The following P25 Analyzer measurements are available on the LMR Master. From the Measurements main menu, press P25 Analyzer twice. Press the Graph Type submenu key to select the measurement type.

Constellation view displays the demodulation information in an IQ format (Figure: Constellation Diagram). The chart shows the relationship between the location of a constellation data point, its deviation frequency, and the information it carries.

Figure: Linear Constellation Diagram shows the same information in the Linear Constellation View.

For input signals that are not P25 encoded, the LMR Master will still try to decode it and fit it to a symbol. This may cause some measurement results that are unexpected.

The Histogram graph displays a graphical representation of the symbols that are being received. The graph for each symbol represents the relative percentage that symbol was identified out of all the received symbols.

Each update of the screen is a separate representation of the latest data, rather than a cumulative total. The vertical scale is fixed at 0 % to 100 %, with each horizontal grid line representing 10 % of the total symbols received.

The spectrum view displays a graphical representation of power (dBm) versus frequency. The spectrum display gives an indication if there are interferers present that may degrade the bit error rate of the P25 signal. The frequency span is adjustable under the Frequency menu. The reference level is adjusted with the Amplitude menu. Refer to Amplitude Menu for details. Figure: P25 Spectrum Graph (25 kHz Span and 500 kHz Span) displays the same signal using a 25 kHz span and a 500 kHz span.

The eye diagram is an oscilloscope view of the P25 signal displaying the voltage of the signal vs. time. The diagram provides an indication of baseband fidelity of a P25 transmitter. With Over‑the‑air measurements, the Eye Diagram can indicate phase distortion from multipath. The number of “eyes” displayed is set with the Symbol Span key under the Display Menu.

The summary graph provides an overview of a P25 transmitter. The graph displays numeric values of received power, frequency error, modulation fidelity (Mod Fid), bit error rate (BER), symbol deviation, Network Access Code (NAC), symbol rate error of the input signal and Signal-to-Interference-plus-Noise Ratio (SINR) when the input signal is control channel.

The Received Power value in the summary graph can be toggled to dBm, watts, or volts by using the Amplitude > Units > Rx Units submenu key. This setting also applies to the squelch level setting.

The Setup > Squelch Lvl submenu key sets the squelch power level. When the Received Power is lower than the set squelch level all summary graph measurements except for Received Pwr will be blanked out (--). When the Received Power is above the squelch level the measurements are displayed as shown in Figure: P25 Summary Graph with Received Pwr Above the Squelch Level.

Received Pwr in the Summary table is the integrated power of all the energy in the receiver bandwidth. Any peak amplitude reduction seen in the Spectrum display when compared to Received Pwr is a function of the instrument’s RBW setting. The reduction is specified as: 10*Log(Signal Bandwidth / Resolution Bandwidth).