User's Manual

8 MDS TransNET I&O Guide MDS 05-2708A01, Rev. D
With the hand-held antenna positioned near the proposed mounting spot, a
technician can check for synchronization with the Master station (shown by
a lit SYNC lamp on the front panel) and measure the reported RSSI value. If
adequate signal strength cannot be obtained, it may be necessary to mount the
station antennas higher, use higher gain antennas, or select a different site. 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 given in Section 5.0, beginning on Page 19.
If time is short, and a site survey is impractical, a computer path study is a
good alternative. Factors such as terrain, distance, transmitter power, receiver
sensitivity, and other conditions are taken into account to predict the perfor-
mance of a proposed system. Contact MDS’ Technical Services Group for
more information on path study services.
3.3 A Word About Radio Interference
The radio shares the frequency spectrum with other services and other Part 15
(unlicensed) devices in the USA. As such, near 100% error free communica-
tions may not be achieved in a given location, and some level of interference
should be expected. However, the radio’s flexible design and hopping tech-
niques should allow adequate performance as long as care is taken in
choosing station location, configuration of radio parameters and soft-
ware/protocol techniques.
In general, keep the following points in mind when setting up your commu-
nications network:
1. Systems installed in rural areas are least likely to encounter interference;
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.
2. If possible, use a directional antenna at Remote sites. Although these
antennas may be more costly than omnidirectional types, they confine the
transmission and reception pattern to a comparatively narrow lobe, which
minimizes interference to (and from) stations located outside the pattern.
3. If interference is suspected from a nearby licensed system (such as a
paging transmitter), it may be helpful to use horizontal polarization of all
antennas in the network. Because most other services use vertical
polarization in these bands, an additional 20 dB of attenuation to
interference can be achieved by using horizontal polarization.
4. Multiple transceiver systems can co-exist in proximity to each other with
only very minor interference as long as they are each assigned a unique
network address. Each network address has a different hop pattern.
Additional RF isolation can be achieved by using separate directional
antennas with as much vertical or horizontal separation as is practical.
Vertical separation of antennas is more effective per foot/meter than
horizontal.