The Heathkit GD-1190
“CoinTrack”
:
In 1978 Heathkit introduced a new metal loca-
tor. It is believed to originally have sold for
$119.95. This device was designed specifically
for finding small coins. The GD-1190 weighs
3.4 lbs. The over all length is adjustable from
22-1/2” to 45-1/2”. The small coil housing
measures 6” in diameter. The meter may be as-
sembled for left or right-hand operation. Power
is supplied by 6 AA batteries. An optional nicad
battery pack and charger are available. The cable
from the coil housing to the control unit is external
to the adjustable shaft and wraps around it. The
cable can be unplugged at the control unit.
Unlike the coil system of the previous metal lo-
cators, this locator uses a search coil but no
pickup coil. Instead of relying on the metal be-
ing located creating its own magnetic field that
is then sensed by a pickup coil, the GD-1190
relies on the metal detuning the resonance of the
coil and associated capacitance. The coil is ex-
cited by a stable 3.59 crystal oscillator divided
down to 56 KHz. Detection is done by a dis-
criminator circuit.
This is the first Heathkit metal locator to use
integrated circuits. The five ICs are an
LF211
FET comparator,
LM2902
quad op-amp,
CA3130
op-amp,
CD4011
CMOS quad NAND
gate and a
CD4024
CMOS binary counter. One
JFET and five bipolar transistors (one a Dar-
lington) are also used, along with 4 diodes (one
general purpose, one varactor and two zener
diodes).
External controls include
VOLUME
,
DIS-
CRIMINATE
,
TUNING
, a 4-position
MODE
switch and auto
TUNE
pushbutton. A meter,
speaker and
PHONES
jack mount on the con-
trol cabinet which also supports a handle. The
“CoinTracker” custom balances for less fatigue
during use.
GD-1190 Accessories:
Three accessories were available for the GD-
1190. The GDA-1190-1 nicad battery pack, the
new GDA-1190-2 Superex headphones and the
GDA-110-3 carrying case. In the Fall 1980
catalog these sold for $19.95, $11.95 and $11.95
respectively.
The accessory nicad battery pack can be
charged either from a car cigarette lighter
socket or from a standard 120V AC outlet.
The Heathkit GD-1290
“GroundTrack”
:
In 1979, shortly after the GD-1190 was intro-
duced, Heathkit introduced another metal loca-
tor, the GD-1290
“GroundTrack”
. In the Fall
1980 catalog it sold for $189.95. (Later it sold
for $219.95. The ad called this locator “Our fin-
est Locator”; it was also the last locator that I
am aware they built. Unlike the “
CoinTrack
”
this unit uses search and pickup coils (induc-
tion balance) like the older units, though its
circuitry is significantly advanced. Physically
this locator is similar to the “
CoinTrack
” in
size, weight and appearance, with some minor
variations in controls.
GD-1290 Accessories:
The GD-1290 uses the same three accessories
(the nicad battery pack, the Superex head-
phones, and the carrying case) that were avail-
able for the GD-1190.
Comments:
While I was is possession of manuals for the GD-
48 and GD-348. Finding information, or even a
clear schematic, for the other two units proved
inadequate to give a more thorough description.
GD-48 User Interview:
I got a chance to interview Ken -
W6HHC
on his
thoughts about the GD-48 Metal Locator.
Mostly his comments were positive. The kit was
easy to build, calibrated easily and operated as it
was supposed to do. He mentioned he liked to
take it along on the family outings to the beach;
his kids enjoyed searching in the sand too.
Ken did comment on two faults he had with the
GD-48. The first was that it needed to be ad-
justed whenever he took it out. However he
said that once adjusted it stayed in adjustment
HOM rev. new
Heathkit of the Month #53 - GD-48 Metal Locator
Copyright 2014, R. Eckweiler & OCARC, Inc.
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