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Heathkit of the Month #53:

by Bob Eckweiler, AF6C

GENERAL PRODUCTS
Heathkit GD-48
Metal Locator.

Introduction:

Buried Treasure? Aye Matey, I  was saving this 
series of Heathkits for September  as that is the 
month of  “Talk Like  a Pirate  Day” which falls 
on the 19th. Alas, so does the OCARC gatherin’. 
I expect a fun time!

However, our  rotating editor this month is Ken, 
W6HHC, and since he passed along manuals for 
the GD-48 and GD-348, I thought I’d honor him 
with an article on them for his turn as editor.

I’m sure many  a pirate of olde would have liked 
to  have a metal locator for finding those treas-
ures  that they  buried, only  to  later realize the 
map they  made was later used at the bottom  of 
the parrot’s cage.

Heathkit Metal Locators:

Heathkit used  the  nomenclature  “metal  ‘loca-
tor’”  instead  of  “metal  ‘detector’”   for  their 
treasure  seeking  products.  Heathkit  produced 
four models  over  the  years  that I’m aware  of. 
The  first  was  the  GD-48  which  was  listed  as 
new in the  1969 Summer  catalog. The  Deluxe 
GD-348 followed in 1972 and sold concurrently 
with the less expensive GD-48 for five years. 

Around 1978 Heathkit introduced the GD-1190, 
a third model designed specifically  for hunting 
small  coins.  In  ads  it  was  called  the  “Coin-
Track”. Around 1979 the last of the Metal Loca-
tors,  the  deluxe  GD-1290  “GroundTrack”  was 
released. 

Table 1  gives the production dates as best I  can 
determine with the catalogs in my files.

The Heathkit GD-48 Metal Locator:

The  first  Heath-
kit metal locator, 
the  GD-48 origi-
nally  cost $59.95. 
By  1976  the price 
had  increased  to 
$69.95;  but  in 
the  fall  of  that 
year  it was offered 
again  for  $59.95 
on  a  “save  $10” 
special.  The  last 
catalog  (1977)  I 
have  showing  it 
listed  had  the 
price back at the 
original $59.95.

The  GD-48  is 
shown  in  Figure 
1.  It  weighs  4 
lbs.  and  has  a 
10.5” diameter coil housing. The arm  length is 
adjustable from 26”  to  36”. It is powered by  a 
NEDA  #1602  9-volt  battery   (Heath  part  # 
GDA-48-1). This  is  a different battery  than the 
common  9V  battery  used in so  many  products 
today.  It is  rated at 850 ma/hr and  measures  
approximately  1.3” x 1.4”  x 2.7”. (The Eveready 
part # is  246). These  batteries  now run about 
$11.00  each  and  will  power   the  GD-48  for 
about  80  hours  of  operation.  The  cheaper, 
more available, NEDA #1604 may  be used but 
will provide  shorter operation time. The man-

HOM rev. new 

Heathkit of the Month #53 - GD-48 Metal Locator

Copyright 2014, R. Eckweiler & OCARC, Inc.

Page 1 of 7

Heathkit Metal ‘Locators’:

Model 

Name 

From 

To

GD-48 

(none) 

1969 

1977

GD-348  (none) 

1972 

1981

GD-1190  “CoinTrack” 

1978 

1983

GD-1290  “GroundTrack”  1979 

1985

Table 1

Fig. 1 Heathkit GD-48

Summary of Contents for GD-48

Page 1: ...ins In ads it was called the Coin Track Around 1979 the last of the Metal Loca tors the deluxe GD 1290 GroundTrack was released Table 1 gives the production dates as best I can determine with the catalogs in my files The Heathkit GD 48 Metal Locator The first Heath kit metal locator the GD 48 origi nally cost 59 95 By 1976 the price had increased to 69 95 but in the fall of that year it was offere...

Page 2: ...e jack and SENSITIVITY potentiometer which contains the OFF on switch The red battery lead is also connected to the switch The shaft and swivel are then assembled and the shaft is attached to the control panel and handle after the spiral cable is snaked through the shaft Next the coil housing top is con nected to the shaft the spiral cable is then sealed with a tube of supplied sealant where it en...

Page 3: ...with no input signal Q4 is just cut off When a signal becomes present Q4 conducts and and amplifies the changes in the input signal Transistors Q4 and Q5 share the same metal heatsink this is not for heat dissipation but to keep the two tran sistors at the same temperature and reduce drift in the differential amplifier The output of Q5 is further amplified by Q6 which is a basic common emitter amp...

Page 4: ...four transistors and handles the relaxation oscillator and active filter amplifier and one in the control handle that uses six transistors and processes the audio The audio processing board contains a fixed high gain amplifier followed by a temperature com pensated variable gain amplifier that is set by the S E N S I T I V I T Y control This am plifier drives a single transistor that drives the sp...

Page 5: ...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 119...

Page 6: ... I asked Ken what happened to his metal locator he said the swivel broke between the sense head and the arm and he finally abandoned it How ever he said it gave him good service for many years Acknowledgements I d like to thank Ken W6HHC for sav ing and passing along his GD 48 man ual after his unit broke beyond repair He also provided the GD 348 manual that he acquired from a friend 73 from AF6C ...

Page 7: ...HOM rev new Heathkit of the Month 53 GD 48 Metal Locator Copyright 2014 R Eckweiler OCARC Inc Page 7 of 7 ...

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