Racal Instruments RA6790/GM User manual

RACAL RA6790 INSTRUCTIONS'
1. Turn on POWER 2. Establish LOCAL control via LOCAUREMOTE button
3. INITIALIZATION: (a) Press and hold LOCK button, then AM button (on left
keypad,) releasing simultaneously; (b) Word 'REMOTE' will appear, then the
frequency and BFO digits will rapidly scan through their ranges-accompa-
nied by various changing sounds and tones; changing modes and levels
will fonow also; (c) If the sequence stops and displays a2digit byte num-
ber, the self-check has detected an error condition.
EXTERNAL SPEAKER CONNECTIONS
The LOUDSPEAKER OUT connections for the RACAL RA6790 are found on
J3 (DB25F) on the rear panel. Use a DB25P with the connections as listed
below:
LOUDSPEAKER OUT: pin 18 SIGNAL GND: pin 6 CHASSIS GND: pins 7, 8, & 9
TITLE
PACE NR,
: 10f1
RACAL RA6790 INSTRUCTIONS gg~~~~TlVE
nla
STARTUP I INITIALIZATION I TUNING VERSION:
with EXT. SPEAKER CONNECTIONS 1.0
FILENAME, jSECTION:
RACAL.SKD
HR\LOGOS
E. T. TANTON
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TeCHNICAL MANUAL
FOR
RA6790/GM
HF RECEIVER
'"
RCI84249
(R·2174)
(R-217;4A)
..
~ 1IO'1'ICl!:: TIlis dOClment COQ~ins proprietary
in.foJ:lllation furnished tor operation ~"'Iupport puJ:tlOses
only and not tor tllProcurement. ill~ "reprocunment and
manufacturing tiqhU are expressly reseJ:Ve<f":~?,ft9 such use
mey ~ .. de ot this document. either direcuy'"~J:":"-fndirectly.
vithOllt the ptior vritten con.ent of RaC~ CcIIIIIluni':Zltions
Inc.
SUPERCEDES ALL PREVIOUS EDITIONS
This document contains technical
intormation pertaining :0 tile ba~ic RA6790/GM 111" R.eceiver
and to the IIIOdUied RA6790/GM. !11" Receiver. "resultinq from
the addition of an 1D: level "r@turn ~oftware lDOdlfication.
That in.forsation perUininq to the basic RAfi790/GM 111"
a.c.iver is provided In Sections I throuqh VII of this
docuaent viler.... intorwation pertaining to the lIIOdifi"ed
1lA6790/Ql !!l' a.c.iver ia prOYided by difference d.!U in
Section VIII ot this dOCUlHnt.
Copyright
By
RACAL COMMUNICATIONS, INrORf'ORATE[)
5 Research Plaer.'-:
ROCKVILLE, MARVlMHl 20850
U.S.A.'
11 SEPTEMBER 198q

,
\
\
CHANGE NOTICE INSTRUCTIONS
THIS NOTICE IS FOR REFERENCE ONLY:
ALL CHANGE PAGES HAVE BEEN INCORPORATED IN TEXT
RCI84249
C2
ClWfGE
NO. 2
RACAL COMMCRICATIONS INC.
. lCJJC1tvILLE, MD 10 OC'l'OBER 1983
(Previous change notice .no. A82,
Issue No.1, June 1, 1982)
TECHNICAL.MANUAL
FOR
RA6790/GM
. .
HF RECEIVER
ReI 84249
RCI84249 (RA6790/GM) , August 1982 edition is changed as follows:
1. Remove old pages and insert new pages as indicated below.
2. New or changed text/tabular information is indicated by vertical bar in the
margin opposite binding edge of the affected page.
3. New or changed illustrations are indicated by a pointing hand adjacent to
the affected area.
4. New or changed schematic diagrams are indicated by highlighting affected
area.
5. Added or changed pages are indicated by including a change number adjacent
to the page number of affected page.
Remove Pages
Cover/Title Page
6-5 through 6-8
6-13 through 6-16
6-41 through 6-46
6-47 through 6-52
6-57
through 6-58
7-5/7-6
7-35/7-36 through 7-43/7-44
7-45/7-46 through 7-49/7-50
Insert Pages
Cover/Title Page
6-5 through 6-8
6-13 through 6-16
6-41 through 6-46
6-47
through 6-52
6-57
through 6-58
7-5/7-6
7-35/7-36 through 7-37/7-38
7-45/7-46 through 7-49/7-50
File this sheet in front of the publication for reference purposes.

CHANGE NOTICE INSTRUCTIONS
THIS NOTICE IS FOR REFERENCE ONLY:
ALL CHANGE PAGES HAVE BEEN INCORPORATED IN TEXT
RCI84249
C3
CHANGE
NO.3
RACAL COMMUNICA nONS INC.
ROCKVll..LE,
MD 14 FEBRUARY 1984
TeCHNICAL MANUAL
FOR
RA6790/GM
HF RECEIVER
ACI84249
(R-2174)
RCI84-24-9 (RA6790/GM), Change 2, 10 October 1983 edition is changed as follows:
1. Remove old pages and insert new pages as indicated below.
2. New or changed text/tabular information is indicated by vertical bar in the margin
opposite binding edge of the affected page.
3. Added or changed pages are indicated by including a change number adjacent to the
page number of affected page.
Remove Pages
Cover /Ti tIe Page
i through ii
3-17
through 3-18
3-23
through 3-24-
Insert Pages
Cover /Title Page
i through ii
3-17 through 3-18.2
3-23
through 3-24.2
File this sheet in front of the publication for reference purposes.

CHANGE NOTICE INSTRUCTIONS
THIS NOTICE IS FOR REFERENCE ONLY:
ALL CHANGE PAGES HAVE BEEN INCORPORATED IN TEXT
RCI84249
Cf4.
RACAL COMMUNICAnONS INC.
CHANGE
NO.4
ROCI<vn.LE.; MD 11 SEPTEMBER 1984
TECHNICAL MANUAL
FOR
RA6790/GM
HF RECEIVER
RCI84249
tR·2174) .
RCI84249 (RA6790/GM), Change 3, 14 February, 1984 edition is changed as follows:
1. Rem9ve old
;:>ages and insert new pages as indicated below.
~e"" or changed textltabular information' is indicated by vertical bar in the margin
opposite binding edge of the affected page.
Added or changed pages are indicated by including a change number adjacent to the
3. page number
of affected page.
4. New or changed illustrations are indicated by a poiming hand adjacent to the affected
area.
Remove Pages
Cover ITitle Page
vi
6-64
through 6-65
Insert Pages
Cove!" ITitle Page
vi
6-64 through 6-65
File this sheet in front of the publication for reference purposes.

ERRATA
SHEET
RA6790/GM
HF
RECEIVER TECHNICAL
!1ANUAL
Below
is
a
list
of
corrections
to
the
above
referenced
manual.
PAGE
1.
4-3,
4.2.1.2
4-5,
4.2.2.1
4-13
4.3.2.1
2.
4-27
4.3.6.2
3.
4-37
4.3.7.4
.:..
4-40
4.3.7.5
5.
4-41
4.3.7.5
CHA...'1GE
~IOT
Ie
E
~.:o.
A82
ISSUE
:W.
1
SECTION
IV
.
1
4
2
13
1 6
1
13
n 9
in
22
itS
14
REQUIRED
CH.A.'iGE
CIRCUIT DESCRIPTION
References
to
the
upper
limit
of
t~e
HF
band
should
Change:
Change:
Should
Change:
read
"29.999
:1Hz
"
not
"30
:1Hz".
,
to
read
"to
U2.~,
U22
and
U19A
and
t:19B".
"Paragraph
a "
to
"Paragraphs
4.3.7.2.
and
4.3.7.3."
read:
"The
TC
output
pin
15
of
t!
10 •
.•.
"
.
"Paragraph
b(3)"
to
"Paragraph
'::'.3.7
...
(3)"
June
1,
L982
l{A67':Ju/Ga

TABLE OF CONTENTS
Paragraph
Title
Page
SECTION I. GENERAL DESCRIPTION
1.1
.Electrical Characteristics
1-1
1.2 "
.' Mechanical Characteristics
" 1-2 "
1.3 Equipment Supplied 1-2
......
1.4'
..
Optional Equipment 1·,3·'·
1.5
Reference Data
1-4
SECTION
n. INSTALLATION
2.1 Unpacking and Inspection 2-1
2.2
Preparation for Reshipment and Storage
2-1
2.3
Installation
2-3
2.3.1
Rear Panel Jacks, Switches, Connectors
2-3
2.3.1.1 A1
OJ 1 power Input Connector and Voltage Selector /Fuse 2-5
Block Assembly
2.3.1.2
RF IN J 1 Connector
2-5
2.3.1.3 IF OUT
J2 Connector
2-5
2.3.1.4-
AF OUT J3 Connector
2-5
2.3.1.5 REF IN/OUT
J7 Connector
2-6
2.3.1.6 A6A1W1J1
Remote Control Connector
2-6
2.3.1.7 INT EXT
S2 Slide Switch
2:-6
2.3~1.8
GROUND Lug 2-6
2.3.1.9 PHONES
Jack, Front Panel 2-6
2.3.2
Installation Options 2-7
2.3.3 RA6790/GM
Receiver Options Installation Procedures
2-7
2.3.3.1
IF Bandwidth Filters
2-7
2.3.3.2
Remote Control Serial Asynchronous Interface
2-11
2.3.3.3 Independent Sideband
(ISB)
2-15
2.3.3.4- Line Level
Adjustment
2-17
2.3.4 RA6790/GM
Receiver System Connections'
2-18
2.3.4-.1 Power Input
Connections
2-18
2.3.4-.2 RF Input
Connector (J 1)
2-20
2.3.4.3 IF
Output Connector (J2) 2-20
2.3.4.4
AF Output Connector (J3) 2-20
2.3.4.5
Reference Input/Output Connector (J7) 2-20
2.3.4-.6
Remote Control Serial Asynchronous Interface Connections 2-22
(A6AlW1J1)
SECTION m. OPERATION
3.1
General Information
3-1
3.2
Front Panel Controls, Displays/Indicators 3-1
3.2.1 POWER
ON Toggle Switch 3-1
3.2.2 Manual Tuning Knob 3-1
3.2.3
IF GAIN Potentiometer
3-1
3.2.4
AF GAIN Potentiometer
3-3
3.2.5
MAIN LINE LEVEL Screwdriver-Set Potentiometer
3-3
i
'.

3.2.6
3.2.7
3.2.8
3.2.9
3.2.10
3.2.11
3.3
3.3.1
3.3.1.1
3.3.1.2
3.3.1.3
3.3.2
3.3.3
3.3.3.1
3.3.3.2
4.1
4.2
4.2.1
4.2.1.1
4.2.1.2
4.2.1.3
4.2.2
4.2.2.1
4.2.2.2
4.2.2.3
4.2.3
4.2.4
4.2.5
4.2.6
4.3
4.3.1
4.3.2
4.3.2.1
4.3.2.2
4.3.2.3
4.3.3
4.3.3.1
4.3.3.2
4.3.3.3
4.3.4
4.3.4.1
4.3.4.2
4.3.4.3
4.3.5
4.3.5.1
4.3.5.2
4.3.5.3
4.3.6
'\
I
TABLE OF CONTENTS (Cont.)
I-LSB LINE LEVEL Screwdriver-Set Potentiometer
Lefthand Keypad Pushbutton Switches
Righthand Keypad Pushbutton Switches
Left (Mode/Meter) Liquid Crystal Display (LCD)
Right
(Frequency Data) Liquid Crystal.Display (LCD)
. FAULT 'Indicator (LED)
.
Operating Instructions
RA6790/GM. Receiver Options Installation Check
-IF Bandwidth Filter Installation Check
Remote Interface Option Check (Serial Asynchronous Interface)
ISB Option Check
RA6790/GM Receiver/System Interface Check
.LOCAL/REMOTE Control Selection
LOCAL Control Operation Checklist
REMOTE Control Operation (Serial Asynchronous Inte~face)
SECTION IV. CIRCUIT DESCRIPTION
Introduction . ... ..... . .
Functional Theory of Operation
Primary Signal RF /IF /AF Section
RF Signal
IF Signal
AF
Signal.. .... . ........ .
Oscilla
tor Synthesizer: Section
First Local Oscillator Synthesizer
Second Local Oscillator Synthesizer
BFO Synthesizer
Automat:: ~ain Control (AGC) Section
Receiver ::ontro1 Section
Power Supply Section
BITE Functional Description
Detailed C:-cuit Description
RF Low P=...ss Filter, A1
First Mixer, A2
RF Signal Lowpass Filter and Mixer
First Local Oscillator Input Filter and Drive Amplifier
AGe Controlled IF Amplifier
Second Mixer,
AJ
First IF Amplifier
First Local OscUla tor Input Filter and Drive Amplifier
AGC Amplifier
Main IF/AF, A
4
IF Circuits
AF Circuits
AGC Control Circuits
Independent Sideband (ISB), A5
IF Circuits
AF Circuits
AGe Circuits
First Local Oscillator Synthesizer, A7
ii
3-3
3-3
3-4
3-4
3-6
·3-6 ...
.3-6.
3-7 .
3-7
3-8
3-9
3-9
3-11
3-11
3-18
4-1
4-1
4-1
4-1
4-3
4-4
4-4
4-4
4-5
4-5
4-6
4-6
4-10
4-10
4-12
4-12
4-13
4-13
4-13
4-13
4-13
4-15
4-15
4-15
4-17
4-17
4-19
4-21
4-23
4-23
4-23
4-23
4-25

TABLE OF CONTENTS (Cont.)
4.3.6.1 Operation of Phase Lock Loops
~25
~25
4.3.6.2 Digital Control
4.3.6.3
oscillator Control
~29
4.3.7 Second
LO and BFO Generator, A8
~33
4.3.7.1
Internal/External Reference Frequenc;:y
~33
4.3.7.2
Internal Mode
~33
4.3.7.3
External Mode
~35
4.3.7.4 Second Local
Oscillator
~.35·
...
4'.3.7.5 Beat t:requency
Oscillator (BFO) .4-37:
4.3.8
Receiver Control Section
q...;.41
4.3.8.1 Microcomputer Board, A6A2 4-48
4.3.8.2 Serial Asynchronous
Interface, A6A1 4-53
4.3·.9 Power Supply,
Ala
~57
4.3.9.1 DC Power Supply 4-57
SECTION
V. MAINTENANCE
5.1
General
5-1
5.2
Preventive Maintenance 5-1
5.2.1 Inspection for Damage
or Wear 5-1
5.2.2 Cleaning and Lubrication 5-2
5.3 Maintenance Support Equipment 5-3
5.4 RA6790/GM
Operational Checkout and Fault Isolation 5-4
Procedures
5.4.1 Initial Check 5-5
5.4.2
BITE Check
5-6
5.4.3
Al Low Pass Filter Check 5-9
5.4.4
A4 Main IF / AF Audio Check 5-10
5.4.5
A5 ISB Audio Check
5-10
5.4.6
A6A 1 Remote Serial Asynchronous Interface Check 5-10
5.5 RA6790/GM
Performance Tests 5-10
5.5.1 Frequency Tuning 5-12
5.5.2 Frequency Display 5-12
5.5.3 Frequency Stability 5-13
5.5.4 Frequency
Calibration Resolution 5-13
5.5.5 RF Gain
Control
5-13
5.5.6 Final
IF Frequency 5-13
5.5.7 Fixed/Variable BFO Operation 5-14
5.5.8 Audio
Output Power 5-15
5.5.9 Audio Distortion 5-15
5.5.10 Operation
After Restoration of Power 5-15
5.6 Board Level
Fault Isolation 5-16
5.7
Receiver Assembly and Disassembly Procedures
5-16
5.7.1 Preliminary
Procedure
5-16
5.7.2 Top and Bottom Covers 5-16
5.7.3 Al Module Removal 5-17
5.7.4 Al Module Installation 5-17
5.7.5
A2 Module Removal 5-19
5.7.6
A2 Module Installation 5-19
5.7.7 Module Removal 5-19
5.7.8
A3 Module Installation 5-20
5.7.9
A4 Module Removal 5-20
iii

TABLE OF CONTENTS (Cont.)
5.7.10
A4 Module Installation
5-21
5.7.11
A5 Module Removal
5-21
5.7.12
A5 Module Installation
5-21
5.7.13 .
A6 Module Removal
5-21
5.7.14
A6 Module Installation
5-22
5.7.15
A7 Module Removal
5-23
5.7.16
A7 Module· Installation
.5-23
5.7.17
A8 Module Removal
5-24- :
.'
5.7:18 .
A8 Module Installation
5-24-
.
5.7.19
A9 Module Removal
5-24
5.7.20
A9 Module Installation
5-28
5.7.21 AlO Module
?~emoval
5-28
5.7.22 AlO Module
installation
5-29
5.7.23 Edgelight Assembly and
Removal Procedures
5-29
5.7.23.1
Edgelight Re:7loval 5-29
5.7.23.2 Edgelight
In"::Jlation
5-29
5.7.24 Keypad
Removal and Installation
5-30
5.7.24.1 Keypad
Removal
5-30
5.7.24.2 Keypad
Installation
5-30
5.7.25
IF Bandwidth Filter Removal and Installation
5-30
5.7.25.1 Bandwidth
Filter Removal (Optional Plug-In Crystal
5-30
Filters Only) ~ ..
5.7.25.2 Banawidth
Filter Installation (Optional Plug-In Crystal
5-30
Filters Only) .'
5.8
Operational Fault Symptom Chart
5-31
SECTION
VI. REPLACEMENT PARTS LIST
6.1
In troduction
6-1
SECTION
Vll. SCHEMATIC DIAGRAMS
7.1 In
troduc: ;on 7-1
SECTION
VIll. DIFFERENCE OATA
8.1
In forma tion 8-1
8.3 Equipment Modifications 8-1
8.5 Scope
of Difference Data
8-1
8.;
Operation
8-1
8.9 AGC Level
Return
8-1
8.10
Parts List 8-1
8.12
Parts List Description
8-1
8.14 Usable
On Code Effectivities
8-2
8.15
Parts Ordering
8-2
8.16
Parts Suppliers
8-2
8.17
Schematic Diagrams
8-2
iv