Swann CUBIC ASTRO 102 BX User manual

SERVICE
MANUAL
. ASTRO 102 BX
. TRANSCEIVER
eCUBIC .
. COM~UNICATIONS.INC.
5 .. 18,. DIVISION

····~SllvAN.
Adlvision of Cubic Communications, /nc.
To the Service Technician:
The ASTRO-I02BX is a modern, top-of-the-line, sophisticated
Amateur Band Transceiver utilizing state-of-the-art techniques
and design. The features that today's Hams want are built into
the unit, not marketed as "add on" accessories at extra cost
dual PTO's, Passband Tuning, Full or Semi Break-in, VOX, ew
Sidetone, RIT, Notch Filter, and more.
Whenever performance measured up to required standards, inte-
grated circuit technology was used in the design; where special
functions were required, or desired performance could not other-
wise be obtained, carefully designeddiscrete component circuits
were included, rather than accept compromised performance.
Every care has been taken to providelong, trouble-free life,
but the requirements of extra operating features, high perform-
ance design, and compact packaging demanded by today's Hams
results .in a unit necessitating a high degree of skill on the
part of you, the Service Technician. Tc assist you, this manual
has been painstakingly prepared. Take the time to thumb through
it; read and study the Theory of Operation section and the
Servicing Hints section; it will he time weIl spent, even for the
most highly qualified and experienced personnel.
It is you, the Service Technican, that will ultimately determine
how weIl or how poorly the radio will work, and therefore how
satisfied or dissatisfied our customers will be, in the long run.
If you have a suggestion or a problem, write or call our service
department. We'll listen, and help you all we can.
Sincerely,
CUBIC CO ICATIONS, INC.
D' ision
tV---
Sam"F. Am, K6TSD
President
SFA/lb
305 Airport Rd .• Oceanside, Ca. 92054 •Telephone [phone] Telex: 695435; ANS BK: CUBICOM, OCEN.

OCUBIC
CDMMUNICATIDNS
S""AItI DIVISIDN
Section One
General Information •••••• •••••••••••• ••••• ~·.l.l
Section Two
Specifica tions •••••••••••••••••••••••••••••• 2-1
Section Three
Receiver Theory of Operation •••••••••••••••• )-l
Section Four
Transmitter Theory of Operation ••••••••••••• 4-1
Section Five
Oscillator Theory of Operation •••••••••••••• 5-1
Section Six
Ancillary Circuits Theory of Operation •••••• 6-1
Section Seven
Servicing Hints ~ ................•.• .• ?-l
Section Eight
Servicing Data •••••••••••••••••••••••••••• ~ .8-1
Section Nine
Parts 1ists ••••••••••••••••••••••••••••••••• 9..;1
Since Cubic Communications is constantly striving to improve its
products, it reserves the right to make changes withoutnot1ce or
obligation.
The information contained in this document is the property of Cubic
Communications in conjunction with operating and maintaining the
ASTRO 102BX Transceiver. This information may not be copied, re-
printed, or disclosed to a third party, either wholly or in part,
without the written consent of Swan Division, Cubic Communications.
Entire contents@) 1980 by Cubic Communications.

-- ~~M~!~ATIC)NS
S.,.AIfI DIVISION
The Swan ASTRO l02BX is a 160M through lOM SSBamateur transceiverthat
features dua1 PTO's and frequency counter for splitfrequency operation with
digital frequency readout. Frequency selection is the only tuning necessary
when operating into a matched antenna with a VSWR of 1.7:1 or less.
Standard features include: Full break-in or semi-break-in CW operation;
narrow band crystal CW filter; two position CW transmit pulse shaping; VOX;
noise blanker; SSB transmit speech processor; true RF and IF gain controls;
peak reading wattmeter with FWD, REF, and ALC positions; variable AGC decay;
passband tuning; and audio notch filter. The basic single conversion design
has been proven in thousands of the popular Swan transceivers. Mechanical
and electrical designs are exceptional, for years of trouble-free operation,
even in a rugged mobile environment.
The unit is designed for fixed and mobile use with minimum interconnec-
tions. For fixed station operation an auxiliary speaker/power supply, model
psu-6, provides 13.6 V IC from 115/230 V AC. A matching antenna tuner, model
STZA, is also available.
The transmitter may be used for RTI'Y or Slow Scan TV, but operation in
these modes requires additional forced air cooling. See the operator's an-
ual for precautions to be observed when operatingin these modes. The ASTRO
l02BX includes automatic gain control (AGC) in the receive mode, and auto-
matic level control (ALC) in the transmit mode. CW sidetone is also provided.
~~::::=======:::~~;.;.;;.------------_.

..."
G'>
c
;lII;I
m
Ol
I
-'
, ""',
"",

OCUBIC
COMMUNICATIONS
SIVA_ DIVISION
~]p)~<Cll ~nCC(&û:n(Q)ffu~
General
Frequency Coverage*
160M. o ••••.••••••• ••• 1.8-2.0 MHz
80M •••••••••••••••• 3.5-4.0 MHz
40M •••••••••••••••• ?. O-? •5 MH:z
20M •••••••••••••••• 14.0-14.5 MHz
1.5M •••••••••••••••• 21.0-21.5 MHz
-lOM •••••••••••••••• 28.0-28.5 MHz
28.5-29.0 MHz
29.0-29.5 MHz
29.5-29.999 MHz
*Approximately 50 to 100kHz overrange provided on each band.
Frequency Control: Dual PrO with 6-digit frequency counter and RIT control.
PTO Modes of Operation: A only; Receive A-Transmit B; B only; Receive B-
Transmit A; External LO.
Modes of Operation: 88B with selectable sideband. CW with automatic 800 Hz
offset on transmi tand full or semi-l:n:'eakin.
Power Input Requirements: 12-14 V :IX: negative ground only. No damage up
to 15 V:IX:. 20 amperes peak current.
Electromagnetic Interference:
Transmit:
Receive:
Five element low pass filter on each band.
Five element lowpass filter plus three pole bandpass
filter on each band.
Dimensions: 6.375" H x 14.25" Wx 13.25" D
16.2 cm x 36.2 cm x 33.7 cm
Weight: 23.5 pounds (10.6 kg)
Rear Panel:
Power connector:
Pin 1
2
3
4
5
6
13.6 V :IX:
Ground
Ground
(used for accessories)
13.6 V:IX:
Ground
13.6 V :IX: fused to 3amps (used for accessories)
Antenna connector: UHF (80-239)
External speaker/phones: Phone jack
External relaYl RCA jack
2-1

OCUBIC
COMMUNICATIONS
SIIW .. III DIVISION
Key:
RCA jack
EXT. Modulation: RCA jack
Receiver Selectivity: SSB and CW--2.4 kHz OOndwidth, two 8-pole crystal
filters with shape factor 1.4; 6 dB to 100 dB
Fuse:
Ext. L.O.:
Circuit Design:
Receiver Sensi-
tivity:
Image Rejection:
Passl:and Tuning:
Dynamie Range:
Audio
Output Power:
Meter:
Circuit Design:
Power Input:
Power Output:
Unwanted Sideband
Rejection:
Harmonie Output:
3 amp fast blow
RCA jack
R
.1
ecelver
Single conversion to 9.00165 MHz IF using double 001-
anced mixer. Exceptional immunity to overload and cross
modulation.
10 dB S+N/N typical at 0.35 uV
Better than 60 dB
CWN--300 Hz l:andwidth. IF crystal filter in series
wi th one 8 pole SSB filter
SSB and CW eight pole cutoff continuously variabIe
high pass or low pass. LED readout shows equivalent
audio passband.
CWN--IF crystal filter continuously tunable over 300 to
3000 Hz with passband control
AGC greater than 100 dB; third order intercept +15 d.Bm
Greater than 3 watts into 4ohms.
S-units from 1 to 9; 20, 40 and 60 dB over S-9
Transmitter
Excellent hannonic and TV1 suppression. ALC limits SSB
peak power and CW power to 100 watts output.
235 watts PEP input at 13.6 V 00 input
100 watts PEP into 50 ohm non-reactive load at 13.6 V00
>60 dB down at 1000 Hz audio note
?45 dB below peak power level
Carrier SUPJlression: >50 dB below peak power level
2-2

_CUBIC
COMMUNICATIONS
SMFAIfI DIVIBION
Spurious Output:
Transmit Control:
(for SSB)
CW Transmit:
Microphone Input:
Audio Response:
Meter:
Coolingl
VSWR Shutdown:
> 55 dB below peak power level
PI'T and VOX standard
Full or semi-breakin with sidetone standard. Automatic
800 Hz offset on transmit frequency.
47 kO input impedance
)00 to )000 Hz i6 dB
In receive mode, reads S units and dB over S-9; in
transmit mode, reads peak power selected by meter
switch IForward power 106 watts full scale, reflected
power 10 watts full scale, or reads ALC.
Large capacity heat sink fins supplied. For SSTV, RTTY,
and semi-continuous transmit, forced air cooling such as
a small "muffin" fan on heat sink fins is required.
Full power up to VSWR= 1.7:1
Approximate limit ratio asfollows:
VSWR
1.7:1
2.0:1
).011
Open or short
Percent Power
100%--
80%
60%
25% (equivalent voltage)
"

OCUBIC
CDMMUNICATIDNS
5' •• ", DIVISIDN
Bandswitch and Low Pass Filters ••••••••••••••••• 3-l
Preselector oe ••••••••••••• •• 3-2
First M-ixer ••• ' •••••• 0 •••••••••••••••••••••••••• •3-3
Noise Blanker Gate •••••••••••••••••••••••••••••• 3-4
Filter, Buffer, and Post Filter Amplifier ••••••• 3-5
AGC Attenuator •••••••••••••••••••••••••••••••••• 3-5
Pass band Tuning ••••••••••••••••••••••••••••••••• 3-6
CW Narrow Filter •••••••••••••••••••••••••••••••• 3-7
Main I.F. Amplifier ••••••••••••••••••••••••••••• 3-8
Product Detector/Audio Mute ••••••••••••••••••••• 3-8
Notch Filter ...................•.•....•......... 3-9
Audio Power Amplifier/Receiver Mute ••••••••••••• )-9
Automatic Gain Control ••••••••••••••••••••••••• 3-l0

I
---------------------,
NarE: Component designations used in the "Theory" sections of this manual
are the shortened numbers as they appear on the schematic diagrams. To de-
termine complete component designation, the boardjlocation numbermust be
added af ter the letter or letters. See the "Note" in the first portion of
the "Parts" section of this manual.
Schematic diagrams contalned ~n the "Theory" sections of this manual
are simplified to help in the understanding of the operation of the circuit;
they may not always, therefore, be sufficient for troubleshooting purposes.
When servicing the equipment, it is urged that the technician use only the
schematic diagrams included in the "Servicing Data" porti on of this manual.
"I.c)
3-1
*CIIO
RECEIVE ANTENNA
IWITC" IN.
r - - - - - - - ....DSWITCN - - - - - ,
I LIQI LIQ2
I
I
I
I
I
I
I
"It"
LlNI
TO RX elol ca ~
I"PUT C>--ft--"'--1~ et-------oo TO Ut,
I1101
"131 RI02 I
TO
_1Q1.
O! ..
BANIBWITCH AND LOW PASS FILTER BOARD
---- -- --- ""'--..-;...;;;..
The received signal
from the antenna connec-
tor is passed through one
of six low pass filters,
which are also usedin
the transmit condition.
Each is composed of two
inductors and three cap-
acitors, yielding a five
pole filter for each band
(160
through 10 meters).
Note that the same filter
is used for all segments
of the 10 meter band.
The
filters are sel-
ected by SlOl and Sl02,
sections of the BAND sw-
i
tch. From SlOl, the
signal is passed to relay
KlOl, through C122, and
through Cl Ol. From there
it is routed to the input
of the preselector board.
Receiver antenna switch-
ing is accomplished by Kl Ol ,
which is activated by Ql02.
When the receive ("R") line
is high, as it is in the re-
ceive condition Ql02 is bias-
ed to saturation, energizing
KlOl and connecting C122 to
the output of the selected
low pass filter. Since the
collector of Ql02 is low when
it is thus saturated, QlOl is
in a non-conducting condition
and has no effect. However,
when the "R" line is low, as

OCUBIC.
COMMUNICATIONS
S.,A_ DIVISION
as it is in the transmit condition, Ql02 is cut off, and its collector vol-
tage is high. This biases QlOl on, providing a path to ground for any tran-
smit signal coupled across the open contacts of KIOl due to stray capaci ty •.
In this manner, the input of the receiver is protected during transmission
periods.
SlO), a part of the BAND switch, is used to provide a voltage to each
of ten control lines, depending upon its position. There are separate con-
trol lines for the 160, 80, 40, 20,15, 10A, lOB, IOC and 10D positions, and
an additional line, which, through CRI02 through CRI05, is high for any of
the 10 meter positions of the BAND switch. These control lines are used in
other sections of the transceiver.
PRESELECTOR
TO Itll
lAND
PItlAIiPS
It,.
PRESELECTOR
BOARD
INPUT SWITCHIN.
RIl4
CliO
RII3
v0
•
10 M lAND !fILTER
~C10'
TO ALl:
Itll7
0--"'--1> TO 0101
OT" o--"'--I>TO Til P1tE:AIIP
OR"
ClOII
Til IN 0---4'- ....... ...1
J13~
Ril IN CI07
JI32 0---41-..- .... ..,
1:119 ~
In the receive condition, the transmit ("T") line is low. Thus, CRI09
in the input circuitry of the preselector is reverse biased, and the TX IN
jack is effectively open circuited.
LI02 is an RF choke to prevent sig-
nal from being bypassed to ground
through CI09 on the "T" line.
On the other hand, the "R" line
is high in the receive condition,
and is connected through RF choke
LIOl to CRI08, which it biases to
an "on" condition. RIl) provides
aground return and the voltage
drop across it reverse biases the
"off" diode. ClIO is a DG blocking
capacitor, and passes the signal on
to the input of the preselector
band filters. Rl14 acts as a DG
return for the switching currents
for the filter selection circuits,
and provides reverse bias to the
"off" diodes.
There are six band filters in the preselector (only one is used for all
four segments ofthe 10 meter land). These filters are selected by the BAND
switch, utilizing the voltages on the control lines from SlO), as mentioned
earlier. For discussion purposes, only the 80 meter filter will be consid-
ered.
The voltage from the 80 meter control line is coupled through isolating
resistor RIl?, the primary of TI04, and CRl12 to the output of the input sw-
itching circuit previously dis-
cussed, wh ere it is provided
wi th a ground ret'l.Q3.. path th-
rough Rl14. Cl19 frovides a
~.
ground for the signal at one
end
of the J?rimary of T1.04. The
signal is then J?assed through FitOM I:ltll2
diode sw! tch CRl12 to T1.04, Wh_CliO
ile the voltage drop across R-
114 reverse biases the corres-
pon ding diode switc;:hes in the
other filters.
-2
•
------------------

OCUBIC
COMMUNICATIONB
5 .. 11", DIVIBION
0104
R14'
CI74
RI"'", CI73 Rl(
r-- ........JVvv..,1--0OUT
J13.
R14.
CRI24
R
136
RI34
0105
.... --- ..... ---,CI ••
+IO.5V
RECEIVE PREAMPLIFER
RI33
I1
LIO'
.---tt~~.p TO 0102
RI31
.:I:. CI.4
? CRI22 CRI23 ':" R14.
+IO.5V
R'"
FROM
ALC ;>-"V'oAr-t-.
The secondary of Tl04 is resonated by the C120-C122 series combination,
and they act as an impedance transformation voltage divider. Tl05 and C121
form a
series resonant circuit, and its output is coupled to C124-C125, wh-
ich again transforms the impedance of the signal path, and also resonates
with output transformer TI06. The combination of the two parallel rêsonant
circuits and one series resonant circuit forms a bandpass filter of excel-
lent characteristics. Output switching is provided by Rl18, in conjunct ion
with CRII), in amanner identical to the input switching scheme.
The
output of the preselector filters is coupled to the preamplifier
stage, QlOl, via autotransformer Tl19 and coupling c~pacitor C163. R127
provides a De path to ground for the switching diode, and provides reverse
bias for the "off" diodes in the other filters, while C159 effectively gr-
ounds the bot tom of Tl19 for the signal •
.
Bias for QlOl is pro-
vided both by the source
circuitry and the R128-R-
129 combination. So far
as gate two is concerqed,
the bias is determined by
the source network as weIl
as whatever is applied to
it via the ALC line. CR122
and CR123,. biased in the
forward direction by the
voltage applied by R150,
provide a fixed drop of
approximately 1.4 volts,
while additional bias is
supplied by the drop ac-
ross source resistor R132.
C160 and C161 are both by-
passes.
Signal from the drain
of QlOl is taken via C165,
af ter being developed ac-
ross load LIO). R131 and c164 form a decoupling network for the supply
line.
In the receive condition, the "R" line is high, causing Ql06 to satur-
ate, thus lowering the voltage on the base of Ql05, causing it to cease con-
duction. Diode switch CR124 is then reverse biased by the voltage drop ac-
ross R145 , allowing Ql04 to operate in anormal manner. Bias for Ql04 is
derived by R134 and Rl)6, while R149 serves to prevent instability. Output
of the preselector is taken from the emitter of Ql04 via Rl44 and C173 and
coupled to the receiver input of the exciter board.
EXCITER BOARD--FIRST MIXER
Af ter passing through the preselector and being amplified by the pre-
amplifier, the received signal is connected to mixer ZlOl via CI02, a block-
ing capacitor. Local oscillator signal, brought to the exciter board thr-
ough JI05, is coupled via blocking capacitor C164 to the base of amplifier
Ql14. . Bias for Ql14 is developed in a conventional manner via the R167~R168
voltage divider. The emitter resistor of Ql14 is divided into two Parts,

+IV
o
Rl78
RIOl
CIC!)
I------::-:-~Hq.
IF ûUl
f
RI73
FRaM
"""'1 f--"VV'v+e+-...-AAfV--<PA SlA 5
CONTROL
Ll~E
L.o. AMPLIFIERS
8 Ig MIXER
RX tN
JIl~ ()---j
fr~O:M~E' CI02
L 0 IN
OCUBIC I
COMMUNICATIONS
SMlAIfI DIVIBION
R164 and R165. While the former is
bypassp.d in the usual manner, the
latter is not, and a signal suit-
able for driving the display freq-
uency counter is taken from across
it, via R166 and c16J.
Arnplified L.O. output is taken
from the collector of Ql14 and co-
upled to the base of Ql15. Again,
bias is conventional, being devel-
oped by Rl?l and R172. The output
of Ql15 is taken across its emitter
resistor, Rl?J, via C16? and R174,
and coupled through R17? and c168
to the base of mixer driver QI01.
The P.A.
Bias control line is high
in the receive condition, thus re-
verse biasing CRI04, preventing the
L.O. signal from being shunted to
ground by C169, as it would be in
the transmit condition. I
Bias for Q10l is developed by RI04 and RI07, and CI04-RI06 form the us-
ual emitter circuit. CIOJ and RI05 form a feedback network, which, in con-
junction with Rl?? and Rl?4 set the gain of QI01. For amore complete dis-
cussion of feedback amplifiers and the1r operation, refer to the "Servicing
Hints" section of this manual.
NOISE BLANKER GATE
CIII
N.B. PULSE
FIR5T I.F. AMPLIFIER a
NOl5E BLANKING GATE
RII4
+IO.5V
Ril'
RI12
FROM CIO ... 6 ...... r-+-I
ZIOI >-i
The output of the first
mixer, ZlOl, now at the I.F.
frequency, is coupled to the
first I.F. amplifier, QIOJ,
via blocking capacitor cl06.
Rlll and Rl12 form the bias
network, while emitter res-
istor RIIO is unbypassed,
providing some degenerative
feedback. Output is devel-
oped across a parallel-tuned
resonant circuit composed of
the primary of TlOl and CI09.
Rl14
and CIO? form a decoup-
ling network, while the lat-
ter also places the upper
end of the pr1mary of nOl
at AC ground, so that CI09
is effectively in parallel
wi th TI01.
The secondary of TIOl presents a signal at low impedance, which is
coupled through noise blanker gate Ql04 to the primary of TI02, where it is
stepped back up. Cl12 resonates the secondary of Tl02. When the noise bl-
anker circuit detects a noise pulse of sufficient amplitude, the gate of Q-
104 is fed a positive pulse through CRI01, effectively cutting it off and
3
·4

o ~~M~!~ATIONS
S.,AItI DIVISION
opening its source-to-drain path, thus opening the signal path. Otherwise,
a ground is applied to the gate via RIIJ, keeping Ql04 in an "on" condition.
Clll and RIIJ serve to lengthen the pulse at the gate of Ql04 to ensure
positive blanking.
FILTER BUFFER, FILTER, AND POST FILTER AMPLIFIER
+IO.5V
TO
0108
RI19
L10Z
CII9
.r
Il,~ ..
LIOI
FILTER BUFFER, FILTE'R, AND
POST FILTER AMPLIFIER
RIIS
+IO.5V
CII5
~
C1I3
>It-+--H..
FROM
TIOZ
From Tl02, the signal is
coupled to filter buffer amp-
lifier Ql05 via blocking cap-
acitor CIIJ. Bias is dev-
eloped by Rl15 and Rll?, wh-
ile emitter resistor Rl16 is
unbypassed, providing degen-
eration. Output is taken ac-
ross collector load LIOl and
coupled through blocking cap-
acitor Cl14 to the first I.F.
filter, FLI01. Rl18, CI08,
and Cl15 are a decoupling
network.
From filter FLI01, the
signal is coupled through C-
116 to the base of post fil-
ter amplifier Ql06, which is biased by R120 and R121. In the transmit con-
dition, Ql06 acts as an emitter follower (discussed in detail in the Trans-
mit section of this manual), while in the receive condition, the output is
taken from the collector af ter being developed across load LI02. Cl18 is a
blocking capacitor. Note that the use of inductive loads and unbypassed em-
itters in the stages preceeding the AGC attenuator ensure good strong signal
handling capability.
AGC ATTENUATOR
From QI06, the received I.F.
signal is coupled through Cl18
and R12J to AGC attenuator PIN
diode CRI02, and thence via C120
to gate one of pass band tuning
first mixer, Ql08. AGC voltage,
when required, is applied to the
base of AGC driver QlO? via volt-
age di vider R129-RIJO·. Current
is then supplied to the PIN diode
via R124, causing it to conduct
to a degree determined by the AGC
voltage; it acts, in conjunction
wi th R12J, as a varia ble voltage
divider, similar in effect to a
conventional volume control, and
thus provides the AGC action re-
quired. Up to about 50 dB of at-
tenuation is available at this
point.
ASC
I1
C12!l TO PeT
..- ..... -IT FILTU
I.
C124
f-J'\A/' ............ --1HH----J ., '='
~"A ---, TO QIO.
1.F. AGC ATTENUATOR AND
PBT II! MIXER

-- ~~M~!~~TIONS
S""AItI DIVISION
RI!lO
osc-
R214
TI06
RI!l1
CWH
LINE
~ ~
CI1I9
C/48
f
+IO.!lV
RI42
U04
+IO.!lV
I!.'::
RI!!4
Rl!l' -=
FROM
PITO
RI!l2
PST FILTER AND
DRIVERS
+IO.5V
2!!i1 PST MIXER
RI!l1
RIS.
FROM
QII2 ()-"''oIV~~HI--'''''':''''l
PASSBAND TUNING
QI08, a dual-gate MOSFET, acts as a subtractive mixer, with the first
I.F. signal applied to gate one, and the passband tuning oscillator signal
applied to gate two. Bias for gate one is developed across RIZ7, while con-
necting gate two to the source via RIZ8 makes it operate without bias. Out-
put of Ql08, nowat the pass band tuning I.F. of 13.8 MHz, is taken fr om its
drain. 110) and CIZ4 form a parallel resonant drain load. C125 is a coup-
ling capacitor, routing the signal to the SSB filter via QIIO and to the CW
narrow filter via Ql09.
QlIO,
conventionally biased,
acts as an emitter follower to
drive the SSB filter, FLI02. Af-
ter passing through the filter,
the signal is coupled to Qll2
via Cl)6. Qll2 is also an emit-
ter follower, with its output
developed across Rl44 and bias
developed by the Rl42-R143 com-
bination. Cl)8 is a blocking
capacitor.
Wh en operating in the CW
narrow mode, voltage is applied
to the CWN line through R150 to
diode switch CRIO). This volt-
age reverse biases the base-emitter junction of Qll2, causing it to cease to
conduct, and thus breaking the signal path. Also, Cl39 shorts the signal
path through CRI03.
Signal from the CWN filter
amplifier Qlll (covered later)
and from the SSB filter are coup-
led to gate one of the second PET
mixer Qll). Rl48 and R151 are
isolation resistors, and Rl52 is
the gate return resistance for
QlIJ, which is also a subtractive
mixer. Oscillator energy is co-
upled to gate two of QlIJ in the
same manner as i t was to the first
PET mixer, and the bias arrange-
ment is also the same. Output is
taken via Cl46, now back at the
first I.F. frequency of 9 MHz.
C147 serves the dual function of
resonating with TlO) and serving
as the first element in a low pass
filter composed of C147 , 1104 and
C148 ,which fllters out unwanted
mixer products. R157 terminates
the filter in its required load.
PBT oscillator Ql2) is a conventional Colpitts crystal controlled
illator, with C203 and CZ04 providing the feedback capacitive divider.
and R215 form the bias network, while Rl27 is the emitter resistance.
3-6
-e
·
,,
l.

-- ~~M~!~ATIONS
S ... ,., DIVISION
t
--------,\
I.
~~
,
,"OllA
10 PIITO
P.II.
TUMIIII
+tO.!IV
+IV
PBT
OSCILLATOR
PBT SWITCHING
+IO.5V
R213
C207
PI TUNING
LSII
LINE
and C205 form a parallel re sonant collector load. The frequency of the osc-
illator is adjusted by the application of a voltage from the PASSBAND tuning
control on the front panel
through isolation resistor
R2l3, to varicap CRllO. The
range of adjustment is set
by trimmer c206, while C20?
is a bypass.
. Because the s~e freq-
uency oscillator signal is
applied to bath PBT mixers,
any signal going into the
first PBT. mixer will leave
the second on precisely the
same frequency. This is why
the PASSBAND tuning control
only affects the relative
position of the passband and
has no effect on the freq-
uency of the signal tuned in.
The direction of tuning
of the passband oscillator
must be one way for USBjCW
operation, and the opposite direction for LSB operation for the effect at
audio to remain the same. When in the LSB mode, a positive voltage is ap-
plied through CR12l on the audio baard to the base of Ql08, through limi ting
resistor R164. Simultaneously,
it is also used to turn sect-
ions Band C of switch UllO on.
Section B of U1l0 applies +10.5
volts to the upper end of the
PASSBAND tuning control Rl03A,
while section C grounds the
other end. Since QJ.08 is sat-
urated, its collector is low,
and this voltage, applied to
sections A and D of UllO, turns
them off. When in the USB or
CW modes, however, the LSB line
is low, and thus sections A and D of U1l0 are on, while sections B and C
are off. This action reverses the voltage applied to the tuning control.
Operation of the PASSBAND tuning indicator will be covered in the "Anc-
illary Circuits" section of this manual.
CWN FILTER
Signal at the second I.F. of 13.8 MHz, from the first passband tuning
mixer (QJ.08), is also coupled to the base of QJ.09. Bias is received from
the same network that supplies QJ.lO, the filter driver. QJ.09 acts as an ein-
itter follower driver for the CW narrow filter, and the required filter ter-
mination impedance is provided by R138 and R139, while C129 is a blocking
capacitor. The CW narrow filter is composed of YlOl and Yl02, with C13l and
C133 acting as coupling capacitors and C130 and C134 providing adjustments

_CUBIC
COMMUNICATIONS
S""AIfI DIVISIDN
to ~ro~erly align the filter re-
s~onse. Cl)5 acts as an out~ut
cou~ling ca~acitor, and carries
the signal to the base of Qlll.
Power for Qlll is taken from the
CWN line, and bias is ~rovided
by R14j and R146. Out~ut is
taken across emitter resistor
R147 and cou~led to the second
~assband tuning mixer Qll) th-
rough C141 and R148.
"'H
01011
CI
ï1
ZII Cl 1 Cl33 C13!!
"1311 YIt;;;I:,~
Cl! -=- J: I. --:r: fc 134
-= -=-=":'
Cl32
+-'O.llV
TOOll3
Old'
RI4
CI41
RI47
MAIN I.F. AMPLIFIER
NARROW CW
FILTER
TI04
10.llV
CI56 ~
~""""""""""-r._...-_~_C_I!!_7.r :IÇ oWo
MAIN t.F. AMPLIFIER
RIllII
FROM CI!!I
0113 c>--l
The signal from Qll), now
again at the 9 MHz I.F., is co-
u~led through C151 to the main I.F. amplifier, UlOl. This integrated cir-
cuit is composed of two am~lifier seetions, with the out~ut of the first
section developed across the R16o-LI05
load combination. C154 re sonates with
LI05, while R160 broadens the res~onse
by "swamping" the tuned circuit. C152
couples the out~ut thus develo~ed from
the first amplifier seetion of UlOl to
the second section of the same IC. Out-
~ut of the second seetion is cou~led to
push-~ull Tl04, which is resonated by
C156. C157 is a bypass. The output of
Tl04 is coupled to the product detector,
Q120. AGC control is a~plied through
voltage divider R158--R159. Overall
gain of UIOl is up to 70 dB.
PROruCT DErECTOR!AUDIO MUTE
+IV
PRODUCT DETECTOR
AND MUTE
Carrier oscillator en-
ergy is cou~led via C186 to
the base of Ql21, which for-
ms an emitter-coupled pair
with Ql20. Bias is develo~
ed by R200 and R198, acting
as a voltage divider, and
R201 and R20) serve as isol-
ating resistors, while Cl84
is a bypass. Ql20 and Ql21
act as a mixer, combining
the I.F. input from Tl04 and
the carrier oscillator sig-
nals to ree over the audio
frequency of the ineoming
signal. Out put is coupled
via C182 to an RC network
eomposed of R218 and C208,
1'1191
R 11111
1'1200
CI1I2
cillT
R202 b
'= FROM
CARRIER OSC.
CZIO TO
.....+-~-+--l r-o NOTCH
FILTER
CRIII
C201l~
"1'1"
LlHE
-8

_CUBIC
COMMUNICATIONS
SIIWAItI DIVISION
which filters out any undesired mixer products. Q124,
in series with the signal path, acts as a switch to
cut off the receiver output AF when in the transmit
condition. In that instance, the "R" line would be
low, grounding the gate of Q124 and causing it to act
as an open circuit. R2l9 and R220 provide bias volt-
age for the source and gate. Output of the AF mute
gate is then coupled via C2l0 to the base of AF ampli-
fier Q125, which provides additional gain. Bias is
conventional, while the emitter resistance is only
partially bypassed to set the gain (see the "Servicing
Hints" section of this manual for a discussion of fe-
edback amplifiers such as this). Output is taken via
C2l), while C2l4 provides a degree of high frequency
rolloff for more pleasing audio response.
+.v
A.F. PREAIIIP
RIOZ
A •
RI77
RI7lI
0-
OUT
CI45
.... -i I---4I
CI4
'
MOTCH FILTER
~: 0- ........ """"' ........ --1
NOTCH FILTER
•
Audio from Q125 is
applied to CR12) and CR-
124, which act as a lim-
iter, effectively clip-
ping off any peaks exce-
eding approximately ±O.7
volt. The R172-C14) com-
bination filters the out-
put of the clipper and
shapes the audio response. UlOlC is connected as a voltage follower, pro-
viding drive for active filter UlOlD that is the same amplitude and phase as
its input, but of a lower driving impedance.
Cl44 and R178, wi th R120A on the front panel, form the series leg of a
We in bridge, while C145, R177 and RlO2B (also on the front panel) form the
shunt leg of the same We in bridge. This bridge is inserted in the inverting
feedback loop to form a notch when combined with the normal audio frequency
applied to the non-inverting input of amplifier UlOlD. R176 and R174form a
positive feedback path to raise the"Q" of the circuit.
Aumo POWER AMPLIFIER/RECEIVER MUTE
Audio from the output of the notch
filter is applied to the high side of the
front panel volume control, and its wiper
is returned, through R127, to the input
of audio power amplifier UlO). R129 acts
in conjunction with R127 as a voltage di-
vider. Receiver mute switch Q104 is con-
nected between this input and ground, th-
rough isolating capacitor Cl17. Wh en in
the receive condition, a voltage on the
"R" line holds Q104 in the "open" eon-
dition, allowing the signal to be ampli-
fied by UlO); when in the transmi t con-
dition, the "R" line is grounded, turning
Q104 "on" and shunting the signal to gr-
"ROM
VOL. WIPER
+I 6V

OCUBIC
COMMUNICATIONS
S"".IfI DIVISION
"T"
L'"
)
ound. CIIS and R12? shape the audio response.
When in the transmit condition, and when sending CW, the sidetone audio
signal is applied to the other input of UlO); thus, the operator is able to
monitor his own sending.
CIIJ and Cl14 form an audio shaping network for more pleasing response,
and Cl12 couples the output to the speaker. ClIO and Clll are RF bypasses.
CI09 bypasses certain internal circuitry of UIOJ, while RIJO and Cl15 pro-
vide a tYJ?e of feedback path known as "bootstrap" •
AUTOMATIC GAIN CONTROL
RIII
CI041
'='
C"107
""0
CIII05
QI04
A8C IVITrM
+8V
RIOI
AGe
SET
I'ROM CIOI
AI' >-iHH-I
The audio frequency sig-
nal is coupled to the base of
QIOI via ClOl. Bias is set
by RIOI, RI02 and RIOJ, with
RIOI serving as the AGC th-
reshold adjustment. When the
audio peaks are of sufficient
amplitude, QJ.OI conducts, wh-
ich causes a current to flow
through RI05 and the D:l:!DAY
control, a variabIe resist-
anceto ground. The voltage
drop across this combination
charges capacitor CI02, with
series resistor RI06 control-
ling the charging time, and
thereby the attack time. When
the AF signal disappears, C-
102 discharges through RI06 and the RI05-DECAY control combination, thus the
setting of the control varies thedecay time of the AcC.
The voltage across CI02 is applied to the non-inverting input of ampli-
fier UlOlA. Provided the output of UlOIA is greater than any reverse bias
to CRIOI supplied through CRIOJ by the I.F. GAIN control, the output of.U-
IOIA is applied to the AGC line through CRI06, and to the S meter through
calibration control RIIO and voltage dropping diodes CRI04 and CRI05. RIO?,
RIOS and RI09 establish a reference level and the gain of UlOlA.
When in the transmit condition, the "T" line goes high, and applies a
voltage through CRIOS to the inverting input of UlOlA, causing its output to
go low and remain there so long as the "T" line remains high, thus disabling
the amplifier. This ensures that the S meter is disabled in transmit. This
same voltage is applied, through CRIO?, to the AGC line to force maximum at-
tenuation of the AGC PIN diode in the IF amplifier chain, and to cut off the
I.F. integrated circuit amplifier, UI Ol ,on the exciter board. This ensures
that no signal is present in the AGC loop during transmit and full gain is
available when switched back to receive.

- ~~M~~~ATIONB
SIMAIfI DIVISION
Microphone Preamp1ifier •.•••• ~ •••••••••• 4-1
Speech Processor •••••••••••••••••••••••• 4-1
Modulation Amplifier •••••••••••••••••••• 4-l
Ba1anced Modulator •••••••••••••••••••••• 4-2
First I.F. Amp1ifier •••••••••••••••••••• 4-2
Noise Blanker Gate •••••••••••••••••••••• 4-2
Filter Buffer, Filter ••••••••••••••••••• 4-3
Transmi tMixer .... - ••.•••••••.•....••••. .4-:3
Preselector
Input switching •••••••••••••••••••••• 4-4
Bandpass Filters ••••••••••••••••••••• 4-4
Amplifiers ••••••••••••••••••••••••••• 4-5
Power Amplifier
Predri ver ...•....••.. 1- •••••••••••••• •4-6
Driver Amplifiers •••••••••••••••••••• 4-6
Output Amplifiers •••••••••••••••••••• 4-7
P.A. Bias Contro1 •••••••••••••••••••• 4-7
Low Pass Filters •••••••••••••••••••••••• 4-7