Instruction Manual

Fusion Installation Procedures
7-26 InterReach Fusion Installation, Operation, and Reference Manual
CONFIDENTIAL D-620TBD-0-20 Rev A
these situations is to provide sufficient isolation by physically separating the interfer-
ing transmitters and receivers.
iDEN occupies spectrum at both 800 MHz and 900 MHz (Tx:806–825/Rx:851–870
and Tx:896–901/Rx:935–940), while the Cellular A and B carriers share a single 850
MHz block (Tx:869–894/Rx:824–849). The combination of these frequency bands,
800/900 MHz iDEN and 850 MHz Cellular, result in uplink (BTS receive) bands that
are adjacent to downlink (BTS transmit) bands. Figure 7-5 depicts these nearly con-
tiguous bands, with arrows indicating the interfering downlink and receiving uplink
bands.
Figure 7-5 800/850 MHz Spectrum
Installation of an in-building distributed antenna system (DAS) to provide coverage
for both 800/900 MHz iDEN and 850 MHz Cellular must account for these down-
link-to-uplink interference issues and provide adequate isolation.
LGC offers the following guidelines toward achieving the proper amount of isolation
when deploying LGC Wireless Unison DAS products.
Figure 7-6 Guideline for Unison RAU Antenna Placement
800 MHz iDEN Downlink and 850 MHz Cellular Uplink
A 2 MHz frequency gap (851 – 849 MHz) separates the 800 iDEN downlink and 850
Cellular uplink frequency bands. Because of this narrow spacing, 800 iDEN down-
link intermodulation products may fall within the 850 Cellular uplink band. In addi-
tion, 800 iDEN downlink signals near the lower edge of the band at 851 MHz may
cause the 850 Cellular uplink automatic level control (ALC) circuitry in the RAU to
engage and thereby reduce uplink gain.
850
850