AE04B-A0279 Rev -- APPENDIX C: APPLICATION NOTES
Document use is restricted to that described on cover
C-1
APPENDIX C
APPLICATION NOTES
The Andrew SelectAmp800 is a two-way on-band repeater with two RF paths. One path is for connection to
an antenna directed towards the service providers base station (this would usually be a Yagi or some other
directional antenna). The other path is connected to an antenna or suitable leaky feeder cable directed over
the area in which the mobile units are to be found.
Typical applications for the amplifier are as follows:
1. Extending coverage to within tunnels. This is achieved by the use of a leaky feeder cable
running the length of the tunnel attached to the mobile port of the amplifier. A directional
antenna would be connected to the base port of the amplifier directed towards the base
station. In this way uninterrupted coverage can be extended to within the tunnel. In some
cases a Yagi or omni-directional antenna can be used.
2. Extending coverage to within buildings. Many modern buildings incorporate large amounts of
reinforced concrete and other metal in their construction and, therefore, act as effective
screens to penetration by RF signals. By using localized antenna or leaky feeders within
these buildings connected to the mobile port, and a Yagi on the top of the building connected
to the base port, coverage can be extended to within these buildings.
3. Local topology, e.g., hills, embankments, etc., can cause propagation blank spots. By using
a suitable antenna to cover the area and a Yagi mounted high enough to "escape" the blank
spot, coverage can be extended to these areas.
4. Temporary requirements for radio coverage can arise from such events as conferences,,
exhibitions, sporting events, etc. These short term events would not justify the expense of a
permanent base station. Therefore, an amplifier can be employed to "borrow" channels from
a less busy site some distance away that would otherwise be out of range of mobiles units at
the event.
5. If a site becomes heavily congested with radio traffic and a neighboring site is under-utilized,
an amplifier can be utilized to "borrow" channels from the quiet site for use in the coverage
area of the busy site.
6. In areas of low user density, a base station can be under-used. However, it is often
impossible to increase coverage from a central point which experiences limits on power
levels, mast heights etc. In these instances an amplifier placed some distance away from
the base station can be used to extend the coverage in a desired direction.
When siting the two antennas for an amplifier, the most important requirement is to maintain the RF isolation
