User's Manual

VHF Headstation & In-Line Amplifiers
User Handbook
Handbook Nō.-50-127201FCC Issue No:-A
Date:-14/06/2005
Page:-
36 of 45
5. INSTALLATION & COMMISSIONING
5.1 Initial Installation Record
When this equipment is initially commissioned, please use the equipment set-up record sheet
in Appendix A. This will help both the installation personnel and AFL should these figures
be needed for future reference or diagnosis.
5.2 Antenna Installation & Gain Calculations
1 Most Cell Enhancer require two antennas, one a highly directional Yagi or similar
directed towards the donor cell base station, and one a leaky feeder, omni-directional antenna
or Yagi to cover the area in which the mobiles are to be served.
2 The maximum gain at which the Cell Enhancer can be set is limited by the isolation that
can be achieved between these two antennas. Therefore when the antennas have been
installed, inject a signal (at a known power level) into one of them and measure the signal
level received by the other antenna on a spectrum analyser. The isolation can then be
calculated as the difference between these two figures. The gain in each path of the Cell
Enhancer should be set at least 10 dB below this figure, using attenuators as described below
in paragraph 5.
3 Also measure the received signal from the donor cell at the input to the Cell Enhancer
(base port). The gain of the Cell Enhancer downlink path should be set such the donor site
will not overload the Cell Enhancer amplifiers. It is recommended that the input level should
be less than -50dBm at the input of the Cell Enhancer (Base Port). (This figure is assuming
maximum gain, and may be increased by the value of the attenuator fitted in the downlink
path.)
4 Ensure that the mobile facing antenna has at least 70 dB isolation from the nearest mobile.
(This is usually easily achieved when using a leaky feeder.)
5 The Cell Enhancer gain is set by setting the attenuation in each path (uplink and
downlink) between the first two amplifier stages (see markings within the Cell Enhancer or
layout drawings for the exact attenuator locations). Note that the uplink (mobile to base) and
downlink (base to mobile) path gains are set independently. This allows the paths to have
different gains if required to set the correct output power levels.
6 It is recommended that the gains are set such that the Downlink channel output levels
from the Cell Enhancer are typically +30dBm per channel
(Input level + Gain = Output level).