Tektronix 494AP service manual O a, CheckLO Emission -70 dBmor tess, Autoresoln, Otsplay

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23. Check Harmonic Distortion

{-60 dBc or tessfrorn10 kHzto 1.gGHz)

{Not discernibleabove ttno]r" ftoor (at teast100dBc)from1.7GHz" "u"r"g"

to 21-cHti

Testedat -90dBm in MIN DTSTORTTON
	mode
a. Gonnectthe test equipment
	as shownin Figure
4-18, and set the Spectrum-
lows:	Analyzer
	"onirolu as fol_
CENTERFREOUENCY Same as Genera-
sPAN/DtV	tor
	5 MHz
AUTORESOLN
	On
REFLEVEL	-30 dBm
MINRFATTENdB	0
VERTICAL	10dB/Dlv
OTSPLAY
WIDEVIDEOFILTER	On
MINDISTORTION	On
VIEWA and VEWB	On
TrME/DtV	AUTO

.b. Note the SpectrumAnalyzerdisplayas the gen- erator frequencycontroris variid auoui ilie centerfre- quencyofthe bandpassfilterif a bandpassfilteris used in the test, or as the frequencyis varied below the cutofffrequencyif a low passfilteris used.

Set the generatorfrequencyat that frequency that yieldedthe maximumamplitudein part b, then set the outputtevetfor a fuil screen(_30Oelnyiign"t.

In Figure4-18,the filtershownmusthavea minimumof 40 dB rolloffto attenuatemulti_ ples of the generatorfrequency,and the frequencyot the signal generatordepends on the frequencycharacteristicsof the fitter.

d.SEt thE CENTER FREQUENCY tO

!2jlLq$lequency), FREQSPAN/DVto 500kHz,and RESOLUTTONBANDWTDTHto 10 kHz.

e.Checkthat the secondharmonicof the inputsig_ nal is at least60 dB belowthe -90 dBm carrier.

f.SEt thE CENTERFREQUENCYtO thE 3rd hAr. monic.

g, Checkthat the third harmonicof the inputsignal is at least60 dB downfrom the -30 dBm carrier.

24.CheckLO Emission (-70 dBmor tess)

a. Monitor the RF INPUT with a hioh frequency spectrum analyzer such as a 4g2A. Set tie test spec- trum analyzercontrols as follows.

PerformanceCheckprocedure- 4g4Al4g4ApServiceVd. l

CenterFrequency 2O72MHz

Span/Div2MHz

MinRF AttendB 0

VerticatDisplay t0dB/DtV

Time/DivAuto

Triggering FreeRun

BaselineClip Otr

ReferenceLevel -70 dBm

Auto Resolution On

ViewA and ViewB On

MdeoFilter Wide

Peak/Average FullyClockwise .

b. Set the SpectrumAnalyzerundertest as foltows:

CENTERFREQUENCY 0Hz

REFLEVEL	-30 dBm
SPAN/DIV	100kHz
MIN RF ATTENdB	0
PEAK/AVERAGE	FullyClockwise

c.Checkfor any indicationof LO emission.LO ernissionmustbe fessthan-70 dBm.

25.Check1 dB Compressionpoint

(-20 dBmBandsI through5)

Calibrate the power meter befora making this measurement.

a.Use the power meterto set the outputlevelof a signalgeneratorto 0 dBm at 1.7GHz.

b.Connectthe test equipmentas shown in Figure 4-19, using th€ generatorwith the calibratedoutput level. Set the SpectrumAnalyzercontrolsas followsi

CENTERFREOUENCY 1 . 7GHz

sPAN/D1V	100kHz
AUTORESOLN	On
REFLEVEL	-30 dBm
MINRF ATTENdB	0
VERTICALDISPLAY	10dB/Dtv
VIEWA andVIEWB	On
TIME/DrV	AUTO

c. Set the attenuatorsfor 25 dB of attenuation.

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