User's Manual

Axiom Repeater
User Manual V0.3
Page | 24
3.5.3 Antenna Separation/Isolation
Separation between the antennas is necessary to prevent oscillation. Oscillation
occurs when the signal entering the system continually reenters, due to the lack of
separation between the donor and server antennas. In other words, the signal is
being fed back into the system. This creates a constant amplification of the
same signal. As a result, the noise level rises above the signal level.
Figure 17: RF Repeater Oscillation
To prevent feedback, the donor and server antennas must be separated by an
appropriate distance to provide sufficient isolation. Isolation is attained by
separating antennas a sufficient distance so that the output of one antenna does
not reach the input of the other. This distance is dependent on the gain of the
repeater.
A sufficient isolation value is 13 ~ 15 dB greater than the maximum gain of the
repeater. For example, if the gain of the repeater is 50 dB, then an isolation of 63
~ 65 dB or greater is required. In the same manner, because the Axiom has a
maximum gain of 80 dB in case of Axiom 25K, it requires an isolation of at least
93 ~ 95 dB.