Metal Detector  (630-3003)         Operation          Faxback Doc. # 6275

The steps in this section explain each control on the control housing and
handle, and how to use your metal detector.  Take a moment to become
familiar with the position and use of the controls before using the metal


The view meter is located at the top of the control housing and measures
battery power, determines the quality of hidden metal, and helps you tune
the detector.

Turning On the Detector

Hold the detector in a position comfortable for you, then turn it on by
rotating VOLUME two-thirds clockwise.  Set TEST to NOR to detect.

Adjusting the Controls in the Field

The tuning skills you will learn while preparing the detector will be put
to good use during your actual search.  You will know how each control
works so you can fine-tune the detector quickly.

If you wish to test the accuracy of your tuning at your current location
in the field, take a few samples of different kinds of metal with you.
Note that some metals, when left exposed to the elements, become
corroded; so, it is always wise to carry along a piece of corroded metal.


Setting TUNE

The Radio Shack VLF Discriminator Metal Detector distinguishes between
ferrous and non-ferrous metals.  When the detector senses a metallic
object, one of two reactions occurs - the sound and meter reading
increase or decrease.  The result depends upon the type of metallic
material, ferrous or non-ferrous.  Ferrous metals contain iron.  Gold
silver, copper, platinum, aluminum, lead, zinc, etc. are examples of
non-ferrous metals.

TUNE fine-tunes the balance between the detector's receiver and
transmitter circuitry.

Follow these steps to set TUNE.

1.  Rotate VOLUME two-thirds clockwise.

2.  Set MODE to VLF.

3.  Set TEST to NOR.

4.  Set the remaining controls to mid-range.

5.  Hold the search coil up in the air, press and hold down Auto-Tune,
    and slowly turn TUNE.  The pointer swings back and forth and the
    detector sounds a tone.  Turn TUNE until the pointer rests at or
    near the center.  Release Auto-Tune.

Note:  Press Auto-Tune during operation to automatically return the
       pointer to the center.

Setting MODE

Set MODE to VLF when you use GROUND (See "Setting GROUND).  Set MODE to
TR1 or TR2 when you use DISCRIMINATOR (See "Setting DISCRIMINATOR)".

Using GROUND helps tune out false signals from mineralized soil.
DISCRIMINATOR distinguishes between NON-FERROUS and FERROUS objects.


To adjust the search coil's ability to detect objects at different
depths in the soil, rotate SENSITIVITY from MIN to MAX.  For maximum
performance, set SENSITIVITY as high as possible.  If the detector
makes a "Chattering noise, decrease SENSITIVITY until the "Chatter"

Setting GROUND

GROUND tunes out false signals from mineralized soil.

Follow these steps to set GROUND.

1.  Set MODE to VLF and lower the search coil to 1/2- to 2 - inches above
    the ground.

2.  If the pointer swings to the left, turn GROUND to the right.

3.  Raise the search coil and press Auto-Tune.  The pointer returns to
    the center.

4.  Repeat Steps 1-3 until there is a very small variation in the meter
    reading each time you lower the search coil to the ground.


  Setting GROUND takes a little time, but is critical for accurate

  After you set GROUND, do not reset it until you use the detector at
  a different site.


DISCRIMINATOR determines whether the hidden metal is NON-FERROUS or

Before you set DISCRIMINATOR, you must set MODE.  Set MODE to TR1 to
detect extreme differences in metals, such as between iron and gold.  Set
MODE to TR2 to detect even greater distinction between metals.

Set DISCRIMINATOR to mid-range.  While you detect, adjust DISCRIMINATOR
to the best position.  The difference between iron and gold shows on the
meter (iron in the ferrous section, gold in the non-ferrous section).  As
you set DISCRIMINATOR higher, the detector becomes more sensitive to the
differences between aluminum and gold, but some small pieces of valuable
jewelry, such as small rings, may be over-looked.  Therefore, coin
collectors do not usually set DISCRIMINATOR higher.

Also, it first rejects small pieces of silver paper, then thick foil, and
finally metal objects like pull tabs from aluminum cans.


  Each time you use the detector, you must adjust DISCRIMINATOR.  Each
  expedition presents new challenges.

  Press Auto-Tune during operation to automatically return the pointer
  to the center.

Fine-Tuning the Controls

Set these controls:

  1.  TEST to NOR
  2.  MODE to VLF

Set the remaining controls to mid range.

When you detect metal, switch MODE between TR1 and TR2 to determine the
quality of metal.  Adjust all remaining controls to their desired
positions.  (See "Tuning the Detector.")


Keep the search coil in a consultant parallel position to the ground
throughout the sweep.  Move the search coil slowly from side to side,
covering about a 3-foot area, overlapping each sweep.  The threshold tone
should peak as you pass the target center.  (Hurrying will cause you to
miss targets.)

Note:  The search coil will not detect without motion.

Be careful not to swing the search coil upward at the end of each sweep.
The swing up can cause the detector to emit false signals.  Keep the
search coil parallel to the ground at all times but don't touch the
ground.  Hitting the ground may cause a false signal.


No detector is 100 percent accurate.  Various conditions and objects may
adversely influence metal detection.  Its reaction depends on a number of

  The angle at which the object rests in the ground

  The depth of the object

  The amount of iron in the object

  The size of the object

To pinpoint an object, the second time, go at right angles to the first
time, making an "X" pattern.

Note:  The target will be directly below the "X" at the point of the
       loudest response.

This allows you to detect some targets that were hidden the first time
due to the sweep direction.   If trash in an area is so heavy that you
get false signals, slow your sweep speed and use shorter sweeps.


  A good detection has a consistent rise and drop of threshold tone.
  A poor detection has irregular highs and lows in threshold tones.
  If the metal is in the shape of a circle, opposite reactions may

  A good target response repeats as you swing the search coil over
  the suspected target.  Trash-induced signals tend to not repeat.

  Recently buried coins might not respond the same as coins buried
  for a long period of time.

  Some nails, nuts, bolts, and other iron objects (such as old bottle
  caps) oxidize and create a halo effect around these objects.

A halo effect is caused by a mixture of natural elements in the ground
and the oxidization created by different metals.  Because of the metal
mixtures, target signals may not be in a "fixed" position.  This effect
makes these objects very hard to reject.  (See "Fine Tuning the


The threshold tone may vary slightly while you search due to soil
changes.  This does not usually affect the sensitivity of the unit and
should not require further adjustment.

If the threshold tone changes significantly, you might need to readjust
GROUND.  Sometimes the change in threshold tone is due to reasons other
than ground conditions and can be easily corrected by a simple procedure.
Raise the search coil one foot from the ground and push Auto-Tune.
Lower the search coil to the ground again.  If this does not correct the
problem, repeat the full procedure to set GROUND.  (See "Setting
GROUND.")  If you continue to have problems, contact your local Radio
Shack store for assistance.


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