K5AM                   home page                   boatanchor page

Clegg Six Meter Collection

During the 1960s, Clegg equipment was highly
regarded by VHF operators. The Clegg gear was
known for innovative designs and high quality

Shown above is a collection of nearly all of the 6 meter
Clegg radios. All of these Clegg radios have been
overhauled, are in excellent condition, and are on line
for instant use whenever the 6 meter band opens up for
short skip. Look for me on 50.4 MHz on AM.

Key to the photo. Descriptions are given below.

Top row, left to right:
A. Allbander
B. Thor 6
C. 66'er
D. Venus power supply
E. 99'er

Bottom row, left to right:
F. Interceptor
G. Zeus
H. Venus


A. The Allbander is an add-on HF unit for the Interceptor.
Powered by the Interceptor, it converts the HF range to 6
meters. This makes a fine HF receiver, with all the features
of the Interceptor. The up-conversion method is a precursor
of the system used in today’s modern radios. The Allbander
conveniently includes a speaker for the Interceptor.

B. The Thor 6 is an unusual radio. An early form of
transceiver, it uses a VFO in the 39 MHz range to convert
the 50-52 MHz range to a 10.7 MHz first IF, which is
followed by a 456 kHz IF. For transmitting in transceive
mode, the VFO is mixed with a 10.7 MHz oscillator.
Conventional transmit frequency control with 8 MHz or 12 MHz
crystals is an option. An even more unusual feature is a
provision for SSB or CW reception with a BFO at 10.7 MHz,
and panel-adjustable BFO injection level. The PA is an 6883
(like a 6146 except with a 12 volt heater), with a pi-
network and a rated carrier output of 40 watts. The power suppy
and push-pull 6BQ6 modulator unit is in a separate cabinet of
about the same size.

C. The 66'er is of conventional design. The receiver tunes
50-52 MHz with IFs at 10.7 MHz and 456 kHz. The transmitter
uses crystals or an external VFO. The PA uses a 2E26 with a
pi-network and a rated carrier output of 10 watts. The modulator
uses a pair of 6AQ5s in a standard circuit using a
modulation transformer.

D. The power supply for the Venus includes a speaker. The
design is conventional; many collectors will use a Heath
power supply if an official Clegg supply is not available.

E. The 99'er is similar to, but smaller than, the 66'er. The
PA uses a 7558 with a pi-network and a rated carrier output
of 5 watts. A single 6AQ5 is used in a dual-purpose fashion; as
receiver AF output stage, and as a modulator for the
transmitter, using the AF output transformer in a form of
choke modulation.

F. The Interceptor is a fine example of excellent design for
its time and style. The most notable feature is the large,
flywheel-loaded dial, with both slide-rule scale and small
circular logging scale. The receiver tunes the full 50 MHz
and 144 MHz bands. For the 50 MHz band, the receiver tunes
only one 1 MHz range at a time; this yields a nice dial
spread. The first injection is formed by mixing the VFO in
the 9 MHz range with a switchable oscillator, with four
crystals at about 30 MHz, yielding a total range of 4 MHz.
The IFs are at 10.7 MHz and 456 kHz. The main selectivity
element is a 10.7 MHz crystal filter with a bandwidth of 3.5
kHz, a good compromise for both AM and SSB use. (A later
version, the "B", has 2 filters, somewhat better for the
separate modes.) A completely separate internal unit
converts the 144 MHz band to 50 MHz; this arrangement makes
all the basic features and stability available on the higher
band. The receiver includes a noise limiter and an AF filter
for CW. It uses a total of 20 tubes, of which seven are the
6CW4 nuvistor.

G. The Zeus is the centerpiece of the Clegg collection. The
design was surely done on a "cost-is-no-concern" basis. In
2015 dollars, the selling price would be $4,327.44. Only
the very best circuits and components are used. The PA uses
an Eimac 4X150A external-anode tetrode, with forced-air
cooling, and 125 watts carrier output. The 150 watt
dissipation rating of this tube yields a large safety factor
of about 2. The modulators are a pair of 811-A, capable of
modulating far more than the 185 watt input of the PA in the
RF deck. The separate power supply and modulator unit, not
shown, weighs 80 lb. This heavy duty iron should last
indefinitely! The transmitter covers the full 50 MHz and 144
MHz bands, with continuous tuning. The VFO is in the 24-27
MHz range, with the usual crystal option. With a specially
designed circuit and adjustable temperature compensation in
the VFO, the stability is excellent. The RF line-up is 6BK7B
- 6AH6 - 6CL6 - 7558 - 7558 - 4X150. No cutting corners
here! Very conveniently, the mike jack and first four speech
amplifier stages are in the RF deck. To eliminate any
possibility of hum introduction, audio is then routed to the
separate modulator unit at a high level. The modulator unit
includes the very finest clipping and filtering method.
Rather than clipping at high level, at the modulation
transformer  secondary, and attempt filtering there, the
clipping is done at low level in the speech amplifier,
triggered by the actual modulation level. A 6W4 diode
detects the negative modulation peaks at the transformer
secondary and drives a 6C4 triode cathode-follower which in
turn sets the clipping level at a pair of 1N34A germanium
diodes way back in the speech amplifier. Following this
diode clipper is an effective L/C filter. Then the usual
phase inverter and modulator drivers follow. This feedback
clipping method gives exellent results. VHF operators in the
1960s were familiar with the exceptional sound of this
transmitter. A good modulation level (without splatter) was
a great advantage in working with the very weak 6 meter DX
signals during the sun-spot cycle peaks.

H. The Venus is a bit unusual as a 6 meter boatanchor from
the 1960s – it’s an SSB transceiver. It tunes 50 MHz to 50.4
MHz, and also runs CW and AM with inserted carrier. High
stability is achieved by using a VFO at 5 MHz, with no
multiplications. The first mixer for the receiver uses a
crystal controlled LO, converting to 14 MHz. A second IF at
9 MHz, using the VFO as LO, contains a crystal filter. A
third IF is at 440 kHz. The product detector is a 12BE6
pentagrid mixer/oscillator. The balanced modulator is a 7360
dual beam tetrode. The PA uses a 6883 (like a 6146 except
with a 12 volt heater), with a pi-network and a PEP output
of 45 watts.

rev. 2016-01-19

      k5am homebrew station       k5am home page       k5am boatanchor page