Comtech EF Data EQ90 Series - Manual (Page 31)

EQ90 Amplitude Equalizer Operation
Rev. 2 3-7
The 10-section 70 MHz (140 MHz option) delay equalization PCB is contained in the
internal equalizer assembly A1 and A2. The PCB contains a switch which enables or
disables the alarm output from the equalizer due to a low IF output signal level.
•
Removing the equalizer top cover accesses the BYPASS/LVL MON switch (8,
Figure 3-3).
•
The cover on the internal assembly A1 or A2 is labeled BYPASS or LVL
MON.
•
In the LVL MON position, the IF output signal is monitored. In the event the
IF signal level falls below -20 dBm nominal, an alarm is indicated on the
front panel of the equalizer and reported to external monitor and control
equipment.
•
In the BYPASS position, an alarm will result only if the internal power
supply fails.
The equalizer is made up of 6 or 10 equalizer sections with four adjustments and one
IN/OUT switch (4, Figure 3-3) for each section.
•
The R switches (1, 5) affect the amplitude characteristic of each section in the
equalizer.
•
Adjustment of the L switch (2) 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.
•
The C switch (3) control the center frequency of the delay peak. As the
frequency of the delay peak is varied from 52 to 88 MHz, the magnitude of delay
over a
36 MHz bandwidth centered on the delay peak frequency will remain essentially
constant.
•
The IN/OUT switch (4) inserts or removes the equalizer section from the signal
path.
Each section of a module is initially adjusted separately with all other sections bypassed
by setting the associated IN/OUT switch (4) to out.
The test setup for measurement of the group delay and amplitude response is shown in
Figure Chapter 3-4. The following procedure describes the four adjustments made to one
equalizer section:
•
Equalizer Adjustment
•
Alignment to a Specific Delay Requirement
•
Slope Equalizer Adjustment
•
System Integration Alignment Procedure