Minelab F1A4 Mine Detector Operations Manual

4.1 Shaft Assembly (see Figure 4)

a. Remove the armrest from the carry bag.

b. Remove the main shaft (including handle) and lower shaft (including coil) from the carry bag.

c. The two shaft assemblies are interconnected by the coil cable that runs through the inside of these hollow components.

d. Ensure the coil cable is fully within the cable groove in the lower shaft. Release the lower camlock lever on the bottom end of the main shaft, position and slide the small end of the lower shaft inside the main shaft to the desired length and clamp these two components together by closing the lower camlock lever.

e. Before attaching the armrest, decide how the Control Box is to be positioned. Release the upper camlock lever at the top end of the main shaft, position the selected grommet on the coil cable into the keyway in the upper camlock, place the end of the armrest inside the main shaft and clamp these two components together by closing the upper camlock lever.

NOTE: It is not necessary to pull the cable through the top of the main shaft if the control box is to be connected to the handle. However, if the cable is pulled through, twisting the coiled section of the cable to "tighten" the coil will make reinsertion of the cable easier.

To repack the detector in its carry bag, pack the components in the following sequence: Folded main and lower shaft, Control Box, Armrest.

Figure 4 - The F1A4 Shaft Assembly: Shows the connection points between the main shaft and the lower shaft, highlighting the coil cable routing and the camlock levers used for adjustment.

4.2 Control Box (see Figure 5)

The Control Box can be positioned in one of three locations:

• It can be placed in its control box bag which is attached to the operator's waist via two belt loops.
• When the webbing strap is used, the control box bag can be worn over the operator's shoulder, or it can hang around the operator's neck.
• It can be attached to the main shaft via a locking bracket located beneath the handle.

a. If the control box bag is to be used to carry the Control Box either worn on the belt or as a shoulder pack, position the grommet (located between the two curled sections of the coil cable) into the keyway beneath the camlock at the top end of the upper shaft. The plug end of the coil cable is then connected to the socket marked Coil on the Control Panel.

b. If the Control Box is to hang beneath the handle on the main shaft, the mounting block on the Control Box is pushed into the locking bracket immediately beneath the handle. Rectangular lugs on the mounting block snap into rectangular holes on the sides of the locking bracket to hold the Control Box loosely in position. To lock the bracket, turn the locking pin fully clockwise until it locks in position. The plug end of the coil cable is then connected to the socket marked Coil on the Control Panel.

c. To remove the Control Box when it is attached to the underside of the handle it is necessary to disconnect the coil cable, and then turn the locking pin counter-clockwise to release the Control Box.

Figure 5 - Control Box Configurations: Displays three ways the control box can be attached: in its bag (worn on a belt or shoulder strap) or mounted directly onto the main shaft beneath the handle.

4.3 Armrest (see Figure 6)

To assemble the armrest:

a. Insert the sharp end of the arm strap through one of the slots at the base of the armrest, then through the slots at the top of the wings of the armrest. When the operator's arm is in the armrest, the protruding part of the "Velcro" strap should be fixed to make a firm fit.

b. Decide whether the Control Box is to be attached to the handle or housed in the control box bag, as this will determine what length of coil should protrude from the main shaft.

c. If the Control Box is to be attached to the shaft, position the cable grommet closest to the plug end of the coil cable into the keyway beneath the camlock at the top end of the upper shaft. (Surplus coil cable can be stored inside the hollow main shaft.)

d. Alternatively, if the Control Box is to be carried in its shoulder pack, position the grommet located between the two curled sections of the coil cable into the keyway beneath the camlock at the top end of the main shaft.

e. When the appropriate grommet is positioned in the keyway, push the end of the armrest assembly into the camlock on the top of the main shaft and clamp using the upper camlock lever.

NOTE: It is not necessary to pull the cable through the top of the main shaft if the control box is to be connected to the handle. However, if the cable is pulled through, twisting the coiled section of the cable to "tighten" the coil will make reinsertion of the cable easier. This technique simplifies shaft reassembly.

Figure 6 - Armrest Configurations: Shows how the arm strap is attached to the armrest and how the armrest assembly connects to the main shaft, showing different cable routing options based on control box placement.

4.4 Battery Pack (see Figure 7)

The F1A4 can be powered by one of two battery packs.

NOTE: Before connecting or disconnecting either battery pack ensure that the unit is switched Off on the Control Panel.

4.5 Comfort Adjustments (see Figure 8)

a. Releasing the upper camlock lever at the top end of the main shaft permits up to 50 mm adjustment of the position of the armrest assembly, relative to the handle position.

b. Releasing the handle camlock lever at the base of the handle allows the handgrip to be repositioned along the length of the main shaft.

c. Releasing the lower camlock lever at the bottom end of the main shaft enables the effective length of the lower shaft to be altered.

d. The hand strap can be changed from right to left-handed by unlacing the handstrap and re-inserting the strap from the other side.

e. The coil angle can be adjusted without adjusting the clamping nut.

CAUTION: Ensure the clamping nut is not over tightened.

Figure 8 - Comfort Adjustments: Points out the adjustable parts of the detector: the armrest position, the handgrip position, the lower shaft length, and the coil angle.

5.1 Control Panel Description (see Figure 9)

All controls are located on the Control Panel.

Figure 9 - The F1A4 Control Panel: A diagram of the control panel, labeling the Off/Search/Balance switch, Noise Cancel button, Audio Reset button, and the Battery Low indicator LED.

• Off / Search / Balance Switch: This three-position switch located near the centre of the Control Panel provides the ability to switch the unit On and Off. Normal detection operations are performed whilst in the Search position. The detector is On when it is switched to either Search or Balance:
  • Search: Using the detector with the switch set to Search means that the setting to cancel ground noise remains fixed. Changing ground conditions may require the detector to be balanced occasionally to cancel any ground noise.
  • Balance: In this spring-loaded position, ground noises can be cancelled out.
• Battery Low: This Red LED flashes and the detector emits a loud oscillating tone when the charge in the batteries drops to a predefined, low level. If the F1A4 is operated while the LED is flashing and the oscillating tone can be heard, the unit may become unstable.
• Noise Cancel: Noise Cancel negates the effects of electro-magnetic interference. Installations such as local television stations, radar transmitters and electrical power cables emit signals that can interfere with the detector. Performing a Noise Cancel procedure forces the detector to reset itself so as to minimise the effects of any interference.
• Audio Reset: The Audio Reset procedure resets the threshold level of the background tone heard from the internal speaker or operator's earset. The best sound level for detecting mines and other ordnance is a faint constant tone, just above no sound at all. Using Audio Reset achieves this ideal setting, but it is possible for the level to drift. In this instance, an Audio Reset procedure should be performed.

WARNING: The detector must always be left in Search when actually searching for mines. It is possible that the signal you are attempting to balance out is that of a small or distant target.

CAUTION: When the detector is emitting a repetitive warble without the coil being moved it is necessary to perform a Noise Cancel procedure. The detector will emit random sounds when operated in close proximity to electrical storms, arc welders and other electrical equipment.

WARNING: The detector must not be used to detect mines and other ordnance while the battery level is low.

5.2 Detector Settings

WARNING: Operators should be aware of other electronic equipment being used in the immediate locality that may affect the operation of the detector.

To initialise the detector in a new area, switch the detector from Off to Search. The detector takes 6 seconds to run through a set-up routine, and during this time 3 long "beeps" with a slowly rising pitch can be heard. Once the set-up routine has completed, Noise Cancel, Audio Reset and Ground Balance procedures should be performed as required. Test the detector with the Test-Piece (refer Paragraph 5.4).

To restart the detector in the same operating area, switch the unit from Off to Search. The detector will take 6 seconds to turn on, and during this time 3 long "beeps" with a slowly rising pitch can be heard. The detector is now set with the same settings that were previously used, that is, the same Audio Reset, Noise Cancel and Balance that applied when the unit was last turned Off. Test the detector with the Test-Piece (refer Paragraph 5.4).

Leave the detector in Search and proceed according to your established Standing Operating Procedures for de-mining.

5.3 Detector Sounds

WARNING: The threshold tone is a safety tone and must be present to ensure correct operation of the detector. If there is a persistent change in this tone, the detector should be tested with the test piece before further use of the detector. (see Section 5.4 for further information on testing the detector.)

• Threshold Tone: is the background tone produced by the detector. The loudness of the threshold is set by the in-built microprocessor. When the detector is turned On or after completing the Audio Reset procedure, the threshold tone should be just audible. The volume of the threshold tone will seldom vary from the level set by the microprocessor. If it does vary and is too loud or too soft, repeat the Audio Reset procedure.
• Target Sound: is an abrupt variation of the audio volume and pitch. The pitch of the tone will vary depending on the metal composition and size of the target. (See Figure 11)
• Ground Noise: is an irregular broad noise that is difficult or impossible to pinpoint when moving the coil over the ground.

If ground noise is affecting the operator's performance, rebalance the detector as described in the Ground Balance procedure.

Figure 11 - Pitch varies as the Coil passes over a target: A conceptual diagram showing how the audio pitch of the detector's signal changes as the coil moves over a target, indicating different metal types or sizes.

WARNING: Target sounds will vary. Different target sounds in the same area may indicate multiple targets. All target sounds must be considered dangerous.

5.4 Testing Procedure / Using the Test Piece

The F1A4 test piece is used to ensure that when the following test is performed, operators can have full confidence that the detector is working to its optimum performance. It should also be noted that under ideal conditions (detector correctly noise cancelled and ground balanced within a quiet background) the test piece will register a clear signal from a greater distance from the centre of the coil.

CAUTION: Follow established standing operating procedures at all times, and use the supplied test piece to confirm that the detector registers a correct signal before and after every use. An area that has just been checked with the F1A4 detector should not be considered safe until the detector has been rechecked with the test piece.

a. Ensure that the detector is emitting the correct threshold tone. If in doubt, perform Noise Cancel or Audio Reset procedure.

b. Make sure your hands and wrists are free of any metallic objects.

c. Place the test piece with the end with the hole lightly against the centre of the bottom of the coil.

d. Confirm that a distinct signal is registered as the test piece is moved in the directions shown in Figure 12.

Figure 12 - Using the Test Piece: Shows the test piece being placed against the bottom of the coil and moved in various directions to confirm the detector's response.

5.5 Sweeping the Coil

a. While sweeping the coil it is important to keep it parallel to and at a constant height from the ground at all times (see Figure 13).

CAUTION: Be aware of any tendency to raise the coil at the ends of each sweep as this will reduce your detection depth.

b. Each sweep of the coil should overlap the area covered by the previous sweep to ensure full coverage of the area being searched.

Figure 13 - Sweeping the Coil: Illustrates the correct technique for sweeping the detector coil, emphasizing keeping it parallel to and at a constant height above the ground.

5.6 Pinpointing the Position of a Small Target

a. When a possible "target" has been located continue to sweep the coil over the location, but reduce the size of the sweeps to more accurately determine the position of the target.

b. To further pinpoint the location, sweep the coil across the ground and advance forward towards the target with a half-coil diameter overlap on each sweep. Notice when the target signal is first heard - this determines the edge of the target area.

c. Advance forward another sweep distance and approach the coil from each side. Notice when the target signal is first heard - this will indicate the side boundaries of the target area. (See Figure 14.)

Figure 14 - Pinpointing a Small Target using Edge Detection: A diagram showing how to narrow down the location of a small target by making progressively smaller sweeps and noting where the signal is first detected at the edges.

5.7 Pinpointing Large or Multiple Targets

If you have a large target or multiple targets it may be difficult to define using the crossing method defined in section 5.6. It is therefore recommended that the following procedure be used to define large or multiple targets.

a. Pass the coil over the target at increasing heights until you get an indication of the main centre (or centres) of metallic mass (see Figure 15).

b. At normal search height, move the coil from outside the detection zone directly towards the centre of the mass, and note where a clear detection signal is heard.

c. Repeat this process at small intervals around the whole target to provide an outline of the shape of the target (see Figure 16).

Figure 15 - Passing the Coil at increasing height: Demonstrates how to determine the approximate center of a large or multiple target by sweeping the coil at increasing heights above the ground.

Figure 16 - Determining the Outline of the Target: Shows a method of tracing the perimeter of a large target by sweeping the coil from different directions at normal search height and noting where the signal is detected.

d. Note if the pitch rises or falls at each interval around the target. If the pitch sound is different it may indicate multiple targets, such as AP Mines or booby traps (see Figure 17).

Figure 17 - Checking the Pitch around the target: Illustrates how varying the audio pitch around a detected target can help identify if it is a single object or multiple, potentially dangerous, targets.

5.8 Operating Multiple Detectors in Close Proximity

When two or more F1A4 detectors are operating in close proximity it is necessary to automatically tune each unit via the Noise Cancel procedure to set the operating frequencies so that the F1A4 detectors do not interfere with each other. To set up multiple detectors it is necessary to adhere to the following procedure:

a. Turn "Detector 1" On, and switch to Search. Wait for the end of the start-up tone. Perform a Noise Cancel procedure if required.

b. With "Detector 1" operational, position "Detector 2" two metres away and turn it On. Wait for the start-up tones and then perform a Noise Cancel procedure to automatically tune the unit. Wait for 70 seconds and the four "beeps".

c. With "Detector 1" and "Detector 2" both operational, position "Detector 3" two metres away and turn it On. Wait for the start-up tones and then perform a Noise Cancel procedure to automatically tune the unit. Wait 70 seconds and the four "beeps".

d. Continue the above procedure if more than three detectors are to be used in close proximity. The recommended minimum operating distance between units is three metres, but if interference does result it will be necessary to limit the number of detectors in use or increase the distance between units.

6.1 Operator Repairs