Freedom R8100 SERIES, Operator'S Manual

Page: 182 / 255

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Bits Symbol Deviation ΔPhase
01 +3 +2250 Hz +135°
00 +1 +750 Hz +45°
10 -1 -750 Hz -45°
11 -3 -2250 Hz -135°
Table 2.2.7.9.1.2-1. HDQPSK Symbols
BER Test (P25 II submenu)
Start or Stop Bit Error Rate (BER) testing. 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 II submenu. BER test results are
shown as an error in % in the P25 II Zone – see Figure 2.2.7.9.1.2-1.
BER (P25 II Zone display)
See BER Test above.
2.2.7.9.1.3 Display Zone
Select Display (Display Zone submenu)
See 2.2.4 Display Zone for standard selections and below for custom selections.
Eye Diagram (Display Zone selection)
The Eye Diagram provides a visual display of the received signal and overlays the modulation response
during two symbol periods over the yellow “target” crossing points for an ideal signal – see Figure
2.2.7.9.1.3-1. The Eye Diagram can indicate whether a transmitter has significant unbalances or offsets in
the modulation circuitry by noting how tightly grouped the waveform is around the crossing points. Be
sure that the Modulation Type in the P25 II test zone is set for the expected receive signal in order to
establish the appropriate number of crossing points and symbol timing used to position the diagram on the
horizontal axis. The center of the display is at symbol times for HDQPSK but halfway between symbol
times for HCPM. Some overshoot caused by ISI is expected, more for HCPM. View the Eye Diagram
with the other P25 measurements on the main screen by selecting it in the Display Zone.