User Manual

DIAGNOSTICS GUIDE
The Mini-BDA provides long term, care-free operation and requires no periodic
maintenance. There are no user-serviceable components inside the Mini-BDA.
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
antennas.
b. Excessive Intermodulation or Spurious
Possible causes:
Amplifier oscillation caused by insufficient isolation. The isolation between two
antennas 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 SMR frequencies, the antenna isolation at 100 m separation is about 71 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.
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