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6
SINGLE-PING ECHO-RANGING
If the conning officer requires a range more accurate than his periscope can give, he may order, "QB, get a single-ping range." The sonar operator then aims his projector at the target and shoots out a single burst of supersonic sound called a ping. The time until the echo returns gives a measure of the target's range. There will be a series of small echoes, called reverberations, but the clear note of the main echo from the target can generally be distinguished.
 
Illustration of a ping and echo.

This requires two additional units of equipment, different from those which have been discussed so far.

The Driver sends a pulse of current of supersonic frequency to the projector, which projects a ping into the water. There are two drivers, both located in the forward torpedo room. One is connected to the QB projector; the other is used with either the QC projector (echo-ranging) or the NM projector (echo-sounding to get the depth of water beneath the keel).

The Range Indicator is a giant electric stop-watch which measures the time between the ping and the return of the echo. Its dial is marked off in yards so that the range can be read directly.

 
Photo of driver in torpedo room.
 
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WCA, WCA-1, and WCA-2 Range Indicators

 

Photo of WCA and WCA-1 Range Indicator.

WCA and WCA-1

The black panel containing four screw driver adjustments appears only on WCA and WCA-1 range indicators. Power can be obtained from a generator or from the ship's AC.

 
Photo of WCA-2 Range Indicator.

WCA-2

In WCA-2 the screwdriver adjustments have been replaced by hand switches. There are no generator buttons because this model operates entirely on ship's AC.


Advantages of QB for single-ping echo-ranging

Although either QB or QC can be used to get a single-ping range, QB is better for several reasons:

1. You are more certain of getting a good range on a single ping. Although both send out about the same strength of sound, QB can pick up a weaker echo.

2. You do not have to be so exact in setting the tuning dial when using QB. With QC, it is necessary to tune to an exact frequency.

3. If you have been using JK for listening, before you can use QC, it is necessary to turn the input switch to QC and train the QC bug halfway around the bearing circle. With QB you are ready to ping instantly.

QC must be used when the target bears between 250 degrees and 290 degrees relative. At these bearings the QB projector is blanked out by the JK/QC projector, which is then between it and the target.

 
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How to set the controls for a single-ping range on QB

Photo of WCA or WCA-1 indicator showing controls.
1-Visual-audible switch on Manual Keying.
2-Red Light switch on QB System.
3-QB Driver Power Supply on Ship's A.C.
4-QB Amplifier power supply on Ship's A.C.
5-Indicator power supply on Ship's A.C.

Photo of WCA-2 indicator showing controls.
1-Indicator power supply on.
2-Visual-Audible switch on manual keying.
3-Red Light switch on QB system.
4-QB driver power supply on.
5-QB amplifier power supply on.
6-Push equipment start button.

On the QB receiver-amplifier

1. Use the frequency on which you have been listening, which should be about 28 kc, because you have raised the tuning to narrow the target.

2. Be sure filters are on BROAD-FLAT.

3. Be sure the driver-power switch is on HIGH.

 
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How to set the controls for a single-ping range on QC

Photo of WCA or WCA-1 indicator showing controls.
1-Push generator start button.
2-Visual-Audible switch on manual keying.
3-Red Light switch on WA system.
4-WA driver light on.
5-Indicator power supply on.
6-WA Amplifier power supply on.
7-Sounding light out.
8-Push equipment start button.

Photo of WCA-2 indicator showing controls.
1-Indicator power supply on.
2-Visual-Audible switch on manual keying.
3-Red Light switch on QC system.
4-QC driver light on.
5-QC amplifier power supply on.
6-Sounding light out.
7-Push equipment start button.

On the QC receiver-amplifier

1. Turn input switch to QC. Train the projector through half a circle so that the QC bug is on the bearing of the target.

2. Tune exactly to the frequency written above the tuning dial. Very accurate tuning is extremely important.

3. Be sure filters are on BROAD-FLAT.

 
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How to get a single-ping range
by the audible method
Illustration showing target bearing.
  1. Train the bug 2 degrees toward, the target's bow from the bearing where the sound is loudest. Turn the gain down to protect your ears.
 
Illustration showing audible selected.
  2. Just before the white light slit reaches zero, move the switch to AUDIBLE, keeping one hand on this switch.
 
Illustration showing gain selected.
  3. When the slit has passed 300 yards, return the gain to its former level in order to get a louder echo.
 
Illustration showing revolving slit and echo on headphones.
  4. Keep your eyes on the revolving slit and listen intently for the echo. Disregard the rolling reverberations, and concentrate on catching the clear note of the returning echo from the target. At the instant it comes, note the reading on the scale. This is the range.
 
Illustration showing manual keying selected.
  5. When the slit reaches 4000 yards, return the switch to MANUAL KEYING.
 
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When and how to use the visual method

Sometimes when your submarine is within 1500 yards of the target, the visual method may be used instead of the audible method. This requires two changes:

1. Instead of setting the switch at AUDIBLE, above it to VISUAL.

2. When the light slit arrives at zero, an arc of red light will flash, indicating that the ping is going out. Following this there will usually be a series of little red flashes caused by the reverberations. Then a good solid red flash will come at the same time that you hear the target echo. Read the range at the trailing edge of this flash.

This visual method involves two serious dangers. First, if the gain on the receiver-amplifier is set too high, you will get a confusing series of red flashes all over the dial from the reverberations. Second, to flash the red light requires more current than to produce an echo in the headphones; so you are likely to get no flash at all from a weak echo.

Why submarines do not echo-range continuously

Since the speed of surface escort ships produces a noise level too high for efficient listening, they depend heavily on echo-ranging to detect submarines. In fact, surface escorts echo-range continuously. But submarines hardly ever echo-range, because a submarine has to keep its location secret from the enemy. Continuous pinging would be a dead giveaway.

When the submarine conning officer needs a sonar range, he allows the operator only a single ping. For the submarine's purpose a successful single ping range is sufficient -- and it's fairly safe.

 
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