IF-Display Section
3 MHz Bandwidth Filter
Resolution Bandwidth Switching Uncertainty Test
Resolution Bandwidth Selectivity Test
With the CAL OUTPUT signal connected to the RF INPUT, the 18.4
MHz oscillator is adjusted with the FREQ ZERO control (on the front
panel) to peak the IF signal for maximum amplitude for the center of
the 3 MHz bandpass. Each of the five stages of the 3 MHz Bandwidth
Filter is adjusted for
centering and symmetry. Four crystal
filter bypass networks are required for alignment of the filter stages.
See Figure 3-109 or information concerning the bypass networks.
A stable 21.4 MHz signal is then applied to the IF section of the
instrument from a frequency synthesizer. Each of the first four stages
of the 3 MHz Bandwidth Filter is peaked in a 10 Hz bandwidth using
an oscilloscope display. The final stage is peaked using the spectrum
analyzer CRT display.
After all five filter stages are adjusted for centering, symmetry, and
peaking, the CAL OUTPUT signal is used to match the 10 Hz and 1
bandwidth amplitudes.
Figure 3-37. 3 MHz Bandwidth Filter Adjustments Setup
3-76 Adjustments
