The gold nuggets were found by Whites Engineer, Dan Geyer, who
designed the GMZ as a simple to operate, reasonably priced, gold detector. They
were all found on a recent vacation trip to the mountain area west of Winnemucca,
in Northern Nevada. That is a US Dime in the middle of the picture for size com-
parison. The gold is mostly in 3, 4, 5 & 6 grain pieces with a few larger ones.
The GMZ is a lightweight instrument that operates at a frequency of 50khz and uses
all of Whites standard Goldmaster search coils. The GMZ has only 3 controls and
features all metal, silent search operation with a unique ground rejection system.
The Sensitivity control knob turns the instrument power on or off and adjusts Gain.
The Ground Reject control knob adjusts the ground rejection range.
The Ground toggle selects either Normal or Salt operating modes.
The GMZ features an improved ground rejection system that significantly reduces
ground interference and false target responses. The rejection range increases as the
Ground Reject control is turned clockwise. Low mineralized ground requires a
narrow range for good rejection. Other soils loaded with black sand or hotrocks
require a wider range. The GMZ gives the prospector continuous control for the
ground rejection range required for maximum sensitivity to gold nuggets. The Salt
position provides the ability to search in desert regions with heavy concentrations of
conductive salt or alkali in the ground. The GMZ operates with the same 12 Volt
8 AA battery pack as Whites GMT Goldmaster & gets similar battery life which
usually exceeds 50 hrs. of operation. Simple operation instructions on back of page.
WHITES GMZ GOLD PROSPECTING DETECTOR
The GMZ is designed for fast and easy setup and operation.
The following procedure illustrates the use of the controls.
1/ Check that the battery pack is in position and the door is firmly latched.
2/ Set the Ground toggle switch to the Normal position.
3/ Turn the Ground Reject knob fully counter clockwise to the lowest setting.
4/ Turn the Sensitivity / Power knob On & set it to the factory suggested preset mark
5/ Sweep the search coil across the surface of the ground and listen for any sound
level variations produced by changing mineralization levels from spot to spot.
This will be evidenced by chatter or a sort of clicking sound.
6/ Now adjust the Ground Reject knob clockwise while sweeping or pumping the
search coil over the ground till the chatter diminishes or goes away.
7/ You might now place a small target, such as a small gold nugget or lead split shot
on the ground and pass the search coil over it in order to note the sound of a
target signal. The coil must be kept in motion while passing over the target. You
may criss-cross your coil over the target to mark the spot where the target is.
This Xing of the signal is the typical way to pinpoint the target.
8/ You will note that the GMZ, does not produce a threshold hum which is typical
of other gold detectors, but instead operates in silence. The only sounds you might
hear are targets, as demonstrated above, or chatter from extreme ground
variations. Continuous ground noises are an indication that the Ground Reject
knob should be corrected further clockwise. Never correct the Ground Reject
further than is necessary to control ground interference.
9/ You may use the Ground toggle set at Salt when prospecting in alkaline areas
often found on the desert. Particularly when wet, these areas produce a great
deal of interference and make it difficult or impossible to detect. You can reduce
this interference by using the salt position. With the Ground Reject knob set fully
counter clockwise, turn the knob clockwise ( to the right) till the noise is dimin-
ished. Never correct the Ground Reject further than necessary.
10/ As with any metal detector, the Sensitivity control is used to increase depth of
detection. However, when there is interference from environment or ground it
is always advised to reduce the Sensitivity to allow for interference free detecting.
Happy Hunting ........Dan Geyer and Jimmy Sierra
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