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The signal strength is shown in the Received Signal Strength
Indication (RSSI) field in the leftmost lower corner of the beltpack’s
display. The error rate is shown in the ERR field in the middle of the
display.
Figure 9-1: A Beltpack’s Site Survey Screen
• The RS (signal strength) number will fluctuate, ranging from 0 to
55, as the user walks through the coverage area, and may even
fluctuate as the user stands still. As a rule-of-thumb the best
system performance will be obtained when the signal strength
remains at 30 or above. If the signal strength falls below 30 the
beltpack may start losing audio. This is the limit of the coverage
zone.
• The ERR (error rate) number indicates packets of audio which are
lost or corrupted. When this number exceeds a few percent the
user may start hearing audible audio breakup.
• A high Received Signal strength indication and a high Error rate
may indicate that there is another RF system causing
interference.
A beltpack can transmit to an antenna outdoors at an average
distance of 125 meters when the beltpack has an unobstructed
“line-of-sight” path to the antenna. In ideal conditions, the range may
be as high as 250 meters. Indoors, a beltpack can transmit to an
antenna at an average distance of 50 meters.
6. Draw a map of the coverage zone for the antenna. The coverage
zone is the area where the signal strength, as a rule-of-thumb, is 30
or above and the error rate is below a few percent.
7. Repeat this process, one antenna at a time, for as many antennas
as necessary to cover the required area. Overlap coverage zones
so that there is no area where the signal strength is below 30, and
no area where the error rate is above a few percent.
9-4
Clear-Com Communication Systems
CellCom V2.0 Instruction Manual