User's Manual Part 3

168 Mercury Reference Manual 05-4446A01, Rev. D
station (shown by a lit LINK LED on the front panel), then measure the
reported RSSI value. (
See “Antenna Aiming—For Directional
Antennas” on Page 156 for details.) If you cannot obtain adequate signal
strength, it might be necessary to mount the station antennas higher, use
higher gain antennas, select a different site, or install a repeater station.
To prepare the equipment for an on-the-air test, follow the general
installation procedures given in this guide and become familiar with the
operating instructions found in the
CHAPTER-2 TABLETOP EVALUA-
TION AND TEST SETUP on Page 21.
5.1.7 A Word About Radio Interference
The transceiver shares the radio-frequency spectrum with other services
and users. Completely error-free communications might not be achiev-
able in a given location, and some level of interference should be
expected. However, the radio’s flexible design and hopping techniques
should allow adequate performance as long as you carefully choose the
station location, configuration of radio parameters, and software/pro-
tocol techniques.
In general, keep the following points in mind when setting up your com-
munications network:
• Systems installed in rural areas are least likely to encounter interfer-
ence; those in suburban and urban environments are more likely to
be affected by other devices operating in the license-free frequency
band and by adjacent licensed services.
• Use a directional antenna at remote sites whenever possible.
Although these antennas may be more costly than omnidirectional
types, they confine the transmission and reception pattern to a com-
paratively narrow lobe, minimizing interference to (and from) sta-
tions located outside the pattern.
• If interference is suspected from a nearby licensed system (such as a
paging transmitter), it might be helpful to use horizontal polarization
of all antennas in the network. Because most other services use ver-
tical polarization in this band, you can achieve an additional 20 dB
of attenuation to interference by using horizontal polarization.
Another approach is to use a bandpass filter to attenuate all signals
outside the desired band.
• Multiple Access Point units can co-exist in proximity to each other
with no interference. The APs should be configured to operate in
TDD Sync Mode, where their transmissions are synchronized to
GPS timing.
See “Protected Network Operation using Multiple
APs” on Page 16. For additional isolation, separate directional
antennas with as much vertical or horizontal separation as is practi-
cal.
• The power output of all radios in a system should be set for the low-
est level necessary for reliable communications. This reduces the