2. The Graph Type submenu key shows the graph type of the active window. Press this key to change the type.
Constellation
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.
Constellation Diagram
Spectrum
The Spectrum view displays a graphical representation of power (dBm) vs. frequency. The Spectrum display gives an indication if there are interfering entities present that may degrade the bit error rate of the PTC 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: PTC-ACSES Spectrum Graph25kHz and 50kHz displays the same signal using a 25 kHz span and a 50 kHz span.
PTC-ACSES Spectrum Graph25kHz and 50kHz
Eye Diagram
The eye diagram is an oscilloscope view of the PTC signal displaying the voltage of the signal vs. time. The diagram provides an indication of baseband fidelity of a PTC 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.
PTC-ACSES Eye Diagram
Summary Table
The Summary Table provides an overview of a PTC-ACSES transmitter. The table displays received power or burst power, peak envelope power (PEP), frequency error, error vector magnitude (EVM), bit error rate (BER), IQ offset, phase error, magnitude error, and symbol rate error of the input signal.
The received power and PEP values in the Summary Table can be changed between dBm, watts, and volts using the Amplitude > Units > Rx Units submenu key. This setting also applies to the burst power and squelch level setting. Press the Power Display key to toggle between displaying the received power (continuous) or the burst power.
The Setup > Squelch Lvl submenu key sets the received power level below which Summary Table results are not displayed. When the received power is lower than the set squelch level, all measurement values except for received/burst power will be blanked out (--) in the summary table. When the received power is above the squelch level, the measurements will display as shown in Figure: PTC-ACSES Summary Table.
PTC-ACSES Summary Table
Received power in the Summary Table is the integrated power of all the energy in the receiver bandwidth. The reduction is specified as: 10*Log (Signal Bandwidth / Resolution Bandwidth). Burst power in the Summary Table is calculated only when the data stream contains packets and BER is calculated for each burst.
Message Decode Table
The Message Decode Table displays several items:
PTC-ACSES Message Decode Table
Source ACSES Address
This address is found either by parsing the payload searching for the Railroad ID (RRR) or derived from the Source Address location specified in the Setup Menu. The value displays in hex.
Source Type
The type is decoded from the Source Address identified by RRR.
Destination ACSES Address
This address is found either by parsing the payload searching for the Railroad ID (RRR), or derived from the Destination Address location specified in the Setup Menu. The value displays in hex.
Destination Type
The type is decoded from the Source Address identified by RRR.
Time Slot in frame
This slot is the time slot (1-8) within the current 1-second frame that contains the message being displayed.
Time Slot in epoch
This slot is the time slot (1-48) within the current 6-second epoch that contains the message being displayed.
Time-slots
Payload Table
The Payload Table Payload displays the contents of the 117-byte payload in hex format. The image below is 10 rows of 12 hex values (last row only has 9 hex values).
PTC-ACSES Payload Table
The number of rows and hex values within each row are flexible, allowing for font size and available space.
Message payload is also sent over the Ethernet, accessible by TeraTerm.
