Comtech EF Data EQ90 Series - Manual (Page 34)

Operation EQ90 Amplitude Equalizer
3-10 Rev. 2
Adjustment of the variable inductors, L switch (2, Figure 3-3) will affect the frequency
of peak delay as well as the magnitude of the delay peak. The variable capacitors are
used to return the delay peak to its initial center frequency (Figure Chapter 3-6).
When the capacitors and inductors are varied, the flatness of the amplitude
characteristics changes. The effect of varying the R switch (1, Figure Chapter 3-3) upon
amplitude response is shown in Figure Chapter 3-7. This adjustment affects the
amplitude tilt rather than peaking. An amplitude slope appears near the frequency of the
delay peak.
The effect of varying the R switch (5, Figure Chapter 3-3) upon amplitude is shown in
Figure Chapter 3-8. This control adjusts the degree of peaking or amplitude depth near
the vicinity of the delay peak.
The variable capacitors can vary the delay peak frequency beyond the 52 to 88 MHz
(104 to 176 MHz) frequencies for all values of inductance. The inductance can vary the
peak delay over 36 MHz bandwidth from <15 to> 40 ns peak-to-peak. The amplitude
adjustments can always return the amplitude response for the equalizer to
≤
0.15 dB
peak-to- peak.
After changing the frequency of peak delay for any section, the amplitude may require
readjustment for maximum flatness before proceeding to adjust another section. When
properly adjusted for amplitude flatness, bypassing the equalizer section will generally
effect the overall gain by
≤
0.3 dB.
When two or more adjacent sections are inserted into the signal path there will be an
interaction between sections. This interaction is reflected only in the overall amplitude
response characteristic and is at its worst when all sections are tuned to the same
frequency. Thus, the frequencies between sections are staggered as much as possible to
minimize the interaction.
Complete the module adjustment by adjusting the GAIN ADJ potentiometer
(6, Figure Chapter 3-3) control to provide an overall gain of 15 dB and SLP ADJ
potentiometer (7) control to minimize overall amplitude slope. Record the delay shapes,
frequencies, and amplitude responses of each section separately to provide a future
reference point in the event a module fails and must be replaced.