PerformanceCheckprocedure- 494A/4g4ApServiceVol. 1

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d. Check that the signal steps down in 10 dB (r1.0 dB) steps as attenuationis added. Maximum cumulativeerror should not exceed 2.0 dB over the 80 dB range.

e.Deactivatethe NARROWVTDEOFLTER,return the externalattenuationto 0 dB, and changethe VERTI- CAL OISPLAYto 2 dB/DlV. Set the signatpeakat the reference(top)graticuleline, with the generatoroutput control.

f.Add 16 dB of externalattenuationin 2 dB steps, and notethat the displaystepsdown in 2 dB steps.

g, Check the display accuracy as attenuationis added. Error shouldnot exceed+6.+ aep dB step,or exce€da cumulativeerror of +1.0 dB over the i6 dB window.

h.Returnthe externalattenuationto 0 dB. change the VERTTCALDlSpLAy to LtN. Set the signalgenera- tor outputfor a full screendisplay.

i.Check that the signal amplitude decreasesro within *0.4 divisionsof half screenas 6 dB of external attenuationis added.

j.Check that the signal amplitudedecreasesro within i0.4 divisionsot 114screenor hatfthe previous amplitudeas an additional6dB of att€nuationis added.

k.Check that the signal amplitudedecreasesto within *0.4 divisionsot 1lg screen or half the last amplitudeas an additional6 dB of attenuationis added (fora total of 18 dB).

t.Returnths vERTtcALDtspLAy to 1o dB/Dtvand disconnectths generatorfrom the RF lNpUT.

16.Check Preseleclor Ultimate Rejection

This is a check of preselectoropeiation,not a per_ formancerequirementspecification.

a.Connectthe test equipmentas shown in Figure 4-13, omittingthe step attenuators. Set the Spect-rumAnalyzercontrolsas follows:

CENTERFREOUENCY 3.SGHz(Band2)

SPAN/DV10kHz

AUTORESOLN On

REFLEVEL0 dBm VERTCALDTSPLAY 10 dB/Dtv

MINRFATTENdB O WIDEVIDEOFTLTER On

TMEIDIVAUTO

b.Set the generatorcontrols for a full screen displayoutputat 3.SGHz. peak the responsewiththe MANUALPEAKcontrotor pEAKMENUmode.

_ c. Changethe FREQRANGEto band 3 (3.0_7.1 GHz).

d. Checkthat spurioussignalsare at least too dB down from the levelestablishedin part b. Spurioussig- nals above100dB downfrom the referenceestabtished in part b indicatethat the ylG-tunedpreselectorfilter couldbe defective.

17. Check RF Attenuator Accuracy

(Within0.5 dB/10dB to a maximumof 1 dB overthe 60 dB rangefrom dc to 1.8 GHz; within1.5 dB/tO dB to a maximumof 3 dB over the 60 dB range from 1.8GHzto 18 GHz;andwithing dB/10dB to a maximumof 6 dB over the 60 dB range from 1g GHzto 21 GHz)

This is a three part procedure. part I checksthe first 30 dB (0-30 dB) rangeof the rf attenuator,Part ll checksthe remain- ing 30 dB (30dB-60 dB) range for fre- quenciesup to 18 GHz,and part lll checks the 50 dB to 60 dB step of the RF Attenua- tor lor frequenciesabove18 GHz.

PART I

a.Connectthe test equipm€ntas shown in Figure

4-14. Setthe SpectrumAnalyzercontrolsas follows:

CENTERFREOUENCY

Test Freguency

SPAN/DIV

200 kHz

RESOLUNONBANDWIDTH

100kHz

REF LEVEL

-30 dBm

MIN RF ATTEN dB

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M I N N O I S E

On

VERTfCALDISPLAY

2 dBlDtV

NARROWVIDEOFILTER

On

TME/DV

AUTO

PEAK/AVERAGE

FullyClockwise

VIEWA and VIEWB

On

b. Set the power meter controls as follows:

ModeWatts

RangeHold Out

Power Reference Out

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Tektronix 494AP service manual O o a o o o A o, Tmeidivauto, Part, Narrowvideofilter TME/DV Auto PEAK/AVERAGE