Tektronix 494AP service manual O a a o o o o a o A o o o o o, A o a, DB/Dtv

PerformanceCheck procedure- 4g4Al4g4ApServiceVol. 1

19.Check Gain Variation Between Resolution Bandwidths

(Lessthan *0.4 dB with respectto the 3 MHz fitter and lessthan0.8 dB betweenanytwo filters)

Before performingthis check,do a front panelCAL procedureby pressing <Blue-SHIFT> CAL and per_ forming the steps promptedby the spectrumanalyzer.

a.Applythe CAL OUTsignatto the RF tNpUT,and set th€ SpectrumAnalyzercontrolsas follows:

CENTERFREQUENCY	100MHz
SPAN/DIV	100kHz

RESOLUTION
BANDWTDTH 3 MHz
REFLEVEL	-18 dBm
MlN RF ATTENdB	0
VERTICALDISPLAY	1 dB/Dtv
MINNOISE	On
TrME/DV	AUTO

b.Activatethe AA modeby pressingFINE.

c.Resetthe REFERENCELEVELcontrotto position the calibratorsignal at the 7th graticuleline (1 major divisionfrom the top), then activateSAVEA to store the

3MHz amplitude.

d.Change the RESOLUTTONBANDWTDTHto

1MHz.

e.check that amplitudedeviationfrom the 3 MHz referenc€is no morethan *0.4 dB.

f.Change the RESOLUTTONBANDWTDTHto

100kHz andthe FREQSpAN/Dtvto .t0 kHz.

g.Checkthat amplitudedeviationfrom the 3 MHz referencelevelis no morethan f 0.4 dB.

h.R€p9at the procedureto check the remaining filters(10kHz, 1 kHz, 100H2,and 10 Hz)to verifythat the signal amplitude does not change more than +0.4 dB from the 3 MHz referencelevel.

i.Check variation between any two filters (0.g dB) by findingthe filter that has the lowest amplitude,sav_ ing it on the A-trace,then comparingthe otherfiltersto the savedtrace.

20.Gheck Sensitivity (Referto Table4-8)

FREQ RANGE	0-1.8 GHz
sPAN/DrV	MAX
RESOLUTIONBANDWIDTH 10 kHz
REFLEVEL	-100 dBm
MIN RF ATTENdB	0
VERTICALDISPLAY	2 dBlDlV
NARROWVIDEOFILTER	On
V I E W A & V I E W B	On
PEAK/AVERAGE	FullyClockwise
TrME/DrV	1 s

b.Enable a marker by pressingTUNE CFIMKR. Tunethe markerto the highestpointon the noisefloor. Activate zERo SPAN, and change the RESoLUTIoN BANDWIDTHto 3 MHz and the REFERENCELEVELas ncessaryto viewthe baseline.

c.Checkthat the noisefloor (level)is down as per Table 4-8 (at least -80dBm down if checkinga stan- dard instrument,or -31dBmV if checkingthe 7SO inputin an Option07 instrument).

The REF LEVEL will have to be reset each tiME thE RESOLUTION BANDWIDTH iS changed.

d. RESETthE RESOLUTIONBANDWIDTHtO 1 MHZ.

e, Check that the noise floor (level) is down as per TablE 4-8.

f.Reset the RESOLUTION BANDWTDTH to 100 kHz.

g.Check that the noise floor (level) is down as per Table 4-8.

h. RESETthE RESOLUTIONBANDWIDTHtO 1OKHZ.

i.Check that the noise floor (level) is down as per Table 4-8.

j. Reset the RESoLUTIONBANDWTDTHto 1 kHz.

k.Check that the noise floor (level) is down as per Table 4-8.

I. RESETthE RESOLUTIONBANDWIDTHtO 1OOHZ.

m.Gheck that the noise floor (level) is down as per Table 4-8.

N.RESETthE RESOLUTION BANOWIDTH tO 1OHZ. and VERTICAL DISPLAY to 5 dB/DlV.

o o o a a o o o o a o

Io

I

I

t

I

Ia

o a

O

o o a o o o o o

Io

o

o

O

a.conn€ct the cAL ouT signatto the RF tNpuT, and performth€ <Blue-SHIFT>CAL routine. Remove the CAL OUT signalfrom the RF lNpUT, and terminate the FF INPUTin its characteristicimpedance.Set the SpectrumAnalyzercontrolsas follows:

o.Check that the noise floor {level) is down as per Table 4-8.

p.Repeat this procedure for the remaining coaxial input frequency range (1.7 to 21 GHz). lf desired, the sensitivity for the waveguide bands can be checked as per the listings in Table 4-8. The values for the 50 GHz to 140 GHz range are typical and not intended as a per- formance requirement.

I

a a a o a

4-26

o o

o