GDO
was one of the more successful tube-type,
AC line powered, GDOs.
It had a frequency range of 400kHz-250MHz
in 8 overlapping ranges. Even though it was a kit, it-as with all other
KIT
GDOs I am aware
of-used pre-wound plug-in coils wound to a 0.5%
accuracy on polystyrene forms.
A GDO
is basically a wide-range oscillator with a meter in the grid-return
line to indicate when the resonant frequency (of the tuned circuit it is
loosely coupled
to) matches the frequency of the GDO
oscillator. That happens because the tuned circuit-under-test absorbs
the energy of the oscillator, causing the
"dip" of the meter needle downwards. If
that oscillator is reasonably calibrated, you then know the approximate
resonant frequency of your coil-capacitor combination.
The
EICO
710
GDO
uses a 1:7
planetary drive on the tuning capacitor. It uses a
6AF4A in a Colpitts
oscillator circuit. It is transformer-operated, and uses about
10W of power. The
rectifier is a selenium
, and I would strongly recommend:
1) measuring
the DC voltage at its output; 2)
and then exchanging it for a suitable silicon diode. You should then
3) insert an
appropriate dropping resistor to cut the voltage back down to its
original value.
Measurements for the
EICO
710
GDO
are: 2.25" high;
2.6" wide; &
6.9" long. It
weighs approximately 3 lbs.
The exterior is Steel and Grey wrinkle finish.
The
EICO 710-A
GDO is a private-labeled solid-state unit
identical to the Leader LDM-815 and the
Loadstar KDM-6. I had never seen or heard
of one 'til I found this one on ebay.
I have finally obtained a nice
Eldico
GDO
with coils or info; and a
very
good condition Eldico
AntennaScope. The
GDO is at right. I was fortunate enough to
obtain one from the original owner-builder... complete with assembly
manual. I will be scanning the manual for BAMA
as soon as I can. The photo at right is NOT
the 'new' one.
The
GLOBAL G.D.O. Mk II
is another example of the
private-labeled Loadstar/NOVEX
modern
GDO line manufactured in Taiwan. This one
came from England, and an interesting thing about it is its box. I
gather these GDOs
come, OEM-style,
in a molded polyurethane foam box/container. Apparently without a
cardboard outer box. Reason for this supposition can be seen in the
pictures below. While the GLOBAL
box label is firmly affixed, as you would expect from any
commercially-made product, the box itself can be seen to have been (very
well) made from salvaged/surplus cardboard. Look at the printing on the
inside. This unit has seen little or no use, and it was probably the
original 9V
battery I removed upon arrival.
a
Grundig HZ Type 701
GDO
in
very good to excellent
condition. Acquired recently from
Australia!
I haveall
Heath GDOs
including:
the Models GD-1,
GD-1A,
and the
GD-1B.
Deserving special mention is the
Heath GD1-B (1955) Special LF Version
GDO,
his
very rare
GDO
is in absolutely MINT
condition; with:
original shipping box, instruction
sheet, conversion scale, and Auxiliary Coil
Set 341-A for ranges:
300kc-700kc and
700kc-1.9Mc (it'd be a shame to use
Hertz
here, wouldn't it!); The optional
LF coils and chart cost $3.00
in 1954!!. The associated
GD-1B was
$19.50. I also have the
HM-10A Tunnel Dipper:
one of the few (if not the
only)
commercial Amateur Radio applications of the
tunnel diode.
Also included in my collection
is an assembled (by me)
HD-1250
MOSFET GDO; and an
unopened, still-sealed-in-the-box
HD-1250
kit.
I
also have two models of the European version of the Heath
GD-1, the
GD-1U's.
One-as seen at left-that is a medium grey, with white letters. The other
is a lighter grey, with dark letters. I believe this is the older unit.
These are 220V European-only models I got from England. Very similar to
the U.S.
GD-Series, but a nicer design. Notice the EURO 220 VAC plug.
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