MARINE
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RADIO AND ELECTRONIC
EQUIPMENT
"ATALANTA" RECEIVER
TYPE 2207C
by
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G. L. DANIELSON M.Se. Tech., D.Se., A.M.I.E.E.
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F. C. MAYOH, B.E.M.
(lst ClassP.M.G. Certificate)
and
(lst ClassP.M.G. Certificate)
Handbook Re! R (S) 37.
------
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Marconi Marine" Atalanta " receiver
(Type 2207c)
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CONTENTS
PREFACE
SECTION 1
General Description
"-- .
1.1 Block Dlagrams
1.2 Frequency Ranges ...
1.3 Valves
1.4 Fuses
1.5 Front Panel and Chassis Layout
1.6 Specification
SECTION 2
Signal Frequencies
2.1
R.F. stages (Vl and V2)
2.2
Calibrating Oscillator (V13) ...
2.3
Calibrating action
".
Page
1
2
2
2
3
3
4
6
6
Frequency Changing
3.1
Frequency Changers (V3, V4 and V5)
Intermediate Frequency
4.1
4.2
I.F. Stages (V6 and V7)
Variable Selectivity
Desensitising and Muting
5.1
Relay Desensitising
5.2
Cathode Desensitising
5.3
Grid Desensitising
5.4
Muiiing Circuit
5.4.1 Under no-signal
5.4.2 In the presence
Detector, Noise Limiter and A.G.C. Circuits
6.1
Beat Frequency Oscillator (V9)
6.2
Balanced Demodulator .
6.3
Noise Limiter and A.G.C. Circuits
SECTION 3
SECTION 4
SECTION 5
conditions
of a signal
SECTION 6
...
8
9
10
11
11
12
13
14
14
15
15
17
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CONTENTS (Contd.).
SECTION 7
Audio Frequency
7.1 Audio Frequency and Output Stages (VI0 and VII)
SECTION 8
Power
Supplies
8.1 General
8.2 H.T. Supplies ...
8.3 L.T. Supplies ...
SECTION 9
REVISION
9.1 Points
9.1.1
9.1.2
9.1.3
9.1.4
9.1.5
9.1.6
9.1.7
9.1.8
9.2
Revision Questions
9.2.1
9.2.2
9.2.3
of Interest
R.F. Section (VI, V12 and V13) ...
Frequency Changers (V3, V4 and V5)
LF. Section (V6 and V7) ....
Detector/B.F.O. (V8 and V9)
Noise Limiter/A.G.C. ...
A.F. Amplifier and output stages (VI0 and VII)
Power Supplies (VI2)
Miscellaneous
Section A
Section B
Section C
Page
19
20
21
21
22
22
22
22
22
22
22
23
23
23
23
24
25
I
Appendix No. 1.
Appendix No.2.
Appendix No.3.
APPENDICES
Magnetostriction
Balanced Demodulator
Noise Limiter
(ii)
27
30
35
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PREFACE
Radio Officers, whether seagoing or under training and others
associated with marine radio, who are required to understand the
circuitry of communication equipment and other electronic aids to
navigation, have, in general, at their disposal an amount of radio
knowledge which they accumulated over a period of time, together
with the manual relating to the appropriate equipment provided by
the manufacturers.
It is usually found that the manuals, although excellent for
the purpose for which they are designed are not directly useful
for the immediate understanding of the circuit principles involved
in unfamiliar equipment and that a considerable amount of ground-
work is necessary before some of the circuit diagrams included in
the manuals can be re-cast in a form suitable for this kind of
study.
The authors of this series are engaged in the large scale
training of Radio Officers and, in addition, benefit from many
contacts with Marine Inspectors, Technical Assistants and sea-
going Radio Officers. They have come to the conclusion that a
considerable need exists for publications of a type which will
form a bridge between the standard of radio and electronic knowledge
likely to be possessed by reasonably advanced Radio Officers under
training and the kind of information provided by the manufacturers
manuals. In consequence this series of publications has been
produced.
In these booklets the circuits shown in the manufacturers
manuals have been broken down, re-cast and simplified to show only
those features which are essential to an understanding of the
method of working. The explanations are based on the assumption
of a knowledge of radio principles to a level approaching that of
the P.M.G. 2nd. Class Certificate examination. In this way it is
expected, and has in practice been found, that P.M.G. students and
qualified Radio Officers can rapidly acquire a good knowledge of
the methods of functioning of unfamiliar equipment without the
need to read through a quantity of basic theory with which they are
presumably already familiar, but with the assurance that anything
unusual or somewhat advanced- as for instance a balanced demodulator
- will be dealt with adequately.
The depth to which explanations are given is sufficient to
cover the needs of those studying for the P.M.G. Second and First
Class examinations and for such students in particular it is hoped
that section 9 will be helpful; in this section items of interest
are set out in a concise form and a number of revision questions
are posed. It is thought that this will assist in revision and
enable the student to assess his understanding of the circuits.
~
For sea-going Radio Officers or for those working on equip-
ment ashore, the publications present a straight-forward account
of the circuit action and include in the Appendices an account of
any unusual features or circuit elements, when this is thought to
be advisable.
If the booklets are used in conjunction with the appropriate
manufacturers manuals the user should acquire the necessary under-
standing and information to maintain the equipment in good working
order and to diagnose the cause of a fault, locate and rectify it
as necessary.
This series could not have appeared in its present form with-
out the kindly interest and effective help in the launching of the
project given by Mr. L.A. Rooper, Manager, Technical Information
Department, and Mr. F.E. Ash, Superintendent of Training, of The
Marconi International Marine Communication Co. Ltd., to both of
whom acknowledgement is gratefully made.
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PHONE.
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R93
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GRID
DESENSITISING.
R73
RCUIT DIAGRAM OF "ATALANTA" MARINE RECEIVER
FIG. I
GENERAL DESCRIPTION
Section 1
1.1 Block Diagrams
Section 1.2 gives details of the frequencies covered by each
of the ten ranges of the receiver and of the intermediate fre-
quencies employed. Block diagrams of the receiver, appropriate to
the various wave-ranges, are shown in Figs. 2, 3 and 4 and should
help the reader keep in mind the overall picture while studying
the explanations of the individual circuits.
RAI\ICTE ,
A.G,G. LINE
f1Cr.2
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Vl3
V3
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RANC1ES 3, 4 &5
FIG-.3
KANCrfS
FICr.4-.
Z.6,7. 8, 9 ~ /0
1
1.2
Range
"
"
"
"
"
"
"
"
"
1.3
Frequency Ranges
- - -
1.
- - -
2.
- - -
3.
- - -
4.
- - -
5.
- - -
6.
- - -
7.
- - -
8.
- - -
9.
- - -
10.
Valves
- - -
V1.
- - -
V2.
- - -
V3.
- - -
V4.
- - -
V5.
V6. - - -
- - -
V7.
- - -
V8.
- - -
V9.
V10 - - -
Vll - - - N37.
V12 - - -
V13 - - -
V14 - - - ECH81 or X719
400 - 800
800 - 1. 7
3.6 - 7.5
15.0
EF85 or W719 - - -
EF85 or W719 - - -
ECH81 or X719
EF85 or W719 - - -
ECH81 or X719
W77 cv
Z77.
D77 or EB91
ECH81 or X719
B309 or 6060 - - -
QS75/20
Z77
-
15
25 - 100
100
- 200
200
- 400 .kc/so
1.7 - 3.6
7.5
- 15.0 MC/s.
- 28.0 MC/s
15'
FCf-z...
25
kc/so
kc/ s.
kc/so
kc/so
MC/s.
Mc/s.
Mc/s.
- -
- -
- - -
- - -
- - -
- -
- - -
- - -
- - -
- -
- - -
- - -
- - -
- - -
- - -
- - -
- - -
- - -
- - -
- - -
variable-mu pentode.
variable-mu pentode.
triode heptode.
variable-mu pentode.
triode heptode.
variable-mu pentode. F"21 'lp6
pentode. Dv 1"3% C;I
double diode.
triode heptode.
double triode.
power pentode.
voltage stabiliser.
pentode.
triode heptode.
(optional fitting)
1.F.
1.F.
1.F.
1.F.
1.F.
1. F.
1.F.
LF.
1.F.
LF.
85 kC/ S.
700
kc/s& 85 kc/so
85 kC/so
85 kc/so
85 kc/ S.
700 kc/s & 85 kc/so
" " " "
"
"
"
" "
"
" " " "
" "
"
"
" "
G.cq 6
Metal rectifiers, MRl to ~ffi7,are of the single disc selenium
type.
1.4 Fuses
Both fuses are rated at 1.0 amp.
MAINS
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2
See Fig.5.
F.51
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F.S2 ~ -
FIG-. 5 -
ON/OFF
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COARSE LOGGING SCALE
FINE LOGGING SCALE
A.G.C.& NOISE LlMITER
SWITCH \
(ยง)
TUN\ SCACE
SCALE
(
POSITION OF TYPE 2361
/REJECTOR UNIT WHEN
/ FITTED.
LOUDSPEAKER
(WHEN FITTED)
AERIAL PLUG
& LEAD
FINE TUNING
EARTH BOLT
R.F. GAIN
PHONE JACK
A.F.GAIN
PASSBAND
SWITCH
RANGE SWITCH TUNING
FUSE MAINS
SWITCH
OUTLINE OF FRONT PANEL, CONTROL AND FUSE
POSITIONS OF 'ATALANTA' RECEIVER (TYPE 2207C)
FUSE
CONTROL
SYSTEM SWITCH
BANDSPREAD
OPERATING KNOB
PHONE JACK
FIG. 6
DESENSITISING LINK
TR I SKA
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00 B G I::::=-S'<J
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BEJG
61Skcfs
osc. IF.B
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CIOI
GB
swa 1.2&3.
CI3
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AERIALCI2 C9
1: @D
0 I 0 I I
0
CB6 CBI C76
C7
C4
0
C2
0
C66
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R123.R12'i.RI2it
COMPONENT LOCATION OF ATALANTA RECEIVER (TYPE 2207C) CHASSIS
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PLAN.
LP2
1.5
Front Panel and Chassis Layout
Figs. 6 and 7 show the front panel and the chassis layout of
the receiver.
Note:- The filter and A.e. power unit are mounted at the rear of
the case.
When operated from 200 volts D.e. the dropping resistance can
be fitted externally or at the rear of the case.
1.6
Specification
The specification for the receiver will be found in the manu-
facturers manua14 For general information regarding the minimum
permissible specifications of marine receivers, and other marine
equipment, the reader should consult the Merchant Shipping (Radio)
Rules, published by Her Majesty's Stationery Office.
3
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SIGNAL FREQUENCIES
2.1
L.
R.F. stages (VI and V2)
Lt
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Section
R3
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2
lo5V.
R2.3
A.4.C.
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FIG.8
Figures 1 and 8 refer.
On ranges 3, 4 and 5, valve Vl is cut-out of circuit by the
range switch SWA 5 which disconnects the cathode of Vl from the
H. T. negative line and thus stops the flow of current through resistor
R133 so that the cathode potential rises to some H.T. positive
potential thus holding Vl non~conducting. At the same time,
although not shown in Fig. 8, the wave-range switch connects L2
across the tuned circuit L1C16 so that L2 acts as a link coupling
between the aerial and the input circuit to V2, L3C37.
. On range 6 an I.F. rejector circuit, tuned to 700 kc/s, is
4
972
brought into circuit in series with the output of Vl. This is
incorporated as the R.F. stages of the receiver, when tuned to the
lowest frequency in this range - 800 kc/s - might not completely
reject a powerful unwanted signal on about 700 kC/Si any small
residuum of this, entering the I.F. section, would there receive
full amplification since the I.F. section is itself tuned to 700
kc/so The rejector circuit is not shown in figure 8.
At the upper end of ranges 4 and 5 there is the possibility
that the high value of image protection laid down in the specifi-
cation of the receiver (85 dB), might not be met. Consequently,
an image rejector circuit, C50L55, tuned to approximately 950 kc/s
is employed on range 5, while the same circuit with C50 paralleled
by another capacitor, C45, to reduce the frequency to approximately
550 kc/s, is used on range 4. These rejector circuits are included
in series with the anode load of V2 and clearly give the maximum
protection at, respectively, (950-2x85) kc/s and at (550-2x85)
kC/Si i.e. at 780 kc/s in range 5 and at 380 kc/s in range 4.
For information regarding the minimum performance permitted
in marine receivers see the Radio Rules referred to in Section 1. 6.
The single frequency changer technique used on ranges 1, 3,
4 and 5, with an I.F. of 85 kc/s, cannot be employed on range 2
since the frequency of 85 kC/s is included in this band. Accord-
ingly a double frequency change, as used on ranges 6, 7, 8, 9 and
10, is also provided for range 2.
The fact that the first I.F. is thus fixed at 700 kc/s would
give rise to tracking difficulties if an attempt were made to tune
both the signal frequency and oscillator circui t.sby means of gan-
ged capacitors; this can be seen from the following table which
shows that the required signal frequency change is more than three
times the corresponding oscillator frequency change.
LF. = 700 kc/s
Signal frequency
Osc. frequency
For this wave-range, therefore, the signal frequency circuits
are untuned and consist of an untuned transformer input with high
and low pass filters resulting in a broad band R.F. circuit cover-
ing the whole range 25 kC/s to 100 kc/so
Frequency selection in this range is provided solely by the
manual tuning of the oscillator.
In order to render the gain of the receiver as constant as
possible, over the wide frequency range covered, (15 kc/s to 28
MC/s), a small amount of negative feedback is applied to the
inputs of Vl and V2 by leaving resistors R35 and R23 in the cathode
circuits un-bypassed.
25 - 100 kc/s
725 - 800 kc/s
f max/f min = 4
. = 1.1
/
f max f mln
5