User's Manual

11
Part Number: J24004
Drawing Control: JD16049
SET UP AND INSTALLATION CONSIDERATIONS
BEFORE APPLYING AC POWER:
Make sure antennas are connected or the RF terminals are terminated!
Make sure amplifier is vertically mounted!
Antenna isolation must be 80 dB or greater to prevent oscillation!
Check the incoming spectrum to assure that no signals in the pass band are greater then -15 dBm!
ANTENNA ISOLATION
Proper implementation of the antennas is absolutely crucial to the repeater system. Several important issues must be
considered when selecting and implementing the antennas. The most important consideration, besides the obvious
concerns for gain and area of coverage, is the antenna isolation.
Base station to service area antenna isolation should be 80 dB. If the isolation is less, then gain ripple due to
feedback is likely. Positive feedback sufficient for oscillation will overdrive one or both amplifier links and may
eventually cause damage to the BDA.
High-gain (high directivity) antennas usually have significant isolation between front and back. Additional
decoupling can be achieved by spatially separating the antennas. Generally, for in-building applications, with one
antenna located outside and the other antenna located inside, the isolation is adequate. An isolation measurement is
always recommended when possible.
The most direct way to measure the isolation is to inject a known signal into one antenna, and measure the coupled
signal at the other antenna. This should be done across the applicable bandwidth to account for the frequency
dependency of standing waves. Ordinarily, reciprocity would dictate that measuring the isolation between antenna 1
and antenna 2 is the same as the isolation measured between antenna 2 and antenna 1. However, the reflection paths
for each antenna are likely different; therefore, the isolation measurements should be repeated in each link.