Ambit International GDO is
the implementation of a design by G3WPO. Published as a kit in the
November 1981 Radio Communication using two single-gate FETs.
It's range was 1.6 - 215MHz, in 6 bands. It featured plug-in coils that
were not tapped, in order to improve reproducibility. It was widely
accepted and proved quite reliable.
Cirkit
The
Cirkit GDO
is the updated
G3WPO Mark II design.
Like its predecessor, it is also a kit. There were two problems
associated with the original circuit: 1) the original oscillator covered
a very wide range of 135:1. This resulted in a much less-pronounced
dip
at the lower end of each frequency range. 2) The sensitivity of
the wavemeter was not very good.
These problems were
addressed by changing the two
FETs to dual-gate
MOSFETs (3SK88*s) which
had the added capability of using a resistor in the coil to adjust gain
per range. The wavemeter insensitivity was improved by changing the
detector diodes to
Schottky barrier types, and adding a small current to
keep them in conduction.
It was determined that
this circuit operated up to about 240 MHz, but that stability was
difficult was difficult that high while maintaining good stability below
3 MHz. Consequently, the upper limit for this version was reduced to 170
MHz.
Other
changes/improvements include: reproducible design on one pcb; new
precalibrated scale; and both audio dip/wavemeter indications. This
improvement was published in the April 1987 issue of Radio
Communication.
B&W
600 The
B&W Model 600 Dip Meter
is an AC line-powered tube-type dip meter with 5 coils from
1.75 MHz to 260 MHz in
overlapping, color-coded ranges. The tube is an acorn type 955, with the
500 uA meter mounted on the side of the cabinet. Unlike several of its
lesser predecessors from other manufacturers, the
B&W 600 has a
transformer power supply.
B&W
331-A
"Little Dipper"
The
B&W Model 331 Dip Meter
is a battery-powered unit with 7
plug-in coil/dial combinations.
Frequency coverage is from 2 MHz
to 230 MHz. The '331 is unique in
that it uses a bent metal-flange dial attached to the coil. Their claim
is for +/- 3% accuracy. It also uses four 1.5V batteries instead of the
'standard' 9V battery. Weight of the mostly stainless-steel unit is
about the same as most similarly-sized units: 1.4 lbs ( 0.6 kg). See
photo and schematic below, under "Waters". Manufactured around June
1963.
Boonton 101-B w/UHF
head
Bud GIMIX:
BUD GIMIX
Model GX-79
from the Triplett
advertisement p.61, 1952 ARRL
Handbook, 29th Ed.
The
BUD Gimix is a multipurpose
unit requiring no batteries, or power supply. It is calibrated for
use on the 10,
15, 20,
40, and 80 Meter bands. No
additional coils are needed, as the one coil does the work on all
bands. It can be used as a Wave-Meter,
a Monitor, a
Field Strength Indicator,
and a sensitive Neutralizing
Instrument. Operating instructions supplied with
each unit.
The
former DL3QR,
Hans Ahlers,
put together a
'project' GDO, with a 'kitted run' of 50 GDOs! I was recently fortunate
enough to obtain one of these beautiful
GDOs. With an anodized panel,
and beautiful case workmanship, this is not 'just' a homebrew
GDO, but
rather an instrument of superb quality. Much of this information came
from the present holder of the
DL3QR
callsign,
Frederike John-to
whom I am very indebted. I have the complete unit, with coil. The photo
below was provided by the seller (in Germany)
Adolf Vollmer, DM2EBI.
I will add my own with details of this valuable find soon.
Das ehemalige
DL3QR, Hans Ahlers, put zusammen ein ' Projekt ' GDO, mit ' kitted
Durchlauf ' von
50 GDOs!
Ich war vor kurzem genug gl�cklich, eins dieser sch�nen GDOs zu
erreichen. Mit einer anodisierten Verkleidung und sch�ner
Fallkunstfertigkeit ist dieses nicht ein homebrew
GDO, aber eher ein
Instrument der gro�artigen Qualit�t ' gerade '. Viel dieser
Informationen kam vom anwesenden Halter des
DL3QR-Rufzeichens, John-zu
dem Frederike ich sehr verschuldet sind. Ich habe die komplette
Ma�einheit, mit Spule. Das Foto folgend wurde vom Verk�ufer (in
Deutschland) Adolf Vollmer, DM2�BI zur Verf�gung gestellt. Ich f�ge
meine Selbst mit Details dieser wertvollen Entdeckung bald hinzu.
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