Specifications

05-4055A01, Rev. D GE MDS entraNET Reference Manual 151
some level of interference should be expected. However, flexible design
and hopping techniques should allow adequate performance, as long as
care is taken in choosing station location, configuration of radio param-
eters, and software or protocol 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
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.
• Use a directional antenna at remote sites whenever possible.
Although these antennas may be more costly than omnidirec-
tional types, they confine the transmission and reception pattern
to a comparatively narrow lobe, which minimizes interference
to (and from) stations located outside the pattern.
• 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 this band, an additional 20
dB of attenuation to interference can be achieved by using hor-
izontal polarization.
Another approach is to use a bandpass filter to attenuate all sig-
nals outside the desired band.
• Multiple AP radios can co-exist in proximity to each other with
only very minor interference. Each network address has a differ-
ent hop pattern. Additional isolation can be achieved by using
separate directional antennas with as much vertical or horizontal
separation as is practical.
• If constant interference is present in a particular frequency zone,
it may be necessary to “skip” that zone from the hopping pat-
tern. The radio includes built-in software to help you identify
and remove blocked frequency zones from its hopping pattern.
See “Skip Zones Menu” on Page 53 for more information.
• 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 interference than do long streams.
• The power output of all radios in a system should be set for the
lowest level necessary for reliable communications. This less-
ens the chance of causing unnecessary interference to nearby
systems.
If you are not familiar with these interference-control techniques, con-
tact your GE MDS Sales Representative or the GE MDS Technical Sup-
port Department for more information.