Fisher F75 SPECIAL EDITION User Manual page 21

F75
LIMITED
Comprehensive Operating Manual & Guide to Metal Detecting
Frequency Shifting
One disadvantage of a highly sensitive metal detector is its susceptibility to electrical
interference from other electronic devices. If the detector chatters while the searchcoil is not
in motion, the cause is either electrical interference or internal circuit noise due to a high
sensitivity setting. If the detector chatters or emits intermittent false signals in the field, you
are also probably experiencing electrical interference. If you suspect electrical interference,
you may change the F75's operating frequency. This is a trial and error method to try to find a
frequency different from the suspected source.
To shift frequencies:
1. Hold the MENU button down. Do not release the button.
2. Push the trigger forward
OR pull the trigger back to change the frequency.
Each frequency change requires a push of the MENU button.
Each actuation will shift the frequency by one value.
The LCD will display the frequency, from F1 to F7. F1 is the lowest frequency. And the default
frequency. The F75 does not retain changes in the frequency setting, when powered off.
See the Search Techniques section of this manual for more information on electrical
interference.
28
Comprehensive Operating Manual & Guide to Metal Detecting
Discrimination Mode (continued)
Using DISC LEVEL in conjunction with NOTCH gives you a great deal of flexibility in deciding
which values to include or exclude from detection. Beware that this combination can be
confusing.
Here are some examples of NOTCH used in conjunction with DISC LEVEL
If Discrimination Level is set at 60, and you set the top-of-foil (21-25) notch between 21
and 25, then: top-of-foil range (21-25) is NOTCHED-IN (i.e. detected)
If Discrimination Level is set at 23, and you set the top-of-foil (21-25) notch between 21
and 25, then: 21, 22, & 23 are NOTCHED-IN. 24 & 25 are NOTCHED-OUT
If Discrimination Level is set at 15, and you set the top-of-foil (21-25) notch between 21
and 25, then: 21-25 are NOTCHED-OUT
NUMBER OF TONES (# OF TONES)
This menu selection allows you to select the number of audio tones emitted by the detector.
Different search conditions, search objectives, or personal preference will determine how
many tones you want to hear. With the below settings, you can decide to hear the same tone,
regardless of the target category, or have different categories of targets induce different tones.
The "# OF TONES" selections are:
1: SINGLE MEDIUM PITCH TONE.
All types of metal induce the same tone.
1F: MEDIUM-TO-HIGH PITCH TONE varying in proportion to target signal strength.
Large shallow objects will produce a squeal. The variable audio pitch provides you more
information about the detected object, but some people find the sound on strong signals
too annoying.
2F: TWO TONES.
Similar to 1F, except that iron produces a low-pitched tone regardless signal strength.
Useful if you want to hear all targets and want to identify iron. Most relic hunters prefer
this selection.
3H: same as 3, except that nickels produce a high tone.
3: THREE DIFFERENT AUDIO TONES. Iron produces a low pitch tone. Aluminum trash,
zinc pennies, and nickels produce a medium tone. High conductivity coins produce a
high tone. The 3-tone selection is often preferred for coinshooting. Most users will set the
discrimination level below nickels, at about 25, and dig only objects that produce a
consistent and repeatable high tone. NOTE: with this setting, steel bottle caps may
produce consistent high tones, similar to coins. See Capabilities & Limitations section for
advice on identifying steel bottle caps.
4H: same as 4, except that nickels produce a high tone.
Useful when coinshooting in a trashy area.
F75
LIMITED
21