Eddystone model 750 specifications VK7AG
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THE EDDYSTONE mopeL “750”
A FINE BRITISH MADE COMMUNICATIONS RECEIVER OF
ADVANCED DESIGN AND | FIRST - CLASS CONSTRUCTION
See ————
The new Eddystone ‘* 750”’ Receiver employs the latest technique in
double superheterodyne circuits and combines high selectivity and
sensitivity with excellent signal-to-noise ratio. The tuning range is
continuous from 32 Mc/s. to 480 Kc/s., except for a small gap around the
Ist intermediate frequency of 1620 Kc/s. The horizontal scales on the
unusually wide, full vision dial are calibrated in frequency, these calibra-
tions all being linear. The tuning mechanism is afine example of precision
engineering. It incorporates a flywheel loaded high reduction ratio
gearing and an auxiliary vernier tuning scale which gives adequate
bandspread.
Separate RF, IF and AF gain controls combined with selectivity variable
over wide limits, ensure maximum performance under all conditions of
operation.
we STRATTON & co LTD
EDDYSTONE-WORKS - BIRMINGHAM > ENGLAND
; CABLES: STRATNOID BIRMINGHAM
ee a
SPECIFICATION OF THE EDDYSTONE
CIRCUIT. BANDSPREAD.
The receiver is an eleven valve double superheterodyne The ingenious mechanical bandspread mechanism gives
as follows : an almost linear scale equivalent to about 32 feet on each
Vale tuning range. The figures that follow apply to bandspread
coverage on the bands allocated to amateurs at the
Position Type. Function. Atlantic City Conference. Variation in the width of each
VI 6BAé6 R.F. Amplifying Stage. amateur band necessarily affects the degree of coverage
4 on V2“ ~ECH42 = Mixer | (S.F. to 1620 and against each band we have shown the number of
bag FA2--V3 6AM6 Oscillator |! Ke/s.) vernier divisions required to tune over the corresponding
: V4 + ECH42. Frequency Changer. (1620 number of kilocycles for each separate band width.
_ Kes. to 85 Ke/s.). —e
1 V5 6BA6 #_ IF. (85 Ke/s.). Tuning | Vernier Kilo-
Dior Ne _6AT6HPS 2nd Det., A.G.C. and AF. . Coverage! Divisions) cycles
) V7 6AL5 al N.L. and ‘'S”’ Meter diodes. BandWidth Vern ae in
V8 N78 ** _ Output Amplifier. Sale, |, sspcendigl eae
We eae re eter Srallater, 297 Mc/s. to28 Mc/s. | 34375"| 208 | 1700
VII VR/150/30 — Stabiliser. 21-45 Mc/s. to 21 Mc/s. | 7-5" 45:5 450
14:35 Mc/s. to 14 Mc/s. | 6-45 39 350
All the valves, with the exception of the rectifier and 73 Mce/s.to.-7 _Mejs. | 15° 91 300
stabiliser, are of the miniature all glass type, with either 4:0 Mc/s. to 3-5 Mc/s. | 61” 364 500
B7G or B8A bases. : ee 2:0 Mc/s. to 1-8 Mc/s. | 30” 182 200
INPUT IMPEDANCE, INTERMEDIATE FREQUENCY STAGES.
The aerial circuit is arranged to match into 400 ohm The first IF is 1620 Kce/s and the second, 85 Ke/s. This
feeder lines, but good results are obtained with aerials of combination results in high adjacent channel selectivity
widely varying impedance. and negligible image interference. The transformers
on a = are robustly constructed iand_parmeability tuned.—
TUNING RANGE.
The receiver is provided with four wave bands, the first BEAT FREQUENCY OSCILLATOR.
three overlapping and covering from 32 to 1-7 Mc/s. and This is constructed as a separate unit to ensure adequate
the fourth covering 1465 to 480 Kc/s. Each band is screening and a high degreeof stability. The pitch control
selected by a low capacity switch. The actual ranges are: \ gives a variation of plus or minus 3 Ke/s.
(1) 32 Me/s,to 12 Me/s.
(2), esa erssto™ 45 Mc/s... * AUTOMATIC GAIN CONTROL.
a4) 1465Fee
Ke/s.*to 480 ach Ke/s.
aS : The delayed A.G.C,
eae system maintains output level within
) oe ‘ cls 15 db for a change of 90 db input above 3 microvolts, at
N.B.—Range 4 includes the 500 Kc/s International 8 Mc/s. A.G.C. is switched off when the Beat Oscillator
Distress frequency. is brought into circuit.
TUNING. a * NOISE LIMITER.
Tuning is.by a gear-driven fires controlled mechanism The series diode limiter is extremely effective. It is
having a mean reduction ratio of approximately 150-1. controlled by a switch on the front panel. Special care
The scales are calibrated in frequency on all ranges. has been taken to avoid hum being introduced into the
Accuracy of calibration is within plus or minus 0-5%. circuit.
STRATTON
EDDYSTONE‘WORKS - BIRMINGHAM =
& CO LTD ENGLAND
{ CABILES: STRATNOID BIRMINGHAM
“750° COMMUNICATIONS RECEIVER
DRIFT. FINISH.
After 20 minutes from switching on, drift does not exceed The exterior is finished a fine ripple black. The controls
300 cycles for a plus or minus 5%, change in mains voltage. are mounted on an appropriately marked finger plate.
Chromium plated handles are fitted to front panel.
é
SENSITIVITY.
The sensitivity is better than 5 uV for a.20 db signal-to- CONTROLS.
noise ratio at all frequencies. The controls are :
Tuning B.F.O. Switch and A.G.C.
SELECTIVITY. Band Selector x Noise Limiter, on/off.
Variable from 30 to 60 db down for 5 Ke/s. off resonance.
R.F. Gain Standby Switch (with
LF. Gain long dolly).
A.F, Gain Mains, on/off Switch.
IMAGE RATIO. B.F.O. Pitch. Selectivity Control.
Better than 40 db at 30 Mc/s., and correspondingly higher
at lower frequencies.
VENTILATION.
OUTPUT IMPEDANCE. Ventilation has been carefully arranged to avoid undue
At the rear of the receiver are terminals for the connec- temperature rise in the cabinet.
tion of a speaker of 2.5 ohms impedance and on the front
panel is mounted a jack to take high resistance telephones.
Insertion of the latter automatically disconnects the ACCESSIBILITY.
speaker. The audio output exceeds 3.5 watts. Pick-up The receiver chassis can be taken out of the cabinet by
terminals are fitted. the removal of four fixing screws. The chassis is fitted
with protecting rails, so that when removed from the
cabinet, it may be Inverted wichouv damage to valves or
*S°* METER. components.
A socket is fitted at the rear of the receiver, into which
an external ‘‘S’’ Meter Unit — Cat. No. 669— can be
connected.
WEIGHT AND DIMENSIONS.
The weight is 40-Ibs. The dimensions are : Overall
ILLUMINATION, width, 162”; Depth, 10”; Height, 83’.
The scale is illuminated by 6 volt 1-8 watt bayonet fitting
lamps.
POWER SUPPLY.
Inputs of 110 volts and 200/240 volts, 40/60 cycles, are
GENERAL CONSTRUCTION. catered for, the power consumption from mains being
Aluminium diecastings are used for the front panel and approximately 70 watts.
tuner unit chassis. These provide an extremely rigid
foundation for the whole receiver. The power unit and The oscillator anodes and necessary screens are fed from a
I.F. output chassis are of heavy gauge brass, heavily stabilised high tensiqn supply.
nickel-plated and securely attached to the main castings.
The cover is of steel, fitted with lift-up lid, and heavily A socket is provided at the rear to enable the receiver to
rust-proofed. The most reliable of tropically finished work from a 6 volt battery in conjunction with an
component parts are used. external Vibrator Unit— Cat. No. 687/I.
tw’ STRATTON
EDDYSTONE WORKS - BIRMINGHAM =
& CO LTD
ENGLAND
CABLES: STRATNOID BIRMINGHAM
DIECAST LOUDSPEAKER
This efficient speaker consists of a 5” permanent magnet
unit mounted in a diecast housing 7” in diameter.
A special acoustic baffle is fitted and the tone is excep-
tionally good. Impedance 2.5 ohms. Finished ripple
black with chromium plated feet. Supplied complete
with lead.
Cat. No. 688.
SIGNAL STRENGTH METER
This “‘S'’ meter is designed for use with the
“750” Receiver. It is contained in a neat
diecast housing, finished a fine ripple black.
The necessary resistors, including the zero
adjuster, are fitted inside. The meter, which has
a 200 microampere full scale deflection, is
calibrated in ‘‘S’”’ units and decibels above
$9, on the basis of a 4db increase in carrier
strength for each ‘‘S’’ point. The leads terminate in an octal plug, which, in the case of the
“750 ’’ permits direct connection to the socket on the rear of the Receiver.
Cat. No. 669.
VIBRATOR POWER UNIT
This unit permits the ‘' 750°’ Receiver to be operated from a 6 volt accumulator. It comprises
a transformer, non-synchronous vibrator, rectifier valve (6X5G), on/off switch, and the necessary
filters which effectively prevent RF interference over the whole range covered by the receiver.
Smoothing is not included, since the choke and condensers in the receiver perform this function.
A heavy cable is provided for connecting to the battery and leads terminating in octal plugs for
attachment to the receiver. The unit is totally enclosed in a metal cabinet finished ripple black
to match the receiver.
Cat. No. 687/4
DOUBLET AERIAL
The Eddystone Doublet Aerial is a distinct improvement upon the single wire type of aerial.
The two arms forming the aerial proper can be strung in any convenient position (as high as
possible) and the flexible insulated feeder brought in through a small hole without the necessity
of additional insulation. Pick-up of electrical interference is minimised with a consequent reduc-
tion in background noise. i
Cat. No. 731 (50 ft. feeder)
Cat. No. 731/1 (100 ft. feeder)