How Much Output Power Can Be Used; Conducting A Site Survey; A Word About Radio Interference - GE MDS iNET Series Reference Manual

4.1.6 How Much Output Power Can be Used?

The transceiver is normally supplied from the factory set for a nominal +30 dBm (+29 dBm for iNET-II)
RF power output setting; this is the maximum transmitter output power allowed under FCC rules. The power
must be decreased from this level if the antenna system gain exceeds 6 dBi. The allowable level is depen-
dent on the antenna gain, feedline loss, and the transmitter output power setting.
NOTE:
In some countries, the maximum allowable RF output may be limited to less than the figures
referenced here. Be sure to check for and comply with the requirements for your area.

4.1.7 Conducting a Site Survey

If you are in doubt about the suitability of the radio sites in your system, it is best to evaluate them before a
permanent installation is underway. This can be done with an on-the-air test (preferred method); or indi-
rectly, using path-study software.
An on-the-air test is preferred because it allows you to see firsthand the factors involved at an installation
site and to directly observe the quality of system operation. Even if a computer path study was conducted
earlier, this test should be done to verify the predicted results.
The test can be performed by first installing a radio and antenna at the proposed Access Point (AP) station
site (one-per-system). Then visit the Remote site(s) with another transceiver (programmed as a remote) and
a hand-held antenna. (A PC with a network adapter can be connected to each radio in the network to simulate
data during this test using the PING command.)
With the hand-held antenna positioned near the proposed mounting spot, a technician can check for syn-
chronization with the Access Point station (shown by a lit
reported RSSI value. (See "Antenna Aiming" on Page 115 for details.) If adequate signal strength cannot
be obtained, it may be necessary to mount the station antennas higher, use higher gain antennas, select a
different site or consider installing 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 "Embedded Management System" on Page 14.

4.1.8 A Word About Radio Interference

The transceiver shares the radio-frequency spectrum with other 900 MHz services and other Part 15 (unli-
censed) devices in the USA. As such, near 100% error-free communications may not be achieved in a given
location, and some level of interference should be expected. However, the radio's flexible design and hop-
ping techniques should allow adequate performance as long as care is taken in choosing station location,
configuration of radio parameters and software/protocol techniques.
In general, keep the following points in mind when setting up your communications 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 omnidirectional types, they confine the transmission and reception pattern to a compara-
tively narrow lobe, that 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 horizontal polarization. Another approach is to use a bandpass filter to attenuate all signals out-
side the 900 MHz band.
• Multiple Access Point units can co-exist in proximity to each other with only very minor interference.
Each network name has a different hop pattern. (See "Protected Network Operation using Multiple
112 MDS iNET Series Reference Manual
LINK LED on the front panel) and measure the
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