Kenwood RA-920 User manual

RA-920
RESISTANCEATTENUATOR
INSTRUCTIONMANUAL

YouarenowtheownerofournewproductRA-920.
Thisunithasbeencarefullyengineeredandmanu-
facturedunderourrigidqualitycontrolandshould
giveyousatisfactoryanddependableoperationfor
manyyears.Iftroubleisencounteredortheunitis
damagedintransit,pleasecontactyourdealerorthe
nearestservicestation.
CONTENTS
Features3
Specifications3
CircuitDescription4
ControlPanel5
Cautions7
Applications8
PartsList11
P.C.Board17
SchematicDiagram19

FEATURES SPECIFICATIONS
*Accurateattenuationovera widerangefromDCto
1MHz.
*Metallicfilmresistorsareusedthroughoutthecircuitry
toprovideexcellenttemperaturecharacteristicandac-
curateattenuationaccuracy.
*Adoptionofphasecompensationeliminatesphasedevia-
tioninhighfrequencies,permittingattenuationof
pulsesignals.
*Sincethecaseisofthefloatinggroundsystem,theunit
canbereadilyconnectedtoanelectronicdevicehaving
adifferentcasepotential.Bygroundingthecase,the
measurementaccuracyisfurtherimproved.
*Rotaryswitchesareusedforeasydialsetting.
3
FrequencyRange:DC-1MHz
AttenuationRange:0-121dB(0.1dBstep)
Input/OutputImpedance:600ohm,± 10ohm
MaximumInputLevel:+27dBmor0.5Wor17Vrms
AttenuationAccuracy(lkHz):
Lessthan±0.2dB
Lessthan±0.1dBfor1 dBsteprange
Lessthan±0.01dBfor0.1dBsteprange
FrequencyCharacteristic(referencefreq.1 kHz)
DC-80kHz:±0.2dB(0-121dB)
DC-100kHz:±0.2dB(0-100dB)
DC-150kHz:±0.5dB(0-100dB)
DC-150kHz:±1dB(0-121dB)
DC-1MHz:±1.5dB(0-60dB)
MaximumFloatingVoltage:
(DC+ACpeak):±600V
AmbientTemperature:23°C±10°C
OperatingTemperature:0°C- 50°C
Dimensions:335(W)x 87(D)x 105(H)mm
Weight:2 kg
Accessories:Instructionmanual1
Shortingbar1
Cover(option)Standard
AccessoryforRA-920(A)

CIRCUITDESCRIPTION
1. OutlineofCircuit
Fig. 1 showstheblockdiagramofthecircuit.Thelarge
attenuationrangesuse"T" ordouble"T"networkand
thesmallattenuationrangesuseBridge"T" networks.
Eachstephas600ohmimpedanceandisprovidedwith
capacitorsforphasecompensation.
2. "T",Double"T" andBridge"T"Networks
The"T"networkisusedinthecircuitwheretheat-
tenuationperstepislarge,whilethedouble"T"net-
workisusedwheretheattenuationperstepexceeds40
dBsothattheeffectofstraycapacitanceisminimized
andtheaccuracyisfurtherimproved.
Accordingly,whentheattenuationperstepis60dB,the
errorcausedbya singlestage"T"networkis± 60edB,
butcanbereducedto± 42£dB(seeNOTEbelow)ifit
isdividedintotwostages.
NOTE: ± V(30£)2 + (30e)2=± 42e dB,
wheretheaccuracyofresistorsis± £ (%).
Thebridge"T"networkisusedinthecircuitfromwhich
smallattenuationsareobtained.Thereasonfortheuse
ofthisnetworkistoreducethenumberofresistors.
Input
COM
GND
1
Shortingbar
30dB
"T"
networkx 2
10dB
"T"
networkx 5
1dB
Bridge"T"
networkx 10
Groundplate
Caseground
Fig. 1 BlockDiagram
0.1dB
Bridge"T"
networkx 10
Output
COM
4

CONTROLPANEL
Fig. 2
5

CONTROLPANEL
Reference
No.
Marking Descriptions
1 INPUT Inputterminal:Connecta shieldedcableorcoaxialcablebetweenthesignalsourceandthis
terminal. Thecablelengthshouldnotexceed1 m.
2 Circuitcommonterminal:Connectthisterminaltothecasegroundusingtheshortingbar.
3 Caseground:Thisisconnectedtothecommonterminal2.Itisadvisabletogroundthecasefor
improvedaccuracy.
4 OUTPUT Outputterminal:Theloadimpedanceshouldbe600ohm.Ifthisterminalistobeconnectedto
acircuithavinganimpedanceveryhigherthan600ohm,inserta 600ohmresistorbetweenthe
commonterminal5 andtheterminal4.
5 Commonterminalforoutputside.
6 30dBSTEP Dialfor0-30-60dBattenuation.
7 10dBSTEP Dialfor0-10-20-30-40-50dBattenuation.
8 1 dBSTEP Dialforsettingattenuationsof0 to10dBin1 dBstep.
9 0.1dBSTEP Dialforsettingattenuationsof0 to1.0dBin0.1dBstep.
6

CAUTIONS
1. ThesignalvoltageappliedtoINPUTshouldbelower
than17Vrms.
2. Toavoidleakageofsignalandminimizetheeffectof
phasedeviation,besuretouseshieldedcablesonthe
inputandoutputoftheunit.Thesecablesshouldbeas
shortaspossible.Thisisparticularlyimportantwhen
pulsesignalsareusedasa signalsource.
3.Whentheunitisusedwiththecasegroundfloatedfrom
thecircuitground,thepotentialdifference(DC+ AC
peak)betweenthesetwopointsshouldnotexceed
±600V.
4. Dialsetting
Selectappropriatedialsforthedesiredattenuationat
anyfrequency.Notethatthemarkingsoneachdial
indicateapproximatesettingsofattenuationincluding
error.A typicalexampleofattenuationerrorandfre-
quencycharacteristicerrorisshowninTable1,where
100kHzsignalisattenuatedto100dB,e istheerror
3
at1 kHzofeachdialand£fistheerroroffrequency
characteristic.
Theoverallerrordependsonthenumberofdialstobe
usedasexplainedbelow.
I)Whenthedialsaresetto30dBx2=60dB,10dBx 3
=30dB,1 dBx 9 = 9 dBand0.1dBx 10= 1 dB,
thentheoverallerror(e) causedbyeachdialand
frequencycharacteristicisobtainedfromthefollow-
ingequation:
£= ±V(0.152 + 0.12)+ (0.12+0.12)+ (0.12+0.052;
+ (0.012 +0.052)=±0.28dB
II)Whenthedialsaresetto30dBx 2 = 60dB,10dBx
4= 40dB,then:
£= ±V(0.152 + 0.12)+ (0.12+ 0.12)= 0.23dB
Aswillbeunderstoodfromtheaboveequations,the
lessthenumberofdials,thehighertheaccuracy.
Table1.TypicalExampleofAttenuationErrorand
FrequencyCharacteristicError
Error 30dBstep 10dBstep 1dBstep 0.1dBstep
±0.15dB ±0.1dB ±0.1dB ±0.01dB
£f ±0.1dB ±0.1dB ±0.05dB ±0.05dB
7

APPLICATIONS
1. Measurementofamplifiergain
Example:Audiofrequencies,455kHzIFfrequency,
pulseamplifier,etc.
Connectanoscillator,RA-920,amplifiertobetested
andACvoltmeter(DCvoltmeterforDCamplifier)using
switchessufficientlydurableagainstfrequenciesand
currents,asshowninFig.3.Settheloadimpedanceof
RA-920to600ohm.
1)SetRA-920to0 dB(maybeattenuatedtoa certain
leveldependingontheconditionofoscillator).
2)SettheswitchestotheB positionandreadthe
indicationofthevoltmeter.
3)Next,settheswitchestotheA position.AdjustRA-
920sothatthereadingonthevoltmeteristhesame
asattheB position.Thereadingobtainedisthegain
oftheamplifier.
Whena DCamplifieristobetested,besurethatthe
inputleveldoesnotexceedthemaximuminputvoltage
oftheamplifier.NotethatiftheinputimpedanceofDC
amplifier,etc.islowerthan600ohm,theerrorbecomes
larger.
Amplifier
undertest
Oscillator RA-920 AC
voltmeter
Fig. 3
8

APPLICATIONS
2. Measurementofpulsecircuitthresholdlevel(Fig.4)
1)Adjustthevoltageofpulsecircuittoa properlevel
(5-1OVforTTL),thensetRA-920to0 dB.
2)AdjustRA-920sothattheoutputdisappearsfromthe
oscilloscope!
3)WherethereadingofRA-920is5,thethresholdlevel
iseQ,andthepulsegeneratoroutputisej,
e0= ejXLOG-1
Inmeasurement,besurethatthepulsefrequencyis
below100kHz,thesignalisproperlysheildedand
theloadimpedanceisadequate.
3.Audiomixing(Fig.5)
ByusingtwoRA-920,itispossibletoattenuatetwo
individualsignalsforaudiomixing.
Oscilloscope
TRIG
Speaker
Speaker
Fig. 4
Fig. 5
9
Pulse
generator RA-920
60on
Pulse
circuit
MIC
amplifier RA-920
Tape
recorder RA-920
Mixing
amplifier Main
amplifier

APPLICATIONS
4. Measurementofnoise(Fig.6)
IfthenoiseindecesofA andB areexpressedbyFjand
F3respectively,theamountofattenuationisexpressed
byL2/andthegainGi ofA issufficientlylarge,
Fj•=RtlL2~Ft2La'(F1»-)
L2" - L2'G
FtjandFt2areFt(overallnoisefigure)whereL2isL2'
andL2"
Measurementofnoiseshouldbeperformedaftercheck-
ingthecircuitsystem.
Fig. 6
10
Signalgenerator
or
noisegenerator
Amplifier
undertest Variable
attenuator
Auxiliary
amplifier ACvoltmeter
RA-920

PARTSLISTOFRA-920
SCHEMATICSYMBOL PARTSNO. DESCRIPTION
A01-0813-02
A21-0815-13 Case
Panel
B40-0765-14
B42-1933-04
B50-2828-10
Nameplate
Label
Instructionmanual
C91-0505-05 Oilcapacitor
0.0047,uF
E23-0507-03
E21-0150-03
E21-0151-03
E21-0653-03
E29-0506-04
Groundingplate
Terminal(grey)X 2
Terminal(orange)X 2
Terminal(blue)
Shortingbar
H01-2817-14
H1 2-0514-02
H25-0825-04
Packingcase(individualpacking)
Packingmaterial,foamedstyreneX 2
Polyethylenebag
J02-0503-15 RubberlegX 8
K01-0058-25
K21-0808-03
K21-0809-03
K21-0810-03
K21-0811-03
Grip
Knob,for30dBstepattenuator
Knob,for 1 0 dBstepattenuator
Knob,for1 dBstepattenuator
Knob,for0.1dBstepattenuator
X75-1050-00
X75-1060-00
X75-1070-00
X75-1080-00
30dBstepunit
10 dBstepunit
1dBstepunit
0.1dBstepunit
11

PARTSLIST OF X75-1050-00
SCHEMATICSYMBOL PARTSNO. DESCRIPTION
RESISTOR
R401 R92-0734-05 Metalfilm563.2ft±0.5%1/2W
R402 R92-0733-05 Metalfilm37.9911±0.5%1/2W
R403, 404 R92-0734-05 Metalfilm563.2ft±0.5%1/2W
R405 R92-0733-05 Metalfilm37.99ft±0.5%1/2W
R406 R92-0735-05 Metalfilm
1,126kft±0.5% 1/2W
R407 R92-0733-05 Metalfilm37.99ft±0.5%1/2W
R408 R92-0734-05 Metalfilm563.2ft±0.5%1/2W
CAPACITOR
C402 CM93BD2A132J Mica
1,300pF +10%
MISCELLANEOUS
J25-2819-04 Printedcircuitboard
S401a,b S01-1502-05 Rotaryswitch
PARTSLIST OF X75-1060-00
SCHEMATICSYMBOL PARTSNO. DESCRIPTION
R301
R302 R92-0728-05
R92-0729-05
RESISTOR
Metalfilm311.7ft±0.5%1/2W
Metalfilm421.6ft±0.5%1/2W
12

SCHEMATICSYMBOL PARTS
NO.
DESCRIPTION
R303 R92-0728-05 Metalfilm
311.712
±0.596
1/2W
R304 R92-0730-05 Metalfilm 490.912
±0.5%
1/2W
R305 R92-0727-05 Metalfilm 121.212
±0.5%
1/2W
R306 R92-0730-05 Metalfilm 490.9
a
±0.5%
1/2W
R307 R92-0734-05 Metalfilm 563.2
fl
±0.5% 1/2W
R308 R92-0733-05 Metalfilm 37.9912
±0.5% 1/2W
R309 R92-0734-05 Metalfilm 563.2
fl
±0.5%
1/2W
R310
R92-0730-05 Metalfilm 490.9ft
±0.5%
1/2W
R311
R92-0727-05 Metalfilm 121.212
±0.5%
1/2W
R312
R92-0731-05 Metalfilm 981.812
±0.5%
1/2W
R313
R92-0727-05 Metalfilm 121.212
±0.5%
1/2W
R314,315 R92-0730-05 Metalfilm 490.9*2
±0.5%
1/2W
R316
R92-0727-05 Metalfilm 121.212
±0.5%
1/2W
R317
R92-0732-05 Metalfilm 1.054k fl
±0.5%
1/2W
R318
R92-0733-05 Metalfilm 37.99A
±0.5%
1/2W
R319
R92-0734-05 Metalfilm 563.2
fl
±0.5%
1/2W
CAPACITOR
C305 CM93BD2A471J Mica 470PF
±10%
MISCELLANEOUS
J25-2820-04 Printedcircuitboard
S301a,b
S01-1503-05 Rotaryswitch
13

PARTSLIST OF X75-1070-00
SCHEMATICSYMBOL PARTS
NO.
DESCRIPTION
RESISTOR
R201
RN14BK2H73R2F Metalfilm 732ft
±1% 1/2W
R202 RN14BK2H82R5F Metalfilm 82.5ft
±1%
1/2W
R203 RN14BK2H93R1F Metalfilm
93.1ft
±1%
1/2W
R204 RN14BK2H1020F Metalfilm
10.2ft
±1%
1/2W
R205 RN14BK2H1
150F
Metalfilm 1
15ft
±1% 1/2W
R206 RN14BK2H1300F Metalfilm 130ft
±1%
1/2W
R207 RN14BK2H1470F Metalfilm 147ft
±1% 1/2W
R208 RN14BK2H1650F Metalfilm 165ft
±1%
1/2W
R209 RN14BK2H1820F Metalfilm 182ft
±1%
1/2W
R210
RN14BK2H2050F Metalfilm
205ft
±1% 1/2W
R211
RN14BK2H261 1F Metalfilm 2.61ft
±1% 1/2W
R212
RN14BK2H8660F Metalfilm 866ft
±1%
1/2W
R213
RN14BK2H4320F Metalfilm
432ft
±1%
1/2W
R214
RN14BK2H2550F Metalfilm 255ft
±1%
1/2W
R215
RN14BK2H1690F Metalfilm 169ft
±1%
1/2W
R216
RN14BK2H11 80F
Metalfilm
118ft
±1%
1/2W
R217
RN14BK2H86R6F Metalfilm 86.6ft
±1%
1/2W
R218
RN14BK2H66R5F Metalfilm 66.5ft
±1%
1/2W
R219
RN14BK2H53R6F Metalfilm 53.6ft
±1% 1/2W
R220 R92-0791
-05
Metalfilm 277ft
±0.5%
1/2W
R221,222 R92-0792-05 Metalfilm
600ft ±0.5%
1/2W
CAPACITOR
C201,202 CM93BD2A201J Mica 200PF
±5%
C203 CM93BD2A330J Mica 33PF
±5%
C204 CM93BD2A101
J Mica 100PF
±5%
14

SCHEMATICSYMBOL PARTS
NO.
DESCRIPTION
S201 a, b
J25-2821-04
S01-1 504-04
MISCELLANEOUS
Printedcircuitboard
Rotaryswitch
PARTSLIST OF X75-1080-00
SCHEMATICSYMBOL PARTS
NO.
DESCRIPTION
RESISTOR
R101
RN14BK2H6R98F Metal film
6.98A
± % 1/2W
R102
RN14BK2H14R0F Metal film
14.00 +' 96 1/2W
R103
RN14BK2H21 R5F
Metal film
21.5A ±" % 1/2W
R104
RN14BK2H28R7F Metal film 28.712
±" % 1/2W
R105
RN14BK2H36R5F Metal film 36.52
±-% 1/2W
R106
RN14BK2H44R2F Metal film 44.2A ±1 % 1/2W
R107
RN14BK2H51R1F Metal film
51.1fl ± % 1/2W
R108
RN14BK2H59R0F Metal film
59.0fl ±1 % 1/2W
R109
RN14BK2H68R1F Metal film
68.1fl ±1 % 1/2W
R110
RN14BK2H76R8F Metal film 76.8A
±1 % 1/2W
R1 1 1
RN14BK2H2612F Metal film
26.1kfl ±1 % 1/2W
R112
RN14BK2H8661F Metal film
8.66kfl
±1 % 1/2W
R113
RN14BK2H4321F Metal film
4.32kfl
±' % 1/2W
R114
RN14BK2H261 1F
Metal film 2.61kfl ±1 % 1/2W
R115
RN14BK2H1741F Metal film
1 74kfl
±1 % 1/2W
R116
RN14BK2H1241F Metal film
1.24kfl
±1 % 1/2W
15

SCHEMATICSYMBOL PARTSNO. DESCRIPTION
R117 RN14BK2H9310F Metalfilm 931ft
±1%
1/2W
R118 RN14BK2H7150F Metalfilm 715ft
±1% 1/2W
R119 RN14BK2H5760F Metalfilm 576ft
±1% 1/2W
R120 RN14BK2H511 1F Metalfilm
5.11kft ±196 1/2W
R121.122 RN14BK2H4870F Metalfilm 487ft
±1%
1/2W
MISCELLANEOUS
J25-2822-04 Printedcircuitboard
S101a,b S01-1504-04 Rotaryswitch
16

P.C. BOARD
X75-1060-00
17
X75-1050-00

18
P.C. BOARD
X75-1070-00 X75-1080-00

*Specificationsanddesignaresubjecttochangewithoutnoticeforimprovement.
RA-920
19
SCHEMATICDIAGRAM
PC1J25-2819-04 PC2J25-2820-04 PC3J25-2821-04 PC4J25B-2822-04
OUTPUT
) 60011
INPUT
600I1(

KENWOODCORPORATION
2-5,1-Chome,Shibuya,Shibuya-ku,Tokyo150,Japan
©26410PRINTEDINJAPANB50- 2828- 20(K)