RF Troubleshooting Tools
35
Invalid Data
The lower graph, channel 2, of
Figure 4
, shows the
number of invalid data packets received. Note that the
invalid data is graphed logarithmically.
Invalid data packets are graphed as a function of time.
The graph shows the amount of invalid data packets
(shown by the amplitude or height of the spike) and the
duration of time the invalid packets are received (shown
by the pulse width of the spike). The invalid packets are
graphed using the bottom 3 boxes on the strip recording,
and are measured in seconds of invalid data per minute
of monitoring.
Any spikes that remain in the bottom box indicate a low
percentage of invalid data packets received and indicates
good performance for a receiver. As the amplitude of the
spikes increase, the higher percentage of invalid data
packets have been received. Spikes that reach the top of
the third box, indicate an entire minute's worth of invalid
data packets received.
Expected Performance
•
Mean Signal Strength of about -60 dBm (192 counts)
is expected
•
Dropouts are likely to occur if the signal strength
drops below -87 dBm (128 counts)
•
Signal strength “fades” of 30 dB are expected.
•
Good noise floor measurement would be about -100
dBm (90 counts)
quickref.fm Page 35 Wednesday, June 5, 2002 3:08 PM
