QEI 691 User manual

(609) 728·2020
CORPORATI N
ONE AIRPORT DRIVE, P. O. BOX 0 .. WILLIAMSTOWN, N. J. 08094
FM MODULATION MONITOR/TEST SET
MODEL 691
INSTRUCTION MANUAL

INFORMATION FOR ION -02, DUAL 67 & 92 KHz SCA,
IS LOCATED IN THE APPENDIX IS MANUAL.

SECTION 1
GENERAL INFORMATION
1-1 DESCRIPTION
The QEI Model 691 Modul on Monitor/Test ( Type Approval
Number 3-244 ) is an all id Modulation Man; designed to
meet or exceed the Communication Commission requirements for
measuring the modul on cs of FM transmitters having a
frequency range of 88.1MHz .9MHz both at the transmitter and aff-
air.
The 1 is in a 1O~" X 19" rack mount. All
controls are located on the front panel. AC Power, RF Inpu
Outputs are located on the rear panel.
1
ELECTRICAL
FICATIONS
RF Frequency Range .................. 88.1 - 107.9r1Hz
(Thumbwheel s
RF rnput (to guarantee 66dB SIN in a 30KHz Bandwidth)
An tenna ... . . . . . . . . . . . . . . . . . . . . .. 3mv 200mv
Signal ........................ 2mw 50W (depending on external
load)
Total Modulation Display
~iodulati on Meter
Accuracy ........................ +2% entire range
Frequency .............. O.2d8 30Hz - 75KHz
Range ........................... 0-133% (-20d8 to +2dB)
111s cs .....•................ per FCC regulations
rs
.......................... "'.11> •••••
Ace u racy,. , ..... """. " .. " .. _" .... "...... " ... ""
Peak Counter
Poi
Time .. ". "" II .. , " • '" , 11 '" » " .. It '" .... II • '" ... l1li .. I (I
0-199% in 1% increments
+ 1%
100% + 1%
1 minute + 1 sec.
Distortion .......................... 0.05% THD or IMO
SIN • .••.••••.•.•••••••••••••••.••.•• better than {with de-emp}
in a 30KHz Bandwidth
Test Displays (2)
Me ter Accu ra cy .................. .
Peak Indicator Ac .......... .
Meter Range ..................... .
Pilot & SCA Injection
better than
+ 2% entire range
+" 1%
to -75dB (autoraryging)
~ 0.5% (6% to 12%) ~

Separation
L
into R or R into L .......... 55db
Crosstalk
Main into Sub ...•..
Sub into Main .••.•
SCA in Sub or Main ..
Pilot into Sub or Main.
Monitoring Modes
1)
2)
Main
3}
Pil level
4)
38KHz
5)
FM/S/N
6) SeA Inj.
narrow
7)
SCA Inj.
wi
Distortion (
THD • • • .
IMD . . . . . .
(4KHz dev.)
Outputs
Right
Scope
Frequency .
or ght)
Spectrum Analyzer Output
X Hori zonta1. . . . . .
YVertical ...... .
1 MECHANICAL SPECIFICATIONS
Dimensions.
Weight ....
Ambient Operating Temp.
• 65db
. 65db
. . . 70 db
70 db
Right
Sub
Phase Cal.
Gen. Phase
AM SIN
Main
SCA Mod.
0.05%
· 0.1% (SMPTE}
· 1% (50Hz to 5KHz) (150us de-emp)
+10 dbm bal. and Hi-z
· +10 dbm bal. and Hi-z
IVpp
X.D, I.F. Pilot, SCA (TTL)
· 4Vpp
0.5V/lOdb
• (lOt"H ) x (l9
uW ) x
(I2
11
D )
(26.68cm) x (48.29cm) x (30.Scm)
16 1
· 3rF of
aoc to 60°C

1-4 INSTRUMENT IDENTIFICATION
This unit is identified by a Model and Serial Number located on the rear panel.
All correspondence to your sales representative or the factory in regard to the
unit should reference the
complete Model and Serial Numbers.
1-5 OPTIONS
(01) SCA Monitor option (67KHz) consists of the plug 1n board assembly A6
(02) SCA Monitor option (special frequency) (not FCC Type Approved)
(03) CerR Specifications (not FCC Type Approved)

2-1 INITIAL INSPECTION
SECTION 2
INSTALLATION
ChecK the shipping carton for external damage. If the carton exhibits evidence
of abuse in handling (holes, broken corners, etc.) ask the carrier agent to be
present when the unit is unpacked. Carefully unpack the unit and inspect all
equipment for physical damage. Immediately after unpacking any bent or broken
parts, or scratches should be noted. Keep all packing material for proof of
damage claim or for possible future use.
2 PREPARATION FOR USE
The unit is designed to be mounted in a standard 19" rack. Air space should
be provided above and below the unit so that heat generated by the circuitry
may be dissipated. Additional co01in9 may required if the unit is placed
above high heat generating equisment in order to keep the ambient temperature
below the maximum specified (50 C).
Mount the unit to the rack using #10 caun
ink screws and finishing washers.
The unit requires a l05-125V ngle phase, SO/60Hz power source or a 220-250V
single phase. SO/60Hz power source. The identification plate on the back
panel
shows for which power source the unit is wired. See Section 5-7 for
information on changing
MONITOR CONNECTIONS
1. Connect the antenna supplied to monitor ANT connector Jl1 if off air
operation is desired.
2. Connect a dummy load 1a enough to handle the RF input to DUMMY LOAD
connector J9. A ~ watt termination is supplied. The input signal sampler
will handle up to 50 watts with an adequate external dummy load. thus
allowing
direct measurement of exciters and low power transmitters.
DO NOT OPERATE THIS EQUIPMENT WITHOUT AN ADEQUATE DUMMV LOAD INSTALL
3. Connect the RF sample to RF IN connector J10.
4.
TB1-4 and TSI are 600 ohm balanced left audio output.
5. TB1-6 and TB 7 are 600 ohm balanced right audio output.
6. TSl is 600 ohm unbalanced SeA audio (ref. to gnd.)

2-4 REPACKING FOR SHIPMENT
NOTE: WARRANTY MAY VOID IF UN IS NOT RETURNED IN ORIGINAL PACKING.
NOTE: Before returning a unit for repair or calibration, contact the ry
or your author; representative for Return Authorization. Attach a tag
showing owner's name and address. A ption of the service required
should also
be included. it must be shipped prepaid and insured for full
value. USE THE ORIGINAL SHIPPING CARTON AND PACKING MATERIAL FOR RE-SHIPMENT.

SECTION 3
OPERATION
3-1 OPERATOR CONTROLS AND INDICATORS (FRONT PANEL)
1. POWER Switch and led A1S1 and AleRl apply line power to unit.
2. CARRIER FREQUENCY thumbwheel AIS2 sets unit on desired frequency.
3. L.O. UNLOCK 1 A1CR2
Led lights if local 11ator ;s unlocked or reference is lost.
4. RF LEVEL leds A1CR3 (Hi), AICR4 (LO), A (OK)
a. Ale (OK) will light and AICR4 (LO) will
is sufficient RF input to allow accurate modulation and
measurements. This level will normally be obtained wi
supplied wi in the 70dBu contour.
go out when there
signal to noise
the antenna
b. AICR3 (Hi) will light if an excessive RF sample is applied.
Reduce the RF LEVEL t on rear panel until AICR3 extinguishes. A1CR5 (OK)
will remain lit with Hi Rf level since all required monitor functions will
in specified on. However. AM Signal to Noise wi1l not accurate be-
cause of saturation the IF amplifier. In addition, when AICR3 (Hi) is
lit. the input mixer is being protected by an input clipper.
5. MUTE Switch AlS3
a. With MUTE switch in ON ition unit will mute all signals
below RF LEVEL OK hold.
6. COMP Jack AIJI provides a 6Vpp wideband compos; signal.
7. DE-EMP AUDIO ck AIJ2 prov; a 6V
p
p' @ 400Hz signal with 75usec
de-emphasis.
NOTE: This signal is filterea to remove 19KHz.
8. TOTAL MODULATION Displays (Yellow)
a. AIM1 in conjunction with MOD METER switch AlS4A prov;
total modula on (main, sub and SCA) i ication with semi-peak ballistics
switchable to POS or NEG.
b, PEAK MOO thumbwheel AlS5 and lamp AIDSl provide a total modula-
t'ion peak indicator independent of polarity and settable in 1% increments
from 0 to 199%. This flasher will light from 2 to 4 seconds each me a
peak is detected.
c. 100% PEAKS PER MINUTE Display AIDS2 and RESET/OfF Switch A1S6
provide a count of 5ms 100% peaks. The display flashes at a count of 10,
has a maximum count of 19 and resets automatically each minute. RESET over-
ri the automatic reset function and OFF extinguishes the display. This
indication is in to moni modula on peaks for Automatic Transmitter
tems (ATS) as ned by the FCC in the ATS rules.

d. CAL pushbutton AlS7 provides a modulation calibrate
.;~ . signal. The frequency this signal is 32KHz. Section 5 for further
information. NOTE: lO UNLOCK led must light when CAL is depressed.
9. Display (Vector and Spectrum Analyzer)
NOTE: To use these features of the 691 res an oscilloscope
wi X and V DC Coupled inputs. The bandwidth of scope need only be a
few hundred kTTohertz but it must DC Coupled on both X and Y inputs.
a. Connect VERT (AIJ3) Scope Y input. Connect HORIZ (AIJ4)
to
Scope Xinput. Set both inputs to DC coupled, 0.5 vol /div.
b. To ew Stereo Vector pattern, depress VECTOR on AlS4B.
Mono modulation will ve a vertical line. Any deviation from vertical in-
dicates that the on mono balance is incorrect.
c. To use Spectrum Analyzer , depress NARROW pushbutton
on AIS4B. Adjust horiz. (X) gain get full width baseline. Adjust
vert (V) gain to O.5/div. Dis ay will centered on de-
termined
by CARRIER FREQUENCY swi and will be approximately and
10dS/div. Depressing WIDE pushbutton will change dispersion to approximately
+350KHz. NOTE: WIDE position will cause TOTAL MODULATION displ to pin
- and peak flasher if is OFF.
10. PILOT PRESENT indicator A1DS3 and 0AOJ AIR! indicate the presence
of the pilot tone and provide monitor calibration in conjunction
with 0 posi
on of CHANNEL B DISPLAY SELECT. lot 0 ADJ AIRl is set
for a null on CHANNEL B meter. This adjustment is accurate even with modu-
lation appli
11. SeA PRESENT indicator AIDS4 indicates the presence of SCA.
DEV switch A1S9 may be set to cause CHANNEL B SCA MOD spl to indica
100% at ei 4KHz or 6KHz dev; on.
12.
FREQ Jack AIJ5 and switch AIS8 provide a conveni output for an
external counter to read station frequency, pilot frequency or SeA frequency.
To read station requires a counter capable lO.7MHz. First con-
the counter to
XO jack on the rear panel. If the X.D. ;s not exactly
8.000000MHz, adjust piston trimmer on the monitor A2 as y until it
See Section 5 details. Now the counter to A1J5 and place
to
IF position. counter should 1O.7MHz. If it lower.
station frequency is higher by the same number of hertz. Conversely. if
reads hi her, the s ion frequency is lower. NOTE: .=.B.=.e--=...::..:....:;:.-::..:..-..,:=

13. OUTPUT SELECT Switch A1SIO. AUDIO' Jack AIJ6 and SCOPE Jack A1J7
provide distortion measuring outputs and scope observation output. Switch
AISIO in FT/CHAN A position provides left deemphasized audio with a cutoff
frequency of 15KHz for 5 distortion measurements at AIJ6 and whatever
is displayed on the CHANNEL Ameter at AIJ7 for scope observation. When
AISIO is in RIGHT/CHAN B position, right audio is provided at AIJ6 and
Channel B signal appears at AIJ7.
14. SeA Audio Jack AIJ8 provides 150usec deemphasized 5KHz bandwidth
SeA audio for distortion measurements.
15. TEST DISPLAYS (CHANNEL A - green) (CHANNEL B - blue) and DISPLAY
SELECT switch AISII
a. DISPLAY SELECT switch controls the s;gna1 componen to be
displayed.
b. Meters AIM2A and A1M2B in conjunction with +/- switches
AlS13A and AlS13B, MOD; HOLD: AUTO switches AlS14A and AlS14B and RANGE
(-dB) readouts AIDS5A and AIDS5B provi two metering displays with a
range of 0 to 133% with FCC ballistics (MOD posi on) or -70dB to +3dB
with semi VU ballistics (AUTO or HOLD posi on). These displays may be
switched to + or - indications and may be deemphasized by pushbuttons
A2S15A or AlS15B. NOTE: FM and AM S/N are automatically deemphasized.
c.
PEAK thumbwheels AlS12A and A1S12B and leds A1CR6A and A1CR6B
provide a peak indication of the corresponding meter display settable in
incremen
from 0 to 199%.
OPERATOR CONTROL AND CONNECTIONS (REAR PANEL)
2. RF INPUT Jack AIJIO -Transmitter RF sample connects to this jack.
3. CARRI LEVEL Control AIR2 -This control is used to reduce RF
Input below RF HI threshold.
4. ANT Jack AIJll - 75 ohm FM Antenna to this jack.
5. X.O. OUT Jack AIJ12 - 8MHz sample from crys 1 reference oscillator
is available this jack for measurement purposes.
6. S.A. CENTER Control A1R3 -Control used to center Spectrum Analyzer
splay.

7. COMPOSITE EXT INPUT AIJ13 -s input allows a compos; signal
~. to be appli the Stereo and SeA circui the monitor bypas-
sing the
RF
8. COMPOSITE EXT
level.
Control AIR4 -Sets external composi signal
9. COMPOSITE Switch AIS16 -This tch must be in INT position to
use
RF demodulator. In EXT position signal appli to COMPOSITE EXT INPUT
AIJ13 is fed to stereo and SCA circuits.
3-3 MONAURAL MEASUREMENTS
1. Total Modulation
the
FREQUENCY thumbwheel the desired frequency and
MUTE switch to ON. Verify that L.O. UNLOCK led ;s out and that RF LEVEL
OK 1 is lit. Allow a few for monitor to lize on
frequency selected. Adjust MOD thumbwheel to the desired 1
The amber PEAK MOD lamp will ash for 2 4 seconds each time the modu-
lation exceeds preset PEAK MOD level in ther a positive or nega ve
rection. TOTAL MODULATION meter responds to total modulation with
FCC specifi ballistics and may be switched to read either positive or
negative modul on with the MOO METER POS or NEG pushbuttons.
Total
Peak Mod Flasher and Total Modulation Meter will
only agree if the transmitter is modulated by a low di
tion sine wave. Any distortion will cause positive nega-
tive assymmetry approximately double the amount of the dis-
tortion in percent. that the flasher reads
highest polarity and that meter reads the sel
polarity. The difference in read; with program material
is due to many factors such as the of audio dynamic
range compression. transmitter overshoot, program assymmetry,
etc.
The 100% PEAKS PER MINUTE counts number of positive or negative
ks occurin within one minute. This counter was igned to show
campI ance with ATS rules. Therefore, it counts 5 millisecond peaks
as per FCC rules .342(b)3. However, the required PEAK MOO flasher must
remain lit for 2 4 seconds time it triggers FCC rules 73. (D)4i.
This
means that it is possi e to get many ATS 5 mil isecond peaks during one
ash of the PEAK MOD flas r. Since ATS rules allow 10 (ten) 100% 5 milli-
second peaks minute, the readout at 10 and has a maximum count of
19. It cally at one minu intervals may be man ly reset
or turned off with its ated switch.

2. Mono Distortion
Approximately 6V @ 100% @ 400Hz is available for connection to
a
high Z distortion me~gr at the DE EMP AUDIO jack. This output is
deemphasized 75usec and ;s fil to remove 19KHz.
3. FM Signal to Noise / AM Signal to Noise
Remove modulation from the transmitter. Depress FM SIN - AM SIN
OISPLAY SELECT pushbutton. Place CHANNEL A and CHANNEL B METER MOD/HOLDI
AUTO switches in AUTO. FM Signal to Noise will displayed on CHANNEL A
meter
and AM Signal to Noise will be displayed on CHANNEL B meter. The
reading will be the aigebraic sum of the METER RANGE (-dB) readout and
the associated meter. Note that FM SIN is automatically measured with
deemp in a 50Hz to 15KHz bandwidth. If it is desired to check
for
FM noise below 50Hz, e.g. blower vibration, depress DISPLAY SELECT
MAIN-SUB and read CHANNEL Awhile holding CHANNEL A METER EMP - FLAT
pushbutton depressed. Any difference in the noise readings indicates
noise with a frequency component below 50Hz. AM SIN is automatically
measured with 75usec
deemp and is accurate as long as the RF LEVEL HI
led is out and RF LEVEL OK led is lit. The residual noise be ob-
served with a scope connected
to SCOPE jack. The OUTPUT switch'
is then used to route either Channel A or Channel B to the scope.
3-4
STEREO MEASUREMENTS
1. Left and Right Channel Modulation
Depress
DISPLAY ECT LEFT GHT pushbutton and place METER MOD/
HOLD/AUTO switches in MOD posi'tion. CHANNEL A meter will indicate
left channel modul ion and CHANNEL B meter will indicate right channel
modulation with
FCC spec; ed semi balli cs.
A fully modulated left or right stereo signal will indicate 90%.
rf pi' is removed, both meters will indicate the same as the
TOTAL MODULATION meter.
If MOD/HOLD/AUTO switches are placed in HOLD position, the ballistics change
to semi-VU and the RANGE (-dB) readouts will illuminate. If the METER DE EMP
pushbutton is then depressed, the meter will give an approximate indication
of the loudness ived at the output of a receiver.
2. Separation
Depress
DISPLAY FT-RIGHT pushbutton and place METER MOD/HOLD/
AUTO switches in AUTO position. Apply a fully modulated left or right signal
to the
transmitter. The fully modulated channel should read 90% (-ldS). The
unmodulated channel will autorange to ve the separation reading. (Algebraic
sum of the METER RANGE (-dB) and its associated meter -ldB.) NOTE: Be sure
of monitor 0 calibration before attempting separation measurements. See 3.4.7.

3. and Right Signal to Noise
Depress
OISPLAY LEeT LEFT-RIGHT pushbutton and place METER MODI
HOLD/AUTO switches in AUTO position. Remove 1 and right modulation
from transmitter but do not remove pilot. Depress METER DE push-
Meters
wi11 autorange ve signal to noise readings.
4. left and Right Distortion
High; deemphasi audio is available at LEFT/RIGHT
AUDIO jack for connection to a distortion t set. The signal is
switched between left and right by the OUTPUT SELECT switch.
5. Main Channel (L=+R) and Subchannel (l=-R) Modul on
Depress OISPLAY MAIN-SUB pushbutton and place METER MOD/HOLD/
AUTO swi in MOD ition. A fully modulated signal will read
90% on CHANNEL Ameter
signal
will read 90% on
o on CHANNEL Bmeter. A fully modul L=-R
CHANNEL Bmeter and 0 on CHANNEL Ameter.
6.
talk (Main into Sub and Sub into Main)
s DISPLAY MAIN-SUB pushbutton and ace METER MOO/HOLD/
AUTO in AUTO position. A ly·modulated L=+R or signal will
indica 90% (-IdB) on i respective meter. The other meter will
to give the crosstalk reading. (Al c sum of METER RANGE (-dB) and its
as meter - . )
7. Pilot Injec on and Monitor Phase ibration
Depress DISPLAY SELECT prLOT - ~ CAL pushbutton and ace METER
MOD/HOLD/AUTO swi on. Pilot injection is then read on
lOT scale PI lamp will light at
approximately pilot inj Calibration ;s accompli
by n9 PILOT0 CAL control for a null on CHANNEL B meter. Phase Calibra-
tion may be accomplished accurately while transmitter is n9 modul
8. 38KHz Suppression
Depress
DISPLAY 38KHz - GEN 0 pushbutton and place METER MODI
in AUTO position. Modulate the transmitter with a -R
signal 5KHz and 15KHz. CHANNEL A meter will autorange to ve
38KHz suppression reading.
9. Stereo Genera
e
Check monitor phase calibration according
modulation as
in 3-4-8 above. Adjust stereo
minimum indication on CHANNEL Bmeter. This
tor without an 110scope.
to 3.4.7. Set monitor and
phase control for
allows ng genera-

seA MEASUREMENTS
NOTE
This monitor is designed
for use with a 67KHz
as used with stereo.
1. SeA Injection (Unmodulated)
and approved only
and 10% SeA injection
Depress DISPLAY SELECT SCA INJ NARROW-MAIN pushbutton and place METER
MOD/HOLD/AUTO switches in MOO position. CHANNEL Ameter wil1 read SeA in-
jection on the PILOT scale through an FCC specified narrow filter. The SCA
must unmodulated for an accurate reading. The SCA PRESENT lamp will light
at approximately injection. Main channel 0 - 15KHz modulation will be dis
played on the CHANNEL B meter.
2. SeA Injection {Modulated}
Depress DISPLAV SeA INJ WIDE-seA MOO pushbutton and place
METER MOD/HOLD/AUTO switches in MOD position. CHANNEL Ameter will read SeA
Injec on on the PILOT scale through a wide filter. This lter allows in-
on to be monitored while modulating the SCA.
3. SeA Modulation
Set monitor up as in 3-5-2 above. Place SCA OEV switch in 4KHz or
6KHz position as desired. This sets the deviation for 100%. CHANNEL B
meter will indi
SeA Modulation with FCC semi-peak ballistics.
4. SeA Distortion
High impedance 150usec deemphasized SeA audio is available at the
SeA AUDIO jack for connection to a distortion test set.
5. SCA Signal to Noise
Depress DISPLAY SELECT SeA INJ WIDE-seA MOD pushbutton and place
CHANNEL B METER MOD/HOLD/AUTO switch in AUTO position. Modulated the
mi th a unmodulated SeA. Depress CHANNEL B METER DE EMP push-
button.
Meter will autorange to give noise reading. Reading will be made
with 150usec deemphasis.

4-1 GENERAL
SECTION 4
THEORY OF OPERATION
The monitor is basically a special; FM superhet ver. It has
been s ifically signed to operate in a high RF environment and as such
does not an RF preamplifier. It s also been designed with a wide
IF filter in to meet FCC requiremen for FM modul on monitors.
Because
of these ints it is neither as sensitive nor as selective as
a normal FM receiver. However, it will operate in close proximity to antenna
farms
and mas r antennas i rmodulation and overload problems
normally
encoun red in these areas.
Un1i
691 is
other monitors/RF ampli er systems, the signal path in the
same whether the monitor;s ven from transmitter or 0
air «
transmi
dation
within
only
difference is a -40dB signal sampler when driven from the
input
(RF IN) port. This means that is no signal degra-
used off-air above the mute level. This 1 is set for use
70dBu contour with antenna prov;
Refer
to Block Diagram 12001. RF signal ;s fed to either the Antenna
or
RF inputs. The si 1 then passes through voltage tuned i
on board (AI3) then to A4 receiver assembly. The output of e
locked
1st Local Oscillator is also fed to A4 assembly producing a 10.
IF. The L.O. phase lock loop circuitry is 1 on the A2 assembly. The
IF is fil red, demodulated, and resulting composite signal is
ampli ed and fed the various filtering, stereo and SeA demodulation and
metering circuitry required. A portion of 10.7MHz IF is also fed to a
mixer a10ng a swept 2nd L.O. ope i at 10.255MHz + The re-
sulting 455KHz + is filtered by a ceramic filter. to a logarithmic
amplifier, demodul and used to provide a spectrum analyzer presentation
on an x-v oscillos
4-2 DETAIL CIRCUIT DESCRIPTION
1. Al (Chassis) Assembly
The sis assembly contains the power supplies
fil jIst L.O., meters, indi and controls.
regula by three terminal
2. A2 (PLL and Total Oriver)
Assembly
• -12V. +5V),
supplies are
The output of a hi lity crystal oscillator {VI, Q
is divided down to A sample of the L.O. is fed to Q9
to a programmmable divider. The CARRIER FREQUENCY thumbwheel p
di so that when the L.O. is lO.7MHz the thumbwheel sett
the divider output is 5KHz. The reference signal and the programmable sig-
nal are compared and the resultant error voltage is fil by
active filter U U16 and then fed to AfC port of the t L.a. U12
. is used to light L.O. UNLOCK led if lock or reference is 1 Ull ;s
used to genera KHz pulse for the calibrate function.

U17 and U18 and the Total PEAK MOD thumbwheel form a precls10n positive
and negative reference for the modulation peak comparators U20. RS3 and R86
provide reference for the 100% PEAKS PER MINUTE comparators. Composite signal
from the A4 assembly is also fed to these comparators.
The outputs of these comparators are fed to one shots of 2 to 4 seconds
in the case
of PEAK MOD and 5 milliseconds in the case of the 100% PEAKS PER
MINUTE. The 100% PPM one shot drives a counter made up U22. U23 and U24.
This counter is reset every minute by a pulse derived from the A3 assembly.
Composi signal is also fed through the TOTAL METER POS and NEG
hes to the total meter driver circuit. U13, U14 and associated circuitry.
3. A3 (Dual Average Voltmeter) ly
This board contains
two identical voltmeter circuits, one for Channel A
Display, one for Channel B Di lay plus the reset generator (U10) and decoder
driver (Ul1. U12, U13) for the 100% PEAKS PER MINUTE display.
Channel A designators are in units; Channel B designators are in hundreds.
Al and U1 along with their associated PEAK thumbwheel are used drive the
TEST DISPLAY PEAK led. Signal components selected by the DISPLAY SELECT pus
buttons and the METER +J- switch are amplified or inverted by U2 and fed to a
combination attenuator-amplifier. This combina on provi gain in lOdB
steps from 0 dB to 50 dB. The action is as follows:
RANGE
AMP
OdB -30dB
+30dB
-lOdB
-20dS
+30dB
-20dB
-lOdB
+30dB
-30dB
OdB
+30dB
-40dB -lOdB
+50dB
-50dB OdB
+50dB
The range changes are accomplished by the outputs of up-down counter
U6 being used to clamp the appropriate resistors to ground through U3. A
sample of the attenuator-amplifier output is fed to comparator US. The
output of U8 in conjunction with gates U5, U6, and U7 then drives U6 up or
down to the required ran
The output of the attenuator-ampli r is then peak detected by Q7
and meter driver U9. Q9 is used to change ballistics from FCC to
VU as required.
4. A4 (Receiver) Assembly
Q1 and associated circuitry buffer and filter the output of the 1st
L.O. (fc + lO.7MHz). This signal and the incoming RF are mixed in balanced
,~
'---.

mixer ZI to produce the 10. IF. This IF signal ;s amplified by Ul.
filtered and applied to U2 which is IF Amplifier and Demodulator
System. The demodulated compos; U2 is amplified by Q4 and
and
filtered by a low overshoot, ted low pass filter.
Either the output of this filter or input from the rear
panel ;s supplied to composite driver ampli er Q8, Q9, QIO~ Qll and
012. The output of this amplifier is 6V
pp
@ 100% and is used to drive
the stereo and SeA monitoring circui .
Q6 and lter C54, l16 C55 convert a 32KHz pulse
assembly to a
32KHz sine wave which is used to FM a 10.7MHz
(Q7 and associated circuitry) when the CAL pushbutton is
Signal is coupl to IF amplifier and used to provide
calibrate signal.
The RF signal level vol at U2 pin 13 is fed to voltage comparator
rcuit U3. of this Ie are used to mute the monitor and so
drive the
RF . and OK 1
The lO.7MHz si 1 from the IF filter FLI is also fed to mixer Z2
through bu it ;s mixed with the output of 2nd L.O. Q13
and 014. This L.O. is frequency swept by a sawtooth generator made up
of CRI4, Q16 a U6. e output of the sawtooth generator is also used
to sweep the t L.O. in ECTRUM ANALYZER WIDE mode through 015. The
455KHz ou t of mixer ;s fed through buffer 017 and Q18 to the
spectrum analyzer
filter and logarithmic amplifier U4 and associated
circuitry. The output of the log amp is AM demodul and fed through
ive filter U5 to the SCOPE VERT jack and AM Noise measurement
circuit.
5. (Stereo Demodulator) Assembly
Composite signal is fed to Ql which drives pilot filter. The
19KHz is squared by U3 after passing through the se ust
t
composed of Q3, 04 and the front panel PILOT 0 CAL control. The
19KHz re wave is used to lock PLL U4. The output U4 is nominally
190KHz. This signal is divided down to provide square waves of @
00, 38KHz @ 180
0;
38KHz @ 90
0
and 19KHz @ 90
0. These
signals are us
demodulated le and and also to provide GEN 0 calibration and
o calibration signals. demodulation is accomplished by c
Q10 and Ql1 and the resul 1 and right signals are amplifi
through
Q17. The output amplifiers is filtered and u to
the DISPLAY also audio output amplifiers U10. U13
Q19 through 022. and audio is added in U1I to produce
vertical channel for the and subtracted in U12 to
the horizontal channel splay.
Choppers 07 and 08 are
composite signal. The action
PILOT 0 null indication.
are wave at 90
0 along with
choppers
and U2 produces the

Transistor Q18 is used to couple 38KHz @ 90
0
into the Subchannel
filter to produce the GEN 0 indication.
CRI. CR2. Ul and Q6 provide the Pilot Present Lamp threshold detect
functions.
6.
A6 (SeA) Assembly
Compos; signal is buffered by 01 and fed to the dual 67KHz
lter. One section of this filter has a bandwidth approximately 1KHz
and fulfills the FCC specification for exact measurement of SeA injection.
The output of this filter ion is buffered by Q2 and fed to the DISPLAY
EeT switch. The other section of this filter has a wide bandwidth to
allow
injection measurements under modulation and also to prevent unwanted
composite signal components from reaching the SCA demodulator. U2 is a
phase locked loop demodulator.
The audio output is buffered by 06~ filtered
and ampl; ed by Ul and U4. changes the 100% deviation point from 4KHz
to 6KHz depending upon the front panel SeA DEV switch.
U3 determines SCA presence and also drives the SeA frequency output.
07 mutes SeA audio if the SeA is lost. Q8 and Q9 drive the SeA PRESENT
lamp.
7. All (Display Select Switch) Assembly
This seven station pushbutton selects the signal component to
displayed.
U1 and associated circuitry form a high pass active filter
with a low frequency cutoff of 50Hz used the FM SIN position.
Ll is a 19KHz fil that smoothes the PILOT 0 CAL null indication.

,r-- ..
ION 5
ALIGNMENT AND TROUBLESHOOTING
5-1 EQUIPMENT REQUIRED BUT NOT SUPPLIED
1. Oscilloscope, DC coupled, triggered, dual trace, horizontal input
mi n. 10 MH z BIN.
2. gital Voltmeter
3. Audio Generator
4. Frequency Counter
5. S Genera tor
6. SeA Generator
7. FM Signal Generator with Cali
RF Attenuator
8. Distortion Anal
9. Assorted les and hand
tools.
NOTE: DO NOT ATTEMPT TROUBLESHOOTING AND ALIGNMENT OF THIS UNIT WITHOUT
ADEQUATE TOOLS AND EQUIPMENT.
Before starting al ignment of this unit. veri that the three supply
volta are present and correct.
5-2 PLL AND TOTAL ER ALIGNMENT (A2 sembly)
1. Place MOD PEAK Thumbwheel (Al ) to 100.
2. Measure vol
A2U17
(TP1), this voltage should be
+
.OOV -.lSV
3. Measure voltage at A2U18-6 ( ). Adjust A2R69 until this volta
has the same magnitude but opposite pol of s (2)
4.
Measure tage on center arm of A2R83. Adjust A2R83 un
1 its
vol
is
30mv hi than
that in step
(2) (
.03V).
5. voltage on center arm of A2R86. Adjust A2R86 until its
voltage
is 30mv lower than that in step
5-2 (3) (-3.03V).
6. s NEG button on A1S4A.
7. Adjust
A2Rl until TOTAL MOD meter
(AIM1)
is
8. Apply a 400 Hz, 4Vp-p sine wave to COMP IN (AIJ13).

9. Place INT-EXT switch (AlS16) in EXT
ion.
10. Adjust COMP (AIR4) until MOD PEAK lamp (AIDSl) just
1i gh 100%.
11. Turn PPM readout switch (A1S6) to on. PPM should
12.
13.
14.
15.
.
"001i. Set MOD PEAK thumbwheel to 101%. Increase audio
slightly, PPM readout should count to "19
11
before MOD PEAK
lamp ligh at 101%.
Set audio level until MOD PEAK lamp just lights
at 100%.
Adjust
until TOTAL MOD meter
(AIM!) reads 100%.
Depress POS button on AlS4A.
Adjust A2RI04 until TOTAL MOD
(A1Ml) reads 100%.
Connect a frequency counter to X.O. OUT (AIJ12).
. Adjust
A2C16 un 1 the frequency is 8.000000 MHz.
NOTE: This will
indi L.a.
exactly 10.7 MHz above the
CARRIER FREQ. thurnbwheel (AlS2).
NOTE: crystal in the 691 Modul on Monitor is a
high a6curacy crystal with stability of 2.5 PPM from
a - 60 C.
DUAL AVERAGE VOLTMETER ALIGNMENT (A3 Assembly)
1. Calibrate PLL and Total Meter (Section 5-2)
2. Preliminary set up:
a. Place thurnbwheels AlS12A and A 12B to 100%.
b. Place +,- switches (AlS13A and A 1 in - position.
c. Place MOD-HOLD-AUTO switches (AlS14A and AlS14B) in MOD Position
d. Depress MAIN,
button on DISPLAY SECT switch (AlS11).
3. Remove audio i
from the monitor.
4. Adjust
A3R74 until CH.A meter (AIM2A) zeroes.
5. ust A3R174 until CH.B meter (AU~2B) zeroes.
6.
Apply 400 Hz audio input until MOD PEAK lamp ( OSl) just
ligh at 100%.
7. Adjust MAIN lter control (AIR15) until CH.A PEAK led just 1;