MDS 05-4055A01, Rev. A
MDS entraNET 900 System Guide (Preliminary)
109
tion, configuration of radio parameters and software/protocol tech-
niques.
In general, keep the following points in mind when setting up your com-
munications 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. 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, that 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 ver-
tical polarization in this band, an additional 20 dB of attenuation to
interference can be achieved by using horizontal polarization.
Another approach is to use a bandpass filter to attenuate all signals
outside the 900 MHz band.
4. Multiple Access Point units can co-exist in proximity to each other
with only very minor interference. Each network name has a differ-
ent hop pattern. (
See “Protected Network Operation through Multi-
.) Additional isolation can be achieved
by using separate directional antennas with as much vertical or hori-
zontal separation as is practical.
5. If constant interference is present in a particular frequency zone
(collection of 8 RF channels), it may be necessary to “skip” that
zone from the radio’s hopping pattern. The radio includes built-in
software to help users identify and remove blocked frequency zones
from its hopping pattern. (
See “Skip Zone Options Menu” on
6. If interference problems persist even after skipping some zones, try
reducing the length of data streams. Groups of short data streams
have a better chance of getting through in the presence of interfer-
ence than do long streams.
7. The power output of all radios in a system should be set for the low-
est level necessary for reliable communications. This lessens the
chance of causing unnecessary interference to nearby systems.
Summary of Contents for MDS entraNET 900
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