Setting up the FM amplifier box
After installing, switching on and calling up the box with the
+
or
–
button on the control unit of the Headend station, the box responds with the
indication in the diplay as shown in the Fig. to the left, for example.
In order to prevent intermodulation, the possibly too high signal levels of local
stations can be cut by up to 6 tuneable traps.
If necessary, it is also possible to tune 2 traps to the same frequency to obtain a
higher signal attenuation.
We recommend you to use a spectrum analyzer to carry out the following
settings.
Follow these steps:
1
Connect the RF input of the spectrum analyzer to the RF output of the Headend
station then select the FM range on the spectrum analyzer.
2
Turn the control for the input level and the control for the output level of the
box clockwise to its right end stop (= maximum level).
Important:
Only the controls of the first group of 3 controls (traps 1–3) can be
combined with any desired control of the second group of 3 controls
(traps 4 –6). Within the same group the traps influence each other when
tuned to the same frequency and can therefore not be used for an appro-
priate signal attenuation.
3
Use the level controls of the traps »
1
–
3
« and »
4
–
6
« to adjust the input level
of the „strong” FM stations (local stations) to the level of the “normal” FM
stations.
– With that it is achieved that all receivable FM stations are fed with nearly
the same signal level into the house distribution system.
Note:
To prevent interferences inside the Headend station and the cable system, it is
necessary to cut the output level of the FM stations by about 10 dB with
respect to the analog TV channels.
Example:
Output level of the TV channels about 100 dBµV,
output level of the FM stations about 90 dBµV.
4
Use the control for the input level of the FM amplifier box to cut the output
signal level by about 10 dB (= 90 dBµV).
– If this value cannot be obtained, the output signal level can also be cut (by
max. - 20 dB) using the control for the output level of the amplifier box.
SETUP
_____________________________________________________________________________________
Box 4
FM:
87 – 108 MHz
UKW
6
