HP 8568B Note, Adjustments, Bandpass Filter, Second Converter

19. Second Converter Adjustments

Second ConverterBandpass FilterAdjustments

Note

27.Key in m (JJ) T, [FREQUENCY SPAN] 0 Hz.

28.On the synthesized sweeper, key in ICF) 240 MHz, a 50 MHz,

and CPowerLeVel] - 10 dBm.

29.Connect the synthesized sweeper’s SWEEP OUTPUT (rear panel), Z-AXIS BLANK/MKRS (rear panel), and PULSE MODULATION INPUT (front panel) to the proper rear-panel connectors on the scalar network analyzer as shown in Figure 3-73.

30.On the scalar network analyzer, press PRESET, turn channel 2 off, and press [MEAS] (A/R).

31.Connect the synthesized sweeper’s output to the power splitter as shown in Figure 3-72.

32.Connect one arm of power splitter to scalar network analyzer R input. Connect other arm of power splitter to A input, using a BNC to SMB snap-on test cable and necessary adapters.

33.Set the scalar network analyzer c-1 to 1 dB, and set m (REF LEVEL) to -16.00 dB. Set REF POSN (press REF POSN) to the fourth division from the bottom using the data knob.

34.On the synthesized sweeper, press [m) (ON), [MKR SWEEP), and @FJ. Set @WEEP TIME] to 500 ms.

35.Adjust REF LEVEL for a mid-screen response of the bandpass signal on the scalar network analyzer.

36.Connect the test cable from the power splitter output arm to A23A3J2 Pilot First IF IN.

37.Connect cable 80 (gray/black) from A23A3J6 (PILOT 2ND IF) to the scalar network analyzer’s A input. Set Cm] to 10 dB/DIV.

38.On the spectrum analyzer, key in [SHIFT] (FREERUN)V.

Hold (SHIFT] in until the LED lights, then press I-) until the sweep is free running.

39.On the synthesized sweeper, set (CF) for a frequency of 2017.6 MHz and InF] to 50 MHz.

40.Adjust a on the synthesized sweeper to center the bandpass signal.

41.Adjust A23A3 25, Z6, 27, and L4 for best bandpass shape and flatness at maximum amplitude of signal displayed on Scalar network analyzer. A typical properly-adjusted bandpass filter response is shown in Figure 3-74. See Figure 3-73 for location of adjustments. The bandpass filter response at the 3 dB points should be 222 MHz. See Figure 3-74 and Figure 3-75 for a typical PILOT 2ND IF bandpass response for a SHIFT LO 1 and a SHIFT LO 1.

3-126 Adjustments