QEI 691 User manual

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QEI
MODEL
691
MODULATION
MONITOR

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SECTION 1
. GENERAL INFORMATION
1-1 DESCRIPTION
Th e QEI Model 691 Modulation Monitor/Test Set (FCC -· Type Approval
Number 3- 244 ) is an all solid state Modulation Mon1tor de~igned to
meet or exce~d the Federal Coli111un ication Commission requirements • for
measuring the modulation characteristics of FM transmitters having a
frequency range
of 88. lMHz to 107 : 9MHz both at .the -: transmitter . and off-
air. ·
The 691 is manufactured in~ 10 ½" X 19
11
rack mount. All operator
controls are located
on the front panel. AC Power, RF Inputs and Monitor
Outputs are located
on the rear panel. ·
1-2
ELECTRICAL SPECIFICATIONS
RF Frequency Range ..... . ..... . .• .... 88 .1 - 107.9MHz
(Thumbwheel selected)
RF Input (to . .g.!)arantee 66dB S/N .in a 30KHz Bandwidth)
Ant ... . ....... . .. . ... .... .. :. . .. .. 3mv to 200mv .
Sig
Sample ................... ·: .... 2mw to 50W (depending on external ·
load)
Total Modulation Display
Modulation
Meter
Accuracy .... . .........• .. . .. .... +2 % entire range
Frequency Response .... . .. ... . ... 0.2dB 30Hz - 75KHz
Range .... ......... . ..•. .•..... .. 0-133% (-20dB to +2d B)
Ballistics ......... .. ........ . .. per FCC regulations
Peak Indicators .
f
Range .. : ..... J. .................... 0-199%in 1%increments
Accuracy . .... :. . . .. .. . . .. . .. . . . . .. + 1%
Peak Counter
Set Point
...... . ........ . ...... .. . 1 00 %+ 1%
Ti me . .. . ... . . . .. . . .. . .. . .. . .; . . .. . 1 mi nute + 1 sec.
Distortion
............ . .... . ... .... • 0.05% TH D or IMO
S/N .. .•............•....• . ..... . ....
I
Test Displays (2)
better than 75dB (with 75usec de-emp)
better than 66dB in a 30KHz Bandwidth
Meter Accuracy ...• . ..... . . ...... • + 2% entire range
Peak Indicator Accuracy .... ... .•• . + 1%
Meter Range. . ..•. . . . .. . . . . •.. . . . . 1 33 %to -75dB (autorangi ng)
Pilot & SCA Injection Accµracy ... :!:_ 0.5% (6 % to 12 %)
... ........ .. ....

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Separation
L into R
or R into L.. ..•...•... . .•. . 55db
Crosstalk
Main into Sub ... .. .. ................. 65db
Sub into Main ....... ... ......... . .... 65db
SCA into Sub or Main .. ... ... . ... . .... 70db
Pilot into Sub or Main •• ........ . .. .. 70db
Monitoring Modes
1) Left
2) Main
3) Pilot Level
4) 38KHz
5) FM/S/N
6) SCA Inj. narrow
7) SCA Inj. wide
Distortion (Left or Right)
Right
Sub
Phase Cai .
Gen. Phase
AM S/N
Main
SCA Mod .
THO .•... . .......... . .. • ........ . .... .0. 05 %
I
MD . .. .• .. .. .. ..... . .. . ..... . ........ 0.1%·( SMPTE)
SCA (4KHz dev.) ........... . .. .. • ..... 1% (50 Hz . to 5KHz) (150us de-emp )
Outputs
Left.•
.. . .. ... .. .• ....•.. .• . .. .. ..... +10 dbm bal . · a~d Hi-z
Right... .
.. . ... .. . .... . .. . ........... +10 db mbal . and Hi-z
Scope ........ . ..............••. • .. .• .1 V8p
Frequency ........... . . •. . . ......... . . X. , I. F. Pilot, SCA (TTL)
Spectrum Analyzer Output .... ........... 70db; +120KHz or +400 K Hz
X (horix. ). ...........•..... • .. • ..... 4V~p
Y (vert.) ........•............. . ... •. 0.5V / 10db
1-3 MECHANICAL SPECIFICATIONS
Dimensions .. . ...... . .. . .•........... . .. lO ½" H X 19
11
WX 12
11
0
Weight ........... .. .. ............. . .... 16 lbs.
Maximum Operating Temp ... . .. • ...... . ... 122°F (5 o0 c) Ambient

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1-4 INSTRUMENT IDENTIFICATION
This unit is identif i ed by a Model and Serial Number located on the rear panel .
All correspondence to your sales representati
ve or the factory in regard to the
unit should reference the comp l ete Model and Serial Numbers.
1-5 OPTIONS
(01) SCA Monitor option (67KHz) consists of the pl ug in board assenbly A6
(02) SCA Monitor option (special frequency) (not FCC Type Approved)
(03) CCIR Specifications (not FCC Type Approved)

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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.
2-2
PREPARATION FOR USE
The unit is designed to be mounted in a standard 19
11
rack. Air space should
be provided above and below the unit so that heat generated by the circuitry
may be dissipated. Additional cooling may be 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 countersink screws and finishing washers.
The unit requires a 105-125V single phase, 50/60Hz power source or a 120-250V
single phase, 50/60Hz pow er source. The identification plate on the back
panel shows for which power source the unit is wired. See Section 5-7 for
inf ormation on changing taps.
2-3 MONITOR · coNNECTIONS
1. Connect the antenna supplied to monitor ANT connector Jll if off air
operation is desired.
2.
Connect a dummy l oad large enough to handle the RF input to DUMMY LO AD
connector J9 .• A½ watt termination is supplied. The input signal sampler
will handle
up to 50 watts with an adequate external dullllTG' load, thus
allowing
direct measurement of exciters and low power transmitters.
DO NOT OPERATE THIS EQUIPMENT WITHOUT AN ADEQUATE DUMMY LOAD INSTALLED.
3. Connect the RF sample to RF IN connector JlO.
4.
TBl-4 and TBl-5 are 600 ohm balanced left audio output.
5.
TBl-6 and TBl-7 are 600 ohm balanced right audio output.
6.
TBl-8 is 600 ohm unbalanced SCA audio (ref. to gnd.)

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2-4 REPACKING FOR SH I PMENT
NOTE: W ARRANTY MAY BE VOID IF UNIT IS NOT RETURNED IN ORIGINAL PACKING.
NOTE: Before returning a u nit for repair or ca l ibration, contact the factory
or your authorized representative for Return Authorization. Attach a tag
showing owner's name and address. Adescription of the service required
should also
be incl uded. Unit must be shipped prepaid and insured for full
va l ue. USE THE ORIGINAL SHIPPING CARTON AND PACKING MATERIAL FOR RE - SHIPMENT.

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SECTION 3
OPERATION
3-1 OPERATOR CONTROLS AND INDICATORS (FRONT PANEL)
1. POWER Switch and led AlSl and AlCRl apply line power to unit.
2. CARRIER FREQUENCY thumbwheel A1S2 sets unit on desired frequency.
3.
L.O. UNLOCK led A1CR2
Led lights if local oscillator is unlocked or reference is lost.
4. RF LEVEL leds A1CR3 (Hi), A1CR4 (LO), AlCRS (OK)
a. AlCRS (OK) will light and AlCR4 (LO) will go out when there
is sufficient RF input to allow a-curate modulation and signal to noise
measurements. This level will normally
be obtained with the antenna
supplied within the
70dBu contour.
b.
A1CR3 (Hi) will light if an excessive RF sample is applied.
Reduce the RF LEVEL pot on rear panel until A1CR3 estinguishes. AlCRS (OK)
will remain lit with Hi RF level since all required monitor functions will
be in specification. However, AM Signal to Noise will not be accurate be-
cause
of saturation of the IF amplifier. In addition, when A1CR3 (Hi) is
lit, the input mixer is being protected by an input clipper.
5. MUTE Switch A1S3
a. With MUTE switch in ON position unit wil1 mute all signals
below RF LEVEL OK threshold.
6.
COMP Jack AlJl provides a 6Vpp wideband composite signal.
7. DE-EMP AUDIO Jack A1J2 provides a 6Vpp@ 400Hz signal with 75usec
de-emphasis. NOTE: This signal is NOT filtered to remove 19KHz.
.
8. TOTAL MODULATION Displays (Yellow)
a. Meter AlMl in conjunction with MOD METER switch A1S4A provides
total modulation (main, sub and SCA) indication with FCC semi-peak ballistics
switchable to POS or NEG.
b. PEAK MOD thumbwheel AlS5 and lamp AlDSl provide a total modula-
tion peak indicator independent of polarity and settable in 1%increments
from Oto 199 %. This flasher will light from 2 to 4 seconds each time a
peak is detected.
c. 100 % PEAKS PER MINUTE Display A10S2 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-
rides the automatic
reset function and OFF extinguishes the display. This
indication
is intended to monitor modulation peaks for Automatic Transmitter
Systems (ATS) as defined by the FCC in the ATS rules.

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d. CAL pushbutton A1S7 provides a total modulation calibrate
signal. The frequency of this signal is 32KHz . See Section 5 for further
information. NOTE: LO UNLOCK led must light when CAL is depressed.
9.
SCOPE Display (Vector and Spectrum Analyzer)
NOTE: To use these features of the 691 requires an oscilloscope
with X
and Y DC Coupled inputs. The bandwidth of the scope need only be a
few hundred kTTohertz but it must be DC Coupled on both X and Yinputs.
a. Connect VERT (A1J3) to Scope Y input. Connect HORIZ (AlJ4)
to
Scope X input. Set both inputs to DC coupled, 0.5 volts/div .
b.
To view Stereo Vector pattern, depress VECTOR button on A1S4B.
Mono modulation will give a vertical line. Any deviation from vertical in-
dicates
that the station mono balance is incorrect.
c. To use SpectrumAnalyzer feature, depress NARROW pushbutton
on A1S4B. Adjust scope horiz. (X) gain to get full width baseline. Adjust
scope
vert (Y) gain to 0.5/div. Display will be centered on frequency de-
termined
by CARRIER FREQUENCY switch and will be approximately +120KHz and
lOdB/div. Depressing WIDE pushbutton will change dispersion to-approximately
+350KHz. NOTE: WIDE position will cause TOTAL MODULATION display to pin
meter
and peak flasher if MUTE is OFF.
10. PILOT PRESENT indicator A1DS3 and 0ADJ AlRl indicate the presence
of the 19KHz pilot tone and provide monitor phase calibration in conjunction
with 0
CAL position of CHANNEL B DISPLAY SELECT. Pilot 0 ADJ AlRl is set
for a null on CHANNEL Bmeter. This adjustment is accurate even with modu-
lation applied.
11.
SCA PRESENT indicator A1DS4 indicates the presence of SCA. The
DEV switch A1S9 may be set to cause CHAN~EL B SCA MOD display to indicate
100 % at either 4KHz or 6KHz deviation.
12.
FREQ Jack AlJS and switch A1S8 provide a convenient output for an
external counter to read station frequency, pilot frequency or SCA frequency.
To read station frequency requires a counter capable of 10.7MHz. First con-
nect the counter·to the XO jack on the rear panel . If the X.O. is not exactly
8.000000MHz, adjust the piston trirrmer on ·the monitor A2 assembly until it
does. See Section 5 for details. Now connect the counter to AlJS and place
A1S8 to IF position. The counter should read 10.7MHz. If it reads lower,
the·
station frequency is higher by the same number of hertz. Conversely, if
it reads higher, the station frequency is lower. NOTE: Be sure of the
accuracy
of the counter. Also, remove modulation from the carrier when
making this measurement. To measure pilot frequency, place A1S8 in PILOT
position. Frequency read on counter will be 10 times the actual pilot.
This allows a counter with only a one second gate time to read to .lHz
accuracy.
To measure SCA frequency, place A1S8 in SCA position. NOTE:
Remove modulation from SCA when making this measurement.

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13. OUTPUT SELECT Switch AlSlO, AUDIO Jack A1J6 and SCOPE Jack A1J7
provice distortion measuring outputs and scope observation output. Switch
AlSlO in LEFT/CHAN A position provides left deemphasized audio with a cutoff
frequency of lSKHz for stereo distortion measurements at AlJ6 and whatever
is displayed on the CHANNEL Ameter at A1J7 for scope observation. When
AlSlO is in RIGHT/CHAN B posit ion, right audio is provided at A1J6 and
Channel B signal appears at AlJ7.
14.
SCA Audio Jack AlJ8 provides 150usec deemphasized SKHz bandwidth
SCA audio for distortion measurements.
1
5~ TEST DISPLAYS (CHANNEL A - green) (CHANNEL B - blue) and DISPLAY
SELECT switch AlS ll
a. DISPLAY SELECT switch controls the signal components to be
displayed.
b. Meters A1M2A and A1M2B in conjunction with+/- switches
A1S13A and A1S13B, MOD; HOLD: AUTO switches A1S14A and A1Sl4B and RANGE
(- dB) readouts A1DS5A and AlDSSB prov i de two metering displays with a
range
of Oto 133 %with FCC ballistics (MOD position) or - 70d8 to +3dB
with semi VU ballistics (AUTO or HOLD position). These displays may be
sw it ched to+ or -indications and may be deemphasized by pushbuttons
A2Sl5A or A1S15B . NOTE: FM and AM S/N are automatically deemphasized.
c.
PEAK thumbwhee1s AlS12A and A1S12B and 1 eds AlCR6A and AlCR6B
provide a peak indication of the corresponding meter display settable in 1%
increments
from Oto 199 %.
3-2
OPERATOR CONTROL AND CONNECTIONS (REAR PANEL)
1. DUMMY LOAD Jack A1J9 - A DUMM~ LOAD ADEQUATE FOR THE RF INPUT
SUPPLIED MUST BE INSTALLED AT THIS JACK . A½ watt load is supplied with
the
unit.
2. RF INPUT Jack AlJlO -Transmitter RF sample connects to this jack.
3.
CARRIER LEVEL Control A1R2 -This control is used to reduce RF
Input below RF HI threshold.
4.
ANT Jack AlJll - 75 ohm FM Antenna connects to this jack.
5.
X.O. OUT Jack A1J12 - 8MHz sample from crystal reference oscil lator
is avai1ab1e at this jack for measurement purposes.
6.
S.A. CENTER Control A1R3 -Control used to center Spectrum Analyzer
display.

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7. COMPOSITE EXT INPUT A1J l3 - Th is input all ows a composite signal
to be a pp lied direct ly to the Stereo and SCA circui ts of the monitor bypas -
sing the
RF demodu l ator.
8. COMPOSITE EXT LEVEL Control Al R4 -Sets external composite signal
l
eve l .
9.
COMPOSITE Switch AlS16 - This switch must be in INT position to
use RF d emodu l ator . In EXT position signal app lied to COMPOSITE EXT INPUT
Al J13 is f ed to stereo and SCA circuits.
3-3 MONAURAL MEASUREMENTS
1. Total Modulation
Set the
CARRIER FREQUENCY thumbwheel to the desired frequency and
MUTE switch to ON. Ver i fy . that L.O. UNLCOK l ed is out and that RF LEVEL
OK led is lit. Al l ow a few seconds for the monitor to stabil ize on the
frequency selected. Adjust the
PEAK M OO thumb wh eel to the desired level.
T
he amber PEAK MOO l amp wil l fl ash for 2 to 4 seconds each time the modu-
l at i on exceeds the preset PEAK MOD level in either a positive or negative
direction.
The TO T AL MODULATION meter responds to total modu lation with
FCC specified ba l listics and may be switched to read either posit i ve or
negative modu lation w it h the MOD METER POS or NEG pushbuttons.
NOTE
The Total Peak Mod Flasher and Total Modulat i on Meter will
only agree if the
transmitter is modulated by a low distor -
tion si ne wave. Any disto r tion wi ll cause posit i ve to nega-
tive assynmetry approximately double the amount of the dis-
tortion in percent. Remember thet the flasher reads the
highest
po l arity and that the meter reads the selected
pol
arity. The difference in readings with program material
is
due to many factors such as the amount of audio dynamic
range compression, transmitter overshoot, program assymmetry,
etc.
The 1 00 % PEAKS PER MINUTE readout counts the number of positive or negative
100 %peaks occuri ng within one minute. This counter was designed to show
compliance with FCC ATS rules. Therefore, it counts 5 millisecond peaks
as ~er FCC rules 73.342(b)3. However, the required PEAK MOD flasher must
rema in lit for 2 to 4 seconds each time it triggers per FCC rules 73.332(D)4i.
This
means that it is possible to get many ATS 5 mill i second peaks during one
flash of the PEAK MOD flasher. Si n ce the ATS rules al low 10 (ten) 100 %5 mi l li-
second peaks per minute; t he readout flashes at 10 and has a maximum count of
19. It automatical ly resets at one minute in tervals and may be manual ly reset
or turned off wi th i ts associated switch.