Freedom R8100 SERIES, Руководство оператора

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Symbol Deviation (P25 Zone display)
P25 radios broadcast voice and data using a 4 level frequency deviation of the carrier to represent symbols
containing data bits as shown in the table below. The nominal deviation value for a Project 25 radio using
C4FM modulation is 1800 Hz. Since the deviation of a Project 25 C4FM signal is data dependent, that
aspect is factored when measuring overall carrier deviation. The Symbol Deviation field provides the
deviation measurement at symbol decision times.
Bits Symbol Deviation
01 +3 +1800 Hz
00 +1 +600 Hz
10 -1 -600 Hz
11 -3 -1800 Hz
Table 2.2.7.3.1.2-1. P25 Symbols
Symbol Rate Error (P25 Zone display)
The symbol rate error is a measurement of the transmitter symbol rate accuracy, the difference of the
actual minus the ideal. Thus a positive error indicates that the transmitter clock is too fast. P25 standard
TIA-102.CAAB-B 3.2.17 Symbol Rate Accuracy states that the symbol rate error shall not exceed 10
PPM which is +/- 48 mHz given the ideal symbol rate of 4800 baud. The measurement is designed to
provide much better accuracy by continually refining the measurement over time. A Reset Symbol Rate
Error soft key is provided to restart the measurement.
Reset Symbol Rate Error (P25 Zone submenu)
The Symbol Rate Error measurement is restarted. This is necessary after the input signal changes, i.e. is
discontinuous from when the measurement was started.
BER Test (P25 submenu)
Start or Stop Bit Error Rate (BER) testing in the P25 mode of the R8100. When performing the BER test
the radio transmitter under test must be placed in a test diagnostic mode using the manufacturer’s Radio
Service Software (RSS). The transmission is compared against the Test Pattern specified in the P25
submenu. BER test results are shown as an error in % in the PROJECT 25 Zone – see Figure 2.2.7.3.1.2-1.
BER (P25 Zone display)
See BER Test above.
Voice Loopback (P25 submenu)
This menu selection enables the Voice Loop feature in P25 mode (U.S. patent 5703479). Once enabled
the R8100 automatically records voice channel data when the radio under test transmits a signal above the
squelch level setting. A green Voice Playback Active indicator appears in the test mode zone when Voice
Loopback is enabled on the Voice Loopback screen – see Figure 2.2.7.3.1.3-3. The Record Duration
setting determines the maximum length of the recording and a bar graph meter shows the recording’s
progress – see Figure 2.2.7.3.1.2-2. The recording continues if the transmission is longer than the duration,
but only the most recent is retained. When the radio is un-keyed the R8100 automatically switches to
Generate mode and transmits the captured voice channel information or speech back to the radio – see