on position numeral. Adjust the 1st and 2nd DOUBLER dials until a maximum reading is indicated on the INPUT METER. These dial settings will be close to the settings of the OSCILLATOR dial.

4. Turn INPUT METER switch to position one, and adjust ANTENNA, LINK, and DETECTOR dials until a maximum is obtained on OUTPUT METER, or until a maximum NOISE is heard in the headset or loud speaker. When frequencies near the lower end of the band are being used, all the tuning dial settings will be nearly the same. At the high end of the band, the antenna, link, and detector dials may vary from the oscillator setting.

5. After tuning is completed, the VOLUME CONTROL is usually advanced to about 6 or 7 depending on the strength of the signal and background noises.

6. Turn the NOISE SUPPRESSOR up until as much as possible of the undesirable background noise is

7. Set the A.V.C. TIME CONSTANT to the position indicated for the condition of the operation described.

8. After final adjustments have been completed, close hinged door and lock in position. If signal strength falls off, check tuning of receiver. If tuning is correct, turn up volume control. With very weak signals, it may be necessary to turn the noise suppressor down.

9. Remember, the receiver can not be turned on or off from a remote station. You must do that manually at the set.

THE TDQ RADIO TRANSMITTING EQUIPMENT

The Navy model, TDQ radio transmitting equipment is a very high frequency transmitter, 115 to 156 mc., specifically designed for voice or M.C.W. communication with aircraft.

A crystal oscillator containing four interchangeable crystals determines the specific frequency being used.

The nominal output power of the transmitter is 45 watts. The modulator unit is capable of voice modulating the carrier wave up to 100 percent. On M.C.W. transmission, modulation up to 85 percent with a 1,000 cycle note is possible. Keying speeds up to 40 words per minute are permissible.

You may operate the transmitter on a 115 volt or a 230 volt, 50/60 cycle line supply. It may also be used with a 440 volt, 50/60 cycle supply by using an

Three separate units are contained in the TDQ cabinet. The radio frequency equipment occupies the top portion, the modulator the middle section, and the power supply the lower portions of the cabinet.

Operation of the transmitter is possible from either a local or any one of several remote stations. The TDQ is intended to be used with the RCK receiver. Both transmitter and receiver can be controlled from any remote unit.

A single vertical dipole antenna is used with the TDQ, and is connected to the transmitter by a coaxial

RADIO FREQUENCY SECTION

POWER SUPPLY SECTION

OPERATION OF THE TDQ TRANSMITTER

GENERAL

1. The frequency of the TDQ transmitter is limited to the frequencies of the harmonics produced by the four crystals. If other frequencies within the 115-156 mc. range are desired, it is necessary to interchange crystals. The door above the crystal selector switch provides access to the crystal heater chamber.

2. Tuning the r.f. sections consists of resonating the oscillator plate circuit to the crystal frequency, the 1st tripler plate circuit to the third harmonic of the crystal frequency, and the 2nd tripler plate circuit to the third harmonic produced by the 1st tripler stage. The power amplifier is tuned to the frequency of the 2nd tripler stage.

1. Set the following controls and switches in the indicated positions.

2. Set the CRYSTAL SWITCH, control A, in the position of the desired frequency.

3. Place TEST KEY in LOCK position.

4. Turn PLATE CURRENT switch, control D, to O.S.C. position.

5. Refer to the calibration card and set O.S.C. TUNING, control B, in the position indicated by the card. Starting from slightly BELOW the correct setting, adjust the control until a minimum indication is obtained on the PLATE CURRENT, meter M2. Then continue to rotate control B toward the HIGH frequency end of the dial, until the PLATE CURRENT meter needle has increased about I/2 a scale division. Lock control B in place.

6. Turn PLATE CURRENT, control D, to "1st T" position, and quickly adjust 1st TRIPLER TUNING, control C, until a minimum indication is obtained on the PLATE CURRENT, meter M2.

7. Turn PLATE CURRENT, control D, to "2nd T," and quickly adjust 2nd TRIPLER TUNING, control E, until a minimum indication is obtained on the PLATE CURRENT, meter M2.

8. Turn PLATE CURRENT control D, to "P.A." position, and quickly adjust P.A. TUNING, control F, until a minimum indication is obtained on the PLATE current, meter M2.

9. With the PLATE CURRENT, control D, in P.A. position, place the TUNE-OPERATE switch in OPERATE position. The plate current should read 100 ma., if the r.f. section is properly tuned.

10. Slowly increase the ANTENNA COUPLING, control G, a few degrees. Readjust control F, until a minimum indication on the PLATE CURRENT, meter M2, is obtained.

11. Continue to increase ANTENNA COUPLING, control G, and if necessary readjust P.A. TUNING, control F, until the PLATE CURRENT meter reads 230 ma. Do NOT increase plate current beyond 230 ma.

12. Check the P.A. GRID CURRENT, meter M1. It should indicate 11 to 15 ma. If it is either too high or too low, call a technician.

13. Press STOP button, and place the REMOTE-LOCAL switch in REMOTE position.

14. The transmitter can be started or stopped, and transmit voice or M.C.W. messages from any remote station.

ROUTING OPERATION OF THE TDQ TRANSMITTER

1. Do NOT operate transmitter-that is, press TEST KEY, TELEGRAPH KEY, or PRESS-TO-TALK microphone button-unless the transmission line is connected to the transmitter.

2. When the transmitter is properly tuned, the TUNE-OPERATE switch will be in OPERATE position, the TEST KEY in NEUTRAL, and the EMERGENCY switch ON.

3. Normally the CRYSTAL HEAT switch will be ON at all times. The HEATER indicator light will be on unless the heater chamber is above 70° C. The thermostat will then open the heater circuit and turn Out the HEATER indicator light. When the

699198 °-X46-20

LOCAL TEST FOR OPERATION OF THE MODULATOR

1. Place REMOTE-LOCAL switch in LOCAL position. Insert microphone plug in MICROPHONE jack, and headset plug in HEADSET jack.

2. Hold the PRESS-TO-TALK microphone button. The CARRIER indicator lamp will come on and stay on as long as the PRESS-TO-TALK button is closed.

3. To hear the incoming signal, provided the TDQ has the necessary receiving equipment installed with it, release the PRESS-TO-TALK button. The incoming message will be received instantly. However, if the transmitter is being used for M.C.W. transmission, a one second delay will occur before the incoming message can be heard.

4. To control the volume of either the OUTGOING or INCOMING signal, adjust HEADSET VOLUME, control H.

THE TBY TRANSMITTER-RECEIVER EQUIPMENTS

The Navy model TBY sets are very high frequency, portable, transmitter-receivers. They are capable of two-way communication by either VOICE or M.C.W. telegraphy on any one of 130 different channels within a frequency range of 28 to 80 mc.

These sets have battery power supplies, and are designed for transportation as a knapsack load. They also can be operated by the man who is carrying them on his back.

Both transmitter and receiver are housed in a lightweight aluminum cabinet to which the battery power supply is strapped. The entire assembly is contained in a canvas carrying case. The case may be partially or fully removed from the transmitter-receiver as is desired for the operation of the set.

The antenna supports are located on the left side of the cabinet. The antenna itself is in 10 sections, fitted together in a "fish-pole" fashion to form a completed unit nine feet long. The length and diameter of each section depends on its position in the completed assembly. The end of each section is color coded to facilitate the proper assembly of the antenna.

Microphone-headphone assemblies consist of an aircraft anti-noise type microphone and a special lightweight headphone. The microphone is equipped with a PRESS-TO-TALK switch, which transfers the transmitter-receiver units from "receive" to "transmit" when pressed. Each transmitter-receiver unit has two jacks, which permit the simultaneous use of two microphone-headphone assemblies.

Only one operator may actually control the equipment at a time. The second operator acts as a monitor during the operation. Control of the equipment may be transferred from one operator to the other at will.

The key, cord, and plug assembly consists of a specially designed key housing in a small aluminum box. In addition to the key, this unit contains a SEND-RECEIVER switch that performs the same function as the press-to-talk switch on the microphone. The whole unit is covered with a rubber cap. This protects the key when the set is operating in rain or in the presence of spray.

The battery pack is strapped to the underside of the transmitter-receiver unit. It is equipped with a receptacle which automatically makes the electrical connection to the transmitter-receiver unit when the battery is installed, thereby facilitating rapid change of batteries. The complete battery unit is encased in a lightweight metal container which protects the battery from becoming defective when set in water or other foreign matter up to a depth of approximately two inches.

THE TBY TRANSMITTER-RECEIVER CONTROLS

OPERATIONS OF THE TBY TRANSMITTER-RECEIVER

The frequency range of this equipment, as previously explained, is 28 to 80 megacycles. Throughout this range, the equipment is calibrated for operation on any one of 130 channels separated from each other by 400 kc. The calibration chart on the top cover of the transmitter-receiver unit gives the dial settings and antenna sections to be used for each of these channels. The channels are numbered from 1 through 130, with No. 1 channel being

If the equipment is to be operated at a fixed location, the operating site selected should be clear and free from obstructing objects such as trees, hills, and the like.

When the equipment is to be operated from a man's back, the tuning procedure for the transmitter differs slightly from the procedure for a fixed position.

PRELIMINARY

1. Remove the antenna sections from their pocket in the side of the canvas case, and assemble the NUMBER of sections indicated in the calibration chart for operation on the desired channel.

2. Remove the combination microphone-headphone assembly and the key, cord, and plug assembly from the pocket at the top of the knapsack. Plug them into the proper receptacles in the front of the panel.

3. Refer to the calibration chart and set the TRANSMITTER BAND and RECEIVER BAND selector switches and both TRANSMITTER and RECEIVER TUNING CONTROLS to the points indicated for the desired CHANNEL. Turn set ON.

4. Turn METER SWITCH to R.F. FILAMENT voltage, and adjust R.F. FILAMENT RHEOSTAT until the meter needle is in the center of the white mark. Next turn the METER SWITCH to AUDIO FILAMENT voltage and adjust AUDIO FILAMENT RHEOSTAT until the meter needle is in the center of the white mark.

1. Adjust the VOLUME control to approximately its mid-position. Then advance the REGENERATION control clockwise from its extreme left hand position until a definite "rushing" or "hissing" sound is heard in the headphone.

2. Set RECEIVER ANTENNA TUNING control to approximately resonance. This is an estimated setting. When the control is in the extreme counterclockwise position, it is set for the high frequency end of the band.

3. Tune in the desired signal by slight readjustment of the RECEIVER TUNING control, if necessary. correct tuning is indicated by the presence of a minimum of hissing noise.

4. Complete the RECEIVER ANTENNA TUNING until a minimum amount of hissing noise is heard in the headset.

5. Make the final adjustment of the REGENERATION control by setting it at a point just ABOVE the point where the hissing noise appears.

TRANSMITTER ADJUSTMENTS

1. Turn METER SWITCH to TRANSMITTER PLATE MA. position. Push press-to-talk button on the microphone, or place the SEND-RECEIVE switch on the key to SEND position.

2. With the SEND-RECEIVE switch in SEND position, adjust TRANSMITTER ANTENNA LOADING control until the meter needle is in the center of the white mark on the meter face. This adjustment should always be made by approaching the proper plate current value by a clockwise rotation of the antenna control from a ZERO setting.

TELEPHONE OPERATION

1. For telephone operation, after the above adjustments have been made, it is only necessary to press the press-to-talk button on the microphone and talk normally into the microphone. The SEND-

TELEGRAPHIC OPERATION

1. For M.C.W. operation of the transmitter, place the SEND-RECEIVE switch in SEND position and operate the key. While M.C.W. operation is being used, a side tone is heard in the headphones making it possible for the operator to hear his own message.

OPERATION WHILE BEING TRANSPORTED ON A MAN'S BACK

1. The operation and tuning of the receiver when the transmitter-receiver unit is being transported on a man's back is exactly the same as it is for operation from a fixed position, since the receiver is not affected by the proximity to the man's body.

2. However, transmitter operation and output frequency are somewhat affected by the nearness of the man's body to the antenna. Therefore, a few slight changes in tuning of the transmitter are necessary.

3. First, tune the transmitter in the normal manner while it is setting in a fixed position. After a normal tuning, ADVANCE the TRANSMITTER ANTENNA LOADING control until the meter needle is about 1/8 inch beyond the white mark.

4. Lift the transmitter to the man's back, and notice the reduction in TRANSMITTER PLATE current. If the needle comes to rest in the center of the white mark, the adjustment is correct. If the needle remains above the white mark, reduce the TRANSMITTER ANTENNA LOADING control until the setting is correct. If the TRANSMITTER PLATE current is less than normal, increase the setting of the TRANSMITTER ANTENNA LOADING.

RECALIBRATION OF TBY TRANSMITTER-RECEIVER

Changing of vacuum tubes, long protracted usage of the set, and even periods of inoperation may cause the

The crystal in the calibrator circuit is of a 5 me. frequency. The transmitter-receiver frequency is checked on some multiple of this frequency-such as 30, 35, or 40 me.-throughout the frequency band. The settings of the tuning controls for the 10 check points are clearly indicated on the calibration chart.

It is a good practice, to insure being on frequency, to make calibration checks each time before tuning, especially if the set has had continued use, or has been subjected to extensive handling. When making a calibration check, always use two or more check points. Don't depend on a single check to insure accuracy.

RECEIVER CALIBRATION CHECK PROCEDURE

1. Turn the CRYSTAL ON-OFF SWITCH to ON. Set RECEIVER TUNING at the points indicated for the check point selected on the calibration chart. Adjust RECEIVER TUNING control, and RECEIVER ANTENNA TUNING control if necessary, to a point where the hissing sound is minimum. The receiver is tuned to the frequency of the crystal.

2. Turn crystal ON and OFF several times. If the hissing sound appears and disappears each time the crystal is turned off and on, you have the receiver tuned to the correct harmonic of the crystal. If the signal does not appear and disappear, adjust tuning control until it does.

3. When the receiver has been tuned sharply to the crystal frequency, record the dial settings. Check these settings against the calibration chart. If calibration of receiver is correct, these settings will be the same.

4. If the dial readings and indicated chart settings are different, record this difference and use it as a

5. If the difference between the actual setting and chart indications is as much as 20 points, take the set to a technician for adjustment.

TRANSMITTER CALIBRATION CHECK PROCEDURE

1. Place the set in operation in the normal procedure, and tune the transmitter to one of the indicated check points.

2. Turn the CRYSTAL ON-OFF SWITCH to ON. Adjust the TRANSMITTER TUNING control until a whistling beat note is heard. Continue to adjust the tuning control until the low pitched beat note just disappears. If the tuning control is correctly set, the beat note will reappear when the tuning control is moved in either direction.

3. While you are making the above adjustment, remain IN ONE POSITION, preferably as far below and to the right of the antenna as possible.

4. When making calibration checks be sure to keep TRANSMITTER PLATE MA. normal at all times.

5. If the settings for the controls indicated on the chart are correct, they should be the same as the dial settings. If the dial setting and chart indications are different, use this difference as a correction factor the same as with the receiver sections. Be sure, if the dial settings are lower than the chart indications, to subtract the differences from the chart indications.

6. If calibration shows chart settings to be considerably in error, take the set to a technician.