Tektronix 494AP service manual PerformanceCheck procedure- 4g4A/4g4ApServiceVol, Freorange

PerformanceCheck procedure- 4g4A/4g4ApServiceVol. 1

Spactum Analtrar Un(br Totl

alC T{oilt clot

Figure 4'16.Test equlpment setup for checking intermoduration distortion.

o o

t

o

a

o

O

a o

Io

I

o a o

I

I

a o

freq . - .. t,	f1	t2
Third (3rd) Order Intermodulationproducts			2127_.ts

b. Set the generatoroutputs approximately2 MHz apart withinthe frequencyrange of band 1, and set the outputlevelsfor fullscreensignals.

c. Decreasethe separationof the generatorfre- quenciesto 1 MHz. Reset the spAN/Dlv to 500kHz AndRESOLUTIONBANDWIDTHto 1OKHz.

d. Check that the third order lM productsare at least 70 dB down trom the input signallevel. See Fig- ure4-17.

t

o o o o o o o o

Figure4-17. Intermodulatlonproducts.

22. Check IntermodutationDistortion fl-hirdorder productsat least70 dB down from anv two on-screensignals)

a.connectthe test equipmentas shownin Figure 4-16,and set the SpectrumAnalyzercontrolsas fol- lows:

FREORANGE	0 - 1 . 8 (Band1)
CENTERFREQUENCY	Within 2 MHz of
sPAN/DrV	Test Generators
	5 M H z
RESOLUTIONBANDWIDTH 100 kHz
REFLEVEL	- 30 dBm
MINRFATTENdB	n
VERTICALDISPLAY	10 dBiDrv
TrME/DrV	AUTO

4-28

Use the VideoFilterand very slow sweep ratesto helpresolvethesesidebands.

e.Decr€asethe signal separationand SPAN/DIV settingsand re-checkfor sidebands.Checkfor lM pro-

ducts at olher spans of the frequencyrange. lM pro- ducts shouldbe -70dBc or more.

f.Changethe FREQUENCYRANGEto Band 2 (1.7-5.5 GHz),FREQSPAN/DIVto 5 MHz,andRESO- LUTIONBANDWIDTHto 100kHz.

g.Reset the generator outputs approximately 2 MHz apartwithin the frequencyrangeof band2, and set the outputlevelsfor full screensignals.Reducethe SPAN/DIVand RESOLUTIONBANDWIDTHso the noise floor is at least70 dB downfrom the referencelevel.

h.Checkthat lM productsare at least70 dB down from the inputsignallevelor top of the screen.

o o

to

o o

t

I

C

a a

O

o o o o