How to Configure N1MM with PowerSDR and VAC for Voice Keying

Content provided by: Mack, WB4MAK

The intent of this article is to describe in detail the setup and configuration of N1MM for voice keying with PowerSDR. The configuration of VAC’s parameters other than the audio and PTT are outside the scope of this article.

Configuration Overview and Required Software
In this procedure we are assuming that you have your software defined radio and PowerSDR properly communicating and are using the most current versions of PowerSDR. It is also assumed that you have VAC and your virtual COM port program properly configured. This procedure was developed using the FLEX-5000, so it is important that you have the latest Firewire driver and firmware loaded for your radio as well. It should work equally well on any Flex radio.

Step 1. Download and install the latest version of N1MM
You can download N1MM software from the N1MM Home Page . For this procedure, N1MM 10.10.2 was used.

Step 2. Download, install and configure a virtual com port software (Com0Com, VSPE or VSPmanager) for PTT Control
Although there are several different free software packages for enabling virtual com ports, I prefer to use VSPE because it support Win 7 x64 and is very fast. You can download the virtual com port software from the VSPE Home Page. For this procedure VSPE 0.938.4.846 was used. Any of the virtual port packages should work fine.

Step 3. Download, install and configure the Virtual Audio Cable software (VAC)
VAC is a program that transfers the TX audio from PowerSDR to N1MM and subsequently transfers the RX audio from N1MM to PowerSDR without using a physical interface between the radio and a computer sound card. VAC makes PowerSDR "look" like a sound card or Windows audio device to N1MM. The benefit of VAC is that the audio exchanged between PowerSDR and N1MM stays entirely in the digital domain resulting in high dynamic range signals and there are no wires to introduce RF into the software defined radio system.

VAC is not free open source software. It must be purchased from the authors web site. There is a demo version of VAC but it can not be used because the demo version corrupts the audio I/O with a pre-recorded voice telling you it is demo software, essentially making it crippleware. For this procedure, VAC 4.09 (4.90) was used.

Step 4. Configure PowerSDR to use VAC and VSPE to interface with N1MM
Once the required software is downloaded and installed on your computer, the next step is to configure PowerSDR to use the VAC virtual audio cable for audio transfer and to configure a PTT line so that N1MM can key the transceiver. For this procedure PowerSDR 1.14.15 was used.

Step 5. Configure the Audio and PTT ports in N1MM
The final step is to configure PTT control and the audio input and output connections for N1MM. This is probably the most confusing part of the N1MM configuration since the audio setup interface is very rudimentary.

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Step 1. Download and install the latest version of N1MM
Using the URL listed above in Step 1 of the Configuration Overview and Required Software section for the N1MM home page download and install N1MM.

Step 2. Download, install and configure a virtual com port software VSPE for PTT Control
If you are unfamiliar with the concept of virtual com port pairs that are sometimes called virtual null modem cables, you can refer to the Knowledge Center article, What is a virtual com port or null modem emulator? , for a detailed description of how virtual com port software works.

As noted above, in this example, VSPE virtual com port software is used. For this configuration only one pair is required. I have configured my virtual com port pair as 2/18. Ensure you configure VSPE to NOT assert RTS or DTR.


Step 3. Download, install and configure the Virtual Audio Cable software (VAC)
As noted above, you must purchase VAC as it is a commercial product. Using the URL listed above in Step 3 of the Configuration Overview and Required Software section for the VAC home page you can purchase your copy of VAC if you have not already done so. If you have VAC 4.x, but it is not version 4.09, you are entitled to get minor version upgrades. To get them, you must contact the company or software distributor from whom you purchased VAC from initially as the upgrades are not directly available from the VAC home page. This procedure has not been tested with the 3.x version of VAC and some older versions of VAC 4.x have been reported not to work for whatever reason.

The VAC package is distributed as a ZIP archive. Simply unpack it into an empty folder, run setup.exe application and follow the instructions displayed. If you are installing VAC for the first time, please review the readme.txt and vac.chm (Windows Help) files before installation. If you have already installed previous version of VAC 4.x, don't forget to uninstall it before installation.

Using the Knowledge Center article, How to Setup Virtual Audio Cable (VAC) 4.0x with PowerSDR 1.x , execute steps 1 through 3 for the instructions to configure the two (2) VAC audio cables. The instructions in the KC article represent a very "conservative" configuration. For the N1MM configuration, we will use a more optimized configuration but it will work with the conservative configuration.

Make the following changes:

1. Ms per Int = 5
2. Stream Fmt = Cable Range
3. BPS = 8 .. 16

Step 4. Configure PowerSDR to use VAC and VSPE to interface with N1MM
Using the same Knowledge Center article referenced in Step 3, How to Setup Virtual Audio Cable (VAC) 4.0x with PowerSDR 1.x , execute steps 4 through 6 of the instructions to configure the PowerSDR VAC Audio parameters.

Make the following changes:

1. Driver = MME
2. Virtual Audio Cable Setup (Input) = Virtual Cable 1
3. Virtual Audio Cable Setup (Output) = Virtual cable 2

NOTE: Do not worry about the TX and RX Gain (dB) values, those will be set later.


Configure PowerSDR to use a com port for external keying by configuring. PowerSDR will use the virtual com port 18 of the virtual comport pair 2/18.

1. Start PowerSDR and open the Setup form
2. Select the CAT Control tab.
3. In the PTT Control section, click on the drop down box and select the virtual com port of the virtual com port pair defied previously in a step above. In this example I used COM18.
4. Check only the DTR check box.
5. Check the Enable PTT check box.
6. Check on the Apply button and close the Setup form

Step 5. Configure the Audio and PTT ports in N1MM
First, we will set up the PTT port for N1MM.

PTT Port Configuration

1. Start N1MM
2. From the main N1MM window (GUI), left click on Config and choose Configure Ports, Telnet Address, Other
3. Check the CW/Other box that corresponds to the virtual serial cable pair that you set up previously. In this example check Com2.
   
   
4. Now left click on Com2 Set. Set DTR to PTT.
   
   
5. Audio Channel Configuration

Within N1MM left click on Config, and choose Configure Ports, Telnet Address, Other. Left click the Audio tab.

Configure as shown in the following screenshot.

1. 1 – Zero or Single Card
2. Select Device Line 1 (Virtual Audio Cable)
3. Select Input Line Line 2
4. Radio Input Port Line 1

To test the configuration, startup PowerSDR and N1MM in this manner

1. Start PowerSDR
2. Switch to LSB or USB mode and make sure VAC is enabled
3. Start N1MM
4. Using your preconfigured audio files (I use Audacity to record) configure N1MM Config select Change CW/SSB/Digital Function Definitions to point to your sound clips and map them to an F key on your keyboard.
5. Press one of your F-Keys that you previously defined and test that PowerSDR transmits the audio properly. You may enable MON within PowerSDR to monitor the audio on your signal.
6. Adjust the gain within PowerSDR VAC to the properly level.

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