Antenna Separation/Isolation; Figure 4-3 Rf Repeater Oscillation - ADRF SDR-ICS-43 User Manual

4.3

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.
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.
With ICS enabled, the recommended isolation value is 5dB greater than the maximum gain of the repeater.
For example, if the gain of the repeater is 50 dB, then an isolation of 55dB or greater is required. In the same
manner, because the SDR-ICS-43 has a maximum gain of 95dB in case of SDR-ICS-43, it requires isolation of at least
100dB.
With ICS disabled, the recommended isolation value is 20dB greater than the maximum gain of the repeater.
For example, if the gain of the repeater is 50 dB, then an isolation of 70dB or greater is required. In the same
manner, because the SDR-ICS-43 has a maximum gain of 95dB in case of SDR-ICS-43, it requires isolation of at least
115dB.
Advanced RF Technologies, Inc.
Figure 4-3 RF Repeater Oscillation
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