12
Preinstallation Procedures
MB-750D-H and MB-750D-H/40 Installation Manual
this equalizer installed, the amplifier will reproduce the output tilt of the last upstream
amplifier.
Example 2:
The MB-750D-H* amplifier is to be used in a link following a fiber node. The fiber receiver’s
output is flat and connects to the input of the amplifier through 18 dB of cable plus passive loss.
Which is the proper equalizer to achieve the 10 dB output tilt from the amplifier?
In this instance, the equalizer value can be calculated by using the following method:
SLOPE
eq
= TILT
out
+ SIG
lo
−
SIG
hi
−
SLOPE
ieq
where:
SLOPE
eq
= required EQ-750-* slope
TILT
out
= required amplifier output tilt
SIG
lo
= signal input level at channel 2
SIG
hi
= signal input level at 750 MHz
SLOPE
ieq
= interstage equalizer slope (10 dB)
From established references and manufacturer’s catalogs, note that at an operating frequency of
750 MHz, 18 dB of cable will produce approximately 4.4 dB of loss at 54 MHz. This suggests
that the channel 2 signal input to the MB-750D-H* amplifier is 13.6 dB greater (18
−
4.4 = 13.6)
at channel 2 than at 750 MHz. Our example assumes that the high-end frequency level into the
amplifier is + 12 dBmV.
Substituting this information into the above equation gives:
10 dB + 25.6 dB
−
12 dBmV
−
10 dB = 13.6 dB
The slope of the required equalizer is 13.6 dB. This can be translated into an equivalent cable
value by using either Figure 6 or alternatively, by using the appropriate multiplier. The
multiplier in this case is 1.37 dB (13.6 × 1.37 = 18.6). Therefore, the correct equalizer is the
EQ-750-18, the closest available equalizer value.
Multipliers to convert tilt to cable equivalent are:
550 MHz = 1.46
650 MHz = 1.40
750 MHz = 1.37
The final choice of equalizer could vary somewhat when the amplifier is installed. This is due to
a number of independent variables including errors in cable attenuation, slope in passive
devices, and others.
In cases where the calculated equalizer value makes two choices possible, the lower value is to be
preferred.
Figure 6, on the following page, graphically represents the relationship between dB of cable and
dB of tilt.
