Tektronix 494AP service manual SPAN/DrV, TlmeMarkGenerator, MarkerOutput, 50 Hz 20 ms

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PerformanceCheckprocedure- 4g4AJ4g4ApServlceVol. 1

i. Reset the REF LEVEL for tho best marker definirion,and the CENTERFREouENcy t" ariln ii.,e ryt9rs so span/divaccuracycan be checkedilr the 50 MHz/div.

j. Reset CENTERFREOUENCYto 100MHz and SPAN/DVto 20 MHz, and apply 50 ns (20frlHzymaif<- ers.

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Figure4S. Typicalmarkerdlsplayfor measuringSpan/Div accutacy.

c. Removethe CALOUTsignatfromthe RF tNpUT and set up the test equipment;s shownin Figure4_7. set the CENTERFREOUENCyto 10 eni, bnlr.rTDtvto 500MHz, RESOLUTTONBANDWIDTHto'100kHz,and REF LEVELto -10dBm. peak the responsewith the MANUALpEAKcontrotand set REFLE'ELfor the best markerdefinition.lt mayalso helpto resetthe CENTER FREQUENCYfor b€ttermarkerdefinition.

d.Tune a markerto center screenthen checkthe accuracyover the centereight divisionsof the display, Deviationmustnot exceed*25 MHz/Div.

E. SEt thE CENTER FREOUENCYtO 2.0 GHZ, SPAN/DIVto 100kHz, RESOLUION BANDWTDTHto 1 If., TME/DV to 50 ms, and REF LEVEL to -20dBm.

f.Modulatethe Comb Generatorsignalwith 1Ops markers,from the Time Mark Generato-r,by applying the MarkerOutputto the pulseInputof tte iomU denl erator.asshownin Figure4-7. S;t the MANUALpEAK controltor optirnummarkerdefinition.

g. . C[e9k SPAN/DV accuracy. Error must not exceed*5 kHz/Div.

h.Removethe CombGeneratorsignalfrom the RF INPUTand connectthe markeroutput6t the TimeMark Generatorto the RF tNpUT. Sei tne CENTERFRE- OIENCYto 2s0MHz,SpAN/DVto 50 MHz,RESOLU- NON BANDWIDTHto 1ookHz, REFLEVELto 20 dBm, and apply20 ns time markersfrom the TimeMark Gen_ erator.

k. check the 20 MHz spAN/DlVaccuracy.

l. Repeatthe procedureand check th€ SPAN/DV accuracyfrom 10 MHz downto 200kHz. UsefaOteq-S as a guideto relatetime markersto spAN/Dlv settings. ReduceRESOLUTIONBANDWIDTHand CENTERFR]E. OUENCYas each settingis checkedto maintainmarker amplitudeand definition.

_ - rn. Change th€ TME/DVto 0.5 s and RESOLU_ TION BANDWTDTHto 1kHz. Repeatthe above pro_ cedure to check the 100kHz to 10kHz SpANfDtV selections.

N. SEt thE CENTER FREQUENCYtO 'IOO KHZ,

RESOLUTTONBANDWTDTHto 100Hz,TME/DIVto.t s and REF LEVELto 0 dBm. Repeat the above pro- cedure to check the S kHz to 20 Hz SpAN/DVselec_ tions,

Tabte4-3

SPAN/DrVVERSUSTMEMARKERSFOR

SPANiDVACCURACYCHECK

CENTERFREQUENCY	TlmeMarkGenerator
sPAN/DrV	MarkerOutput
20 MHz	50 ns
10MHz	. 1 us
5 MHz	.2 us
2 MHz	.5 us
1 MHz	1 u s
500 kHz	2 u s
200kHz	5 u s
100kHz	10us
50 kHz	20 us
20 kHz	50 us
10 kHz	. 1 ms
5 kHz	.2 ms
2kHz	.5 ms
1 kHz	1 m s
500Hz	2 m s
200Hz	5 m s
100Hz	1 0m s
50 Hz	20 ms
Hz

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