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5
SUPERSONIC LISTENING

The WCA system of sonar gear is used for supersonic listening, and also for echo-ranging and depth-sounding. It consists of three main divisions: QB, JK/QC, and NM. In this chapter we shall be concerned with the use of QB and JK/QC for supersonic listening. However, to keep things straight, we shall start with a brief description of the whole WCA system.

 

Projectors

The QB projector is a spherical hydrophone mounted on the lower end of the starboard training shaft. One face contains rochelle salt crystals, which change shape when a sound wave strikes this face of the projector. The other side is empty.

The JK/QC combination projector is mounted portside. The JK face is just like QB. The QC face contains small nickel tubes, which change size when a sound wave strikes this face. (The NM projector, mounted on the hull centerline in the forward trim tank, is used only for echo sounding.)

Change in shape of the salt crystals (QB, JK) or in the size of the metal tubes (QC, NM) generates a small electric current in connecting cables.

Receiver-amplifiers

In the receiver-amplifier, the small electric current is strengthened and changed so that it is heard as sound in the phones or speaker. Two receiver-amplifiers, QB and JK/QC, are in the conning tower. There is also a receiver-amplifier in the forward torpedo room for emergency use with either system.

Remote-control units

In the conning tower are two remote control units, one for the QB, the other for the JK/QC projector. These operate the training motors, and also show the direction in which each projector is trained.

 
Photo of sound head.

Hoist-lower-train mechanisms

Both shafts are equipped with hydraulic mechanisms for raising and lowering the projectors. Training motors and reduction gears turn the shafts and projectors. Power is supplied by two motor generators. All of these units are in the forward torpedo room.

Other parts

The remaining parts of the WCA are concerned with echo-ranging or depth sounding. For echo-ranging there is a QB driver and a QC driver in the forward torpedo room, and a range indicator in the conning tower. For echo-sounding, there is a depth indicator in the control room. (The QC driver is also used for NM in depth sounding.)

 
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In the conning tower

The photograph below shows a WCA stack, in which five units are grouped for efficient supersonic operation. There are separate remote-control units for the starboard (QB) and port (JK/QC) projectors, each with its receiver-amplifier. During routine search only one type of supersonic gear is manned. But when a contact is reported, QB is taken over by the sonar operator whose battle station is at the stack, and a second operator mans JK/QC. Normally during an attack, QB tracks the target, while JK searches for other ships. The range indicator is not used for listening.

Photo of WCA installation in the conning tower.
QB Remote Control Unit
Range Indicator
JK/QC Remote Control Unit
QB Receiver
JK/QC Receiver.

 
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In the forward torpedo room

The spare receiver-amplifier and training control is shown on left.
General view looking aft showing training shafts for both projectors is shown on right.

The photographs above give a general picture of the WCA gear in the forward torpedo room, looking aft, with projectors raised. These are lowered by a torpedoman, operating the hoist-lower mechanisms. If for any reason, the conning tower has to be abandoned, supersonic listening can still be carried on from the spare units in this room. These include a receiver-amplifier, which can be connected to either JK or QB, and a training control for turning either shaft. Relative bearings can be read directly from the scale and pointer on each hoist-train shaft. True bearings cannot be read.

Limit switches prevent training either shaft more than 2 1/4 turns, as a protection to the cables. If you train far enough to hit one of these switches, the training motor automatically stops. You must then train back one full turn. Where slip rings have been installed, the training shaft can be turned continuously in either direction without damage to the cables - eliminating the need for limit switches.

 
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This is how the

Block diagram of WCA amplifier.
Radio-Frequency Amplifier Stage -> First Mixer (gets input from First Oscillator) -> Broad Intermediate-Freq Amplifer Stage and Shart Intermediate-Frequency Amplifier Stage -> Second Mixer (gets input from Second Oscillator) -> Audio-Frequency Amplifier Stage -> Flat Filter, and Band Filter, and Peak Filter -> Audio Frequency Amplifier Stage/Output Amplifier Stage/Transformer/Range Indicator and Output Amplifier Stage/Transformer/Loud Speaker and Headphones.

 
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receiver-amplifier works

First oscillator produces a current whose frequency is 60 kc higher than that of the incoming current. For example, with an incoming current mainly of 17 kc, this oscillator would develop 77 kc (17 plus 60).   Radio-frequency-amplifier stage increases the strength of the current coming from the projector.

First mixer combines these two currents to get a frequency that is mainly 60 kc (77 minus 17). The frequency obtained by mixing is always equal to the difference between the frequencies that are mixed.

 
BROAD Intermediate-frequency-amplifier stage strengthens a broad band of frequencies centered around 60 kc.   SHARP lntermediate-frequency-amplifier stage strengthens a narrow band of frequencies centered around 60 kc.
 
Second oscillator, as normally set, produces a current whose frequency is 60,800 cycles.   Second mixer combines this 60,800-cycle current with the amplified 60,000-cycle (60 kc) current to get a frequency that is mainly 800 cycles (60,800 minus 60,000).

Audio frequency amplifier stage makes the current from the second mixer stronger.

 
Flat filter passes frequencies from 200 to 3000 cycles.

Audio-frequency-amplifier stage makes the filtered current still stronger.

Output - amplifier stage makes this current strong enough to operate the red light on the range indicator.

Transformer changes the amplified current so that the range indicator can handle it.

Range indicator. Here the current makes a red neon light flash. This indicator is not used for listening.

  Band filter passes frequencies from 600 to 1000 cycles.

Peak filter passes practically only 800 cycles.

Output-amplifier stage makes the filtered current strong enough for the head phones or loudspeaker.

Transformer changes this amplified current so that the headphones or loudspeaker can handle it. Loudspeaker changes the electrical current into sound.

Headphones change the electrical current into sound.

 
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These are the steps to take

Photo of amplifier and training remote.
WCA-2 Remote Control Unit and Receiver Amplifier
1-Check to see that the projector has been lowered-Red light on.
2-Push Start button.
3-Turn dial lights on.
4-Move bearing repeater switch to On. With WCA and WCA-1 move it to Ship's AC.
5-Move sensitivity to Receiver.
6-Tune to 17 KC.
7-Driver power on HIGH.

Heterodyne switch. When this switch is off, the second oscillator does not work. Some times propeller beats can be heard with it off. But almost always you should operate with it ON.   Output limiter cuts off part of the sound. Once in a while, when background noise is very high, you may use it. But to avoid losing the target, you will almost always keep it OFF.
 
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in starting WCA listening gear

Photo of WCA amplifier.
8-Move line switch to On.
9-Leave hetrodyne switch on.
10-Turn gain to zero.
11-Turn add decibels to zero.
12-Set gain so that output level meter reads zero.
13-Turn add decibels to 30.
14-Set beat frequency to 800.
15-Turn band width to Broad.
16-Turn audio filter to Flat.
17-Leave output limiter off.
18-Plug phones into jack.

Audio-output-level meter shows the strength of the electric current going to the head phones or loudspeaker.

Add-decibels switch protects this meter from breaking. Always keep it set at 30, except when determining the proper setting for the gain control.

Beat-frequency control. The radio technician uses this control when he adjusts the gear. But for listening, it must always be set at the red 800. Otherwise the target may be lost when the PEAK filter is being used.

Driver-power switch should be left on HIGH. It is set at LOW only when the

  radioman uses the echo-ranging gear to send underwater signals in code to another vessel.

Gain control, when turned clockwise, increases the volume of sound. There is an other gain control on the remote-control unit, labeled "Sensitivity." If you wish to regulate gain from the remote-control unit, move the sensitivity switch to REMOTE CONTROL.

Tuning dial tunes the receiver to whatever frequency is desired. At the same time it automatically adjusts the first oscillator to send whatever frequency is needed to produce 60 kc in the first mixer.

 
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WCA search procedures

When you take over the watch on the WCA stack, check all controls. If necessary, retune to 17 kc. Start with...

 

Rapid search

Swing the remote-control lever so that the bug passes through 000 degrees and continues down the other side to 180 degrees. Then reverse the lever until the bug makes a complete circle to 180 degrees. If you hear no suspicious sounds, shift to

 
Illustration of rapid search.
Progressive search

Reversing direction, sweep 60 degrees forward, then 30 degrees back, 60 degrees forward, 30 degrees back - until you have crossed the bow. Then train quickly down the opposite side to 180 degrees. Again reverse direction and sweep 60 degrees forward, 30 degrees back, 60 degrees forward, 30 degrees back - until you have crossed the bow. Then train quickly down the opposite side to 180 degrees. This completes one full double-cycle (720 degrees).

Illustration showing progressive search.

 
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Frequency search

Every fifteen minutes during a sonar watch, you make a frequency search to try to pick up enemy pinging. This is the sequence for a frequency search:

20 kc - one complete double cycle of progressive search.
23 kc - one complete double cycle of progressive search.
26 kc - one complete double cycle of progressive search.
29 kc - one complete double cycle of progressive search.
32 kc - one complete double cycle of progressive search.
14 kc - one complete double cycle of progressive search.

Then return to 17 kc and continue with the normal search plan.

Rate of sweep

In searching, the proper rate of sweep is somewhat less than the maximum obtained when the remote-control lever is swung all the way over. The position of the lever to get the proper rate has to be determined by experience, since the speed steps vary on different remote-control units.

Reporting enemy echo-ranging

Sometimes a ship's pinging can be picked up before you can hear its screws. Any ship that is pinging is out searching for submarines. Merchant vessels are not equipped for echo-ranging.

So-if you hear pinging report it at once. For example "QB, contact, echo-ranging bearing one one ze-ro." Set your tuning dial to make the pinging come in loud and clear. Estimate the time between pings and report whether the ship is using long scale or short-scale pinging.

Also notice carefully whether you hear the pinging without interruption. If it comes in for a few pings and disappears for a minute or more, comes in again and disappears - the ship is probably still searching. But if it comes in continuously or with only brief interruptions, the ship has probably picked you up as a contact and is likely to attack. This is important information and should be reported immediately.

 
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Contact !

Maybe your whole watch will be spent in just routine searching. But at any moment you may pick up enemy propellers. Then you must quickly do six things:

1. Immediately report the approximate relative bearing of the contact: "QB, contact, bearing thuh-ree ze-ro ze-ro." Even if this bearing is incorrect by 20 degrees or 30 degrees, it lets the conning officer know the general direction of the target. If you are not sure your contact is a ship, report it anyway: "QB, doubtful contact, bearing thuh-ree ze-ro ze-ro."

2. Reset your amplifier controls to get better bearings. Turn the gain down to the lowest possible setting on which the target can be clearly heard.

Turn the tuning control to the highest frequency on which the target can be clearly heard.

Shift the audio switch to BAND. If you cannot hear the target, return the switch to FLAT.

3. Keep sweeping across the targetall the time you are making these adjustments. Keep reading accurate bearings and reporting them. Report relative bearings, but note the true bearing at the same time. If your submarine changes course, you can maintain contact with the target by following its true bearing during the turn. Get in the habit of noticing the true bearing every time you read and report a relative bearing.

4. Identify the target. Describe its screws as heavy or light, slow or medium or fast. Tell what type of ship it is. "QB, bearing thuh-ree thuh-ree fo-wer. Heavy, slow screws. Sounds like a tanker."

5. Take a turn count and report the number of rpm. Whenever the target's speed changes, report that fact at once: "QB, bearing thuh-ree fo-wer niner. Heavy screws speeding up." Then get the new turn count and report the rpm.

6. Try new filter settings from time to time. If you are on BROAD-BAND, shift to BROAD-PEAK and then to SHARP-PEAK. Be ready to shift back instantly if on the new setting you lose the target. When you change filters, you may have to change your gain setting. But keep the gain as low as possible at all times.

 
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Using tuning, gain, and filters to narrow the target

These three controls must work as a team. They must be handled with skill and with a complete understanding of the way they work together.

Tuning high. As the frequency of a sound increases, a hydrophone becomes more and more directional. That is, it picks up sounds over a narrower arc. So it is good practice to take the bearings of a target with the tuning dial set high. Remember, however, that the attenuation is greater at higher frequencies. So if you turn the tuning knob too far, you may not be able to hear the target at all. But always track a target at the highest frequency on which it can be heard.

Gain low. After contact, keep your gain as low as possible. This will make the target's screws stand out from the background noise. Also, because low gain narrows the arc over which you hear the target sounds, you will get better bearings.

Filters help by cutting out most of the background noise, allowing mainly the screw sounds to come through. Sweeping a narrower arc of noise gives more accurate bearings. Below is the order in which you are most likely to use these filters.

Broad and Flat selected.   Because this combination gives a wide listening arc, it is good for searching, but poor for getting bearings.
Broad and Band selected.   Shift to BAND as soon as you can after contact. It gives better bearings.
Broad and Peak selected.   PEAK narrows the arc considerably. It gives even better bearings.
Sharp and Peak selected.   This is the best combination of all. Reach it, if possible, during an approach.
Band With and Audio labels.  
 
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Accurate and continuous bearings

Accurate bearings must be continuously supplied to the conning officer. With some experience, you will learn to get accurate bearings if you follow the proper procedure.

Keep crossing the target completely. Sweep all the way through the arc of propeller noise. Continue until it dies out completely. Then reverse direction and sweep through until it dies out on the other side.

Read when sweeping from bow through stern. As quickly as possible determine which way the target is moving. Then read the bearing on the sweep that goes from the target's bow to the target's stern.

Read the bearing at maximum loudness. Usually you can determine easily a point of maximum loudness. This is the bearing. If the sound is of equal loudness over a wide are, adjust tuning, gain, and filters to narrow it enough to give a distinct maximum.

Securing WCA gear

When your submarine surfaces, you will continue searching. While it is running at a slow speed, you will be able to listen efficiently. But at higher speeds the noise becomes so great that you will have to report to the conning officer: "QB, listening conditions poor." Probably you will then be ordered to secure the gear. Here is the way to secure:

1. Bring the bug either to 000 degrees or 180 degrees, whichever is required by the cable arrangement on your ship. (Ask the radio technician.)

2. Unplug the headphones and hang them up carefully.

3. Push the STOP button on the remote-control unit; the training-motor generator light will go out.

4. Turn the line switch on the receiver-amplifier OFF.

5. The conning officer will order a torpedoman in the forward torpedo room to raise the projectors. Watch the green light in the upper right-hand corner of the remote-control unit. When it glows, you know that the projector has been raised.

 
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