| System Dependencies | |
| Minimum PowerSDR Version: | 1.18.0 |
| Applicable Hardware: | Any FlexWire enabled hardware |
Content provided by: Steve, N5AC/AAR6AM
The following KC article will describe how to interface a PTC-IIpro Pactor Modem running PACTOR III. The FLEX family of SDRs are particularly suited for PACTOR III and the FLEX-3000 has achieved Speedlevel 6 (SL6) due to the superior IMD3 capabilities of the FlexRadio 3000 since PACTOR III is a multi-carrier protocol.
Hardware Interface
Below is a graphical representation of the connections between the FLEX SDR, the PC and the PTC-IIpro Pactor Modem using the FLEX-3000. The same basic connections are required for the FLEX-5000 as well
.The PTC-IIpro modem requires three connections to a HF transceiver:
- AF Input
- AF Output
- PTT
.The FlexWire interface cable should be available for Farallon Electronics if you do not want to make your own. Please contact them directly for cable availability.
In addition to the PTC-IIpro Modem-to-FLEX SDR connections, to complete the hardware interface for the PACTOR/SDR system you need the PTC-IIpro Modem-to-PC serial connection, using either a serial (RS-232), a USB or a Bluetooth connection depending on the model of PTC modem you have purchased. Please refer to the Pactor Modem for detailed information for interfacing the modem to the PC. The final connection is the control and audio interface between the FLEX SDR and the PC, which is a 1394a Firewire connection fo the FLEX-5000 and FLEX-3000.
PowerSDR Configuration
There are several PowerSDR configuration parameter that need to be set before the PTC-ProII modem will work properly. Please refer to the PowerSDR 1.x configuration settings listed below as a guide for configuring the PTC-IIpro Pactor modem.
Mode
It is best to use the DIGx operating modes since in these modes, there is no signal processing applied to either the RX or TX audio streams. NOTE: VAC is not being used for the PTC-IIpro configuration (The physical FlexWire inter is being used), so if you have VAC auto enabled for digital mode, un-check this option.
Buffers & Sampling Rate
The critical operating characteristic is to get the lowest latency and fastest T/R turn around times for proper PACTOR operation. Since the PTC modem, itself, has internal DSP and compensates for its own delay, the use of large PowerSDR buffers is not necessary for PACTOR use. This includes the PowerSDR TX and RX DSP buffers along with using the smallest audio and Firewire buffers as well. Additionally, you want to use the highest sampling rate to minimize latency.
Reduce the DSP buffer size for the Digital mode down to 512 for both TX and RX. This configuration has been tested and works well, but depending on your particular operating environment you may want to raise these slightly if audio drop outs are observed and heard. Being able to run smaller buffers at a higher sampling rate means more time spent by the computer transferring buffers (this requires more CPU as the CPU is busy transferring buffers). Therefore using the FLEX SDRs to operate PACTOR requires a fast PC to achieve high sampling rates and small buffer configurations in addition to running software in conjunction with the Pactor II modem, such as Airmail.
Audio Configuration
Since the audio from the PTC-IIpro modem is coming in through the FlexWire connector, you will need to configure PowerSDR to use audio input and output from the FlexWire interface. Select FlexWire In as the input audio using the PowerSDR Mixer controls. You will also need FlexWire Out selected, but it should already be selected by default. You will use the audio gain controls in the PowerSDR Mixer. As for setting up TX levels, you want to select the "mic" option on the TX Meter drop-down box. The PTC-IIpro has a test signal it can generate. Use that for setting up levels. You want to adjust the level out of the PTC-IIpro and the input level in PowerSDR to produce as close as possible to 0dB on the Mic level meter without going over.
CAT Port
The PowerSDR CAT interface is needed by the controlling program, like Airmail to control the SDR. Setting up the CAT interface for PowerSDR requires defining a virtual comport pair using a program such as Com0Com. Please refer to the following KC article, Com0Com Installation and Configuration Guide for detailed instruction on how to install and configure Com0Com. Once the com port pair is defined, you will need to configure PowerSDR for CAT Control operation. Refer to the KC article, How to Configure CAT to Communicate with Third-Party Programs - Introduction for detailed information on how to configure PowerSDR to use a CAT interface. For Airmail, select 57600 for the baud rate for fast data transfer of the CAT commands and responses. In the example below, Comport pair COM20<->COM21 was used for configuring the CAT Control interface in PowerSDR.
Airmail 3.x Setup
This KC article will not go into any detail in regards to configuring Airmail for HF operation as that is well documented else where on the Internet. Just Google "Airmail HF configuration" for more information.
The one point that does need to be made regarding CAT configuration within Airmail, is to make sure you configure the CAT interface in Airmail to use the Kenwood protocol since Airmail does not support the native FLEX CAT protocol.
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