FCC ID: OIW CBDASMRPS8
Page 9 of 10
DIAGNOSTICS GUIDE
As mentioned before the BDA should provide long term, care free operation
with no need of any periodic maintenance. This section will cover possible
problems that may show up after installation.
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
F is frequency in GHz
D is separation in Km
Gt is the transmit antenna gain (at the direction of the receive antenna).
Gr is the receive antenna gain (at the direction of the transmit antenna).
For example at the SMR frequency the antenna isolation at 100 m separation
is about 71 dB for omni 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 dominating the RF
output of the amplifier.
