DIAGNOSTICS GUIDE
The RHBDA provides long term, care-free operation and requires no periodic
maintenance. There are no user-serviceable components inside the RHBDA.
This section covers possible problems that may be related to the installation or
operating environment.
a. Gain Reduction
Possible causes: Bad RF cables and RF connections to antennas, damaged
antennae.
b. Excessive Intermodulation or Spurious
Possible causes:
Amplifier oscillation caused by insufficient isolation. The isolation between two
antennae is given by the equation:
Isolation = 92.5 + 20 Log (F x D) – Gt – Gr
Where:
F = frequency (GHz)
D = separation (Km)
Gt = transmit antenna gain (in the direction of the receive antenna).
Gr = receive antenna gain (in the direction of the transmit antenna).
For the UHF 450 MHz frequencies, the antenna isolation at 100 m separation is
approximately 65.6 dB for omni-directional antennas (0 dB gain). To increase
isolation, the antennas should have higher directivity and must be pointed away from
each other.
c. Occasional Drop-out of some Channels
Possible causes: One channel with very strong power dominates the RF output of the
amplifier.
d. Laser Alarm Occurs
Possible causes:
Fiber cable interface is not secure or dirty.
Take out each fiber cable and clean the connector and connector assembly with
alcohol or equivalent fiber cleaner, to make sure no dirt or dust inhibits the link
operation.
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