User's Manual

Epoch-H (HP/HC) RF Repeater
User Manual V1.5
Advanced RF Technologies, Inc. Proprietary Document Page 21 of 60
2.3 Antenna Separation/Isolation
Separation between antennas is necessary to prevent oscillation.
Oscillation occurs when the signal entering the system continually re-
enters, 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.
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 Epoch-H has a maximum gain of 95 dB, it requires an
isolation of at least 108 ~ 110 dB.
Figure 14 - RF Repeater Oscillation