Tektronix 494AP service manual A a a o a o, Centebfreouency, Display, Widevideofilter

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PerformanceCheck procedura- 4g4Al4g4ApServlceVol. 1

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.. q: 19.gt the SpectrumAnalyzerRF attenuatorset- ting to 60 dB, and increasethe referencelevel setting by t0 dB.

.r, lheck that t,€ {itEreqce between the SAVEA and.VIEWg.gi.prqfr is \ss t\"n s.ri o-e. Make a note

of th€ levetdiffere(rceOetNqer/ttre n'anOVEWB SnVe

displays. \

s.Usingthe data noted in step o of part l, steps n and o of part ll, and step r of part ttt, ctreckthat devia-

tlon overthe entire60 dB rangeis lessit Og.

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18. Check lF Gain Accuracy

(+0.2.dB/dBStepto a miximumof *0.S dB/g dB
exceptat the decadetransitions				_19	Oemto _eO
dBm,-29		of
	dBmto	__30
		dBm,_3s oam to _40 dBm,
-49 dBm ro -S0		dBm, and _59	dBm io			_60	oBm
wherean additional
		O.SdB canoccurfoi a totatof t

dB/decade.Maximumdeviationoverthe full g7 dB rangeis within+2 dB)

.. T.hf".checkrequirescalibratedattenuatorsto check the 10dB and 1 dB steps. When mafing measure- mentswithin10dB of the noisefloor,a correctionfac- tor shouldbe used to correct for the logarithmicaddi- tionof noisein the system,as shownin fi6te +-2.

	a. Connectth€ test equipment
4-13,usingthe calibrated'1d				as shownin Figure
			dB ano t ae attenuators
!"j ::g^::l			the output-ofthe g"n"r"to, oirecily to the
RF TNPUTif individuat					be used
as			fixed atGnu"tor"
	lhe	standard).Set th€ Spectrum			"r"1o
				Analyzercontrols
as follows:
		CENTEBFREOUENCY		100MHz
		SPANIDtV
				10kHz
		RESOLUTION
			BANDWIDTH 10kHz
		REFLEVEL		- 10 dBm
		MINRFATTENdB		0
		VERTICAL		1 dB/Dlv
			DISPLAY
		WIDEVIDEOFILTER		On
		TrME/DtV		AUTO

SAVEAoff

-b. Setthe generatorcontrolsfor a 100MHz output frequency,anda signalamplitudeot six Oivisions.

c.ActivateMIN NOISEand notesignallevelshift. Levelshift must not exceed *0.g dB, o-,+ minor Oiui_ sions(attenuatorplusgainaccuracies).

d. Set the output of the signal generator	to re-
position
the signallevelat the6th graticuleline.

e.switch ihe REF LEVELfrom _10dBm to _20 dBm in I dB steps,adding.l dB of externatatt€nuation at each step. Noteincrementalaccuracyand the 10 dB

91n.jr9g!racy. Incrementataccuracy must be within 0.2 dB/dB. Maximumcumulativeerroi rnustnot exceed 0.5 dB except when steppingfrorn the g dB to 10 dB increment, where the error could be an addational 0.5 dB. This exception_doesnot apply when stepping from -69dBm to _70 dBm,_79 dBm to _go oem, itc.-

f. DeactivateMtN NolsE. Return the 1 dB step attenuatorto 0 dB, decreasethe output of the sign;l generatorby 10 dB or add l0 dB of externalattenua- tion. Reset the generatoroutput so the signaltevetis againat the 6th graticuleline.

-9.change the REF LEVEL from _20 dBm to

-30 dBm, in 1 dB increments,with the 1 dB stef attenuator,and note incrementaland 10 dB step accu- racies.

h.Return the 1 dB step attenuator to 0 clB. Decrease the signal level by 10 dB with external attenuation,or with the signat generatoroutput fevel control, then re-estabtishthe signal referenceampli_ tude.

i.Checkthe -30dBm to -40dBm gain accuracies as in parte.

j. Repeat the procedurecheckinggain accuracies to -60dBm.

k. Establish a signal reference amplitude of -60dBm, activate NARROW VTOEOFILTER, then checkgainaccuracyto -70dBm.

I.Decreasethe RESOLUTIONBANDWIDTHand SPAN/DIVto 1 kHz. Re-establisha signal reference levelof -70dBm as describedpreviously.

m.Check the -70dBm to -90dBm gain accura- cies by repeatingthe processpreviouslydeicribed.

n.Decrease the RESOLUTTONBANDWTDTH

100Hz and SpAN/DIVto 50 Hz, reestabtishthe signal referencelevel and check the -g0dBm to _gOdBm and -90dBmto -100dBm gain accuracies.These rangesare directlyrelatedto the -60dBm to _70 dBm check(partsd throughm).

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Table 4-7

		CORRECTION
dB Ratio				FACTORTO DETERMINETRUE STGNALLEVEL
of Signal
Plus Noise	3.0	4.0	5.0	6.0	7.0	8.0	9.0	10 . 0	't2.0	1 4 . 0
Correction
Factor	3.0	2.20	1 . 6 5	1 . 26	0.97	0.75	0.s8	0.46	4.28	0 . 18
										4-25

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