Remote Operation via the Internet for PowerSDR 1.x

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Remote Operation via the Internet for PowerSDR 1.x

Remote Operation via the Internet for PowerSDR 1.x

  System Dependencies
  Minimum PowerSDR Version:     1.6.2 
  Applicable Hardware:     Any transceiver 

Content provided by: Mark, N6SF

Remote operation often brings images of remote mountain sites with large antennas, a pad locked shack and no one around for miles. But remote operation can also be very useful and fun inside your home QTH. Remote operation using a Wi-Fi connected laptop with a computer headset frees you from the shack and allows you to monitor and have QSOs from your living room, bedroom or even relaxing out by the pool (assuming you have one).

This paper focuses primarily on how to setup a simple remote audio link with FlexRadio Transceivers, but is applicable to any SDR that use PowerSDR 1.x. When combined with remote rig control, you can quickly experience the thrill of remote operation whether the rig is on that remote mountain top or in the next room.

The FlexRadio team is currently revising portions of the PowerSDR code. One of the goals of this effort is to provide integrated remote control operation including audio. While this will address remote operation, it will take some time before it is ready for prime time. Until then, we have several options for remoting the audio for use with PowerSDR.

The Remote Audio Connectivity for PowerSDR and the SDR-1000 document and W5SXD’s Introduction for Introduction for Configuring the SDR-1000 for Remote Operation KB article both discuss how to interface a separate sound card to the SDR-1000 for remote audio. However, since this is a software defined radio it seemed there should be a software way to do this.

VAC (Virtual Audio Cable) is commonly used by PowerSDR 1.x to connect the radio to digital mode software such as MixW. So why not use VAC to connect PowerSDR to a VoIP (Voice Over IP) program? There are two major advantages to this approach. First, it eliminates the need for special cabling with possible RFI issues. Second and more significantly, it eliminates the need for a second sound card all together.

VAC has been successfully used with two VoIP programs. The first success was with IP-Sound. More recently settings were found that work with Skype. In the remainder this document the setup, usage and limitations for remote audio using these programs is described.

PowerSDR and VAC
For reasons explained later, the official release of PowerSDR version v1.6.2 or later is strongly recommended. So please update to this version or newer. See the SVN guide on the FlexRadio Systems Download page for information about using SVN.

If VAC is not already installed on your SDR computer, install this program. Examples of how to install VAC can be found in the KB articles How to Setup Virtual Audio Cable (VAC) 4.0x with PowerSDR 1.x  and Optimizing the SDR-1000 for Weak Signal Operations on Two Meters. Unfortunately VAC is not a free program.

IP-Sound Installation
IP-Sound was developed by Christopher Svenstedt, SM5VXC, to provide acceptable audio quality with low latency over IP networks specifically for applications like ham radio. Some versions of IP-Sound even integrate remote ICOM control.

Figure 1 IP Sound

IP-Sound allows selection of the input and output sound devices and has other useful features including auto answer, multiple codecs, a built-in test feature, settable bandpass filters and the ability to restrict access by IP address or an authentication key. The program is free and there is a forum for support.

SDR Computer Setup
Download IP-Sound from and install on both the SDR PC and the remote (client) computer.

On the SDR computer right click near the top of the IP-Sound window and select Tools/Properties. On the Network tab the computer’s IP address should already be displayed. The port used for UDP packets is settable with 4444 as the default. Enter a handle (name) to identify this computer as shown in Figure 2.

Figure 2 IP Sound Properties

Now select the Sound tab and set the input and output ports to match up with the settings on your PowerSDR VAC tab as in the example shown in Figures 3 and 4. Also select G711 uLaw 8kHz as the codec.

Figure 3 IP Sound - Sound Settings

Figure 4 PowerSDR VAC Settings

Be sure the “Enable VAC” box is checked. The “Stereo” box should be unchecked and “Sample Rate” should be set to 8000.

In IP-Sound, check the “Auto Answer” box under the Access tab. This is also where access can be restricted by IP address or an authentication key.

Figure 5 IP Sound - Auto Answer Remote Computer Setup

To configure IP-Sound on the remote computer right click near the top of the IP-Sound window and select Tools/Properties. On the Network tab enter a handle (not the same one as on the SDR computer) and a port if the default is not usable. The port does not need to be the same port as on the SDR computer. If desired “Connect to this client at start” can be set after the SDR client is added in the next step.

Right click and select Client/Add. Enter the IP address and the name of the SDR computer. IP-Sound can also be setup to do a DNS query if the SDR computer is DNS resolvable. Click Add to save this entry.

Figure 6 IP Sound - Client

Under the Sound tab “system” should be selected as both the input and output audio ports unless the default audio card is not being used for the speaker and mic. Select G711 uLaw 8kHz as the codec.

Figure 7 IP Sound - Client Audio Setup IP-Sound Operation

Start PowerSDR and IP-Sound on the SDR computer and IP-Sound on the remote computer. On the remote computer click the green arrow on the lower right if auto connect on startup was not selected. The arrow should turn yellow and name of the SDR computer along with other information will be displayed.

Figure 8 IP Sound - Operational

The green line next to the speaker symbol will show if audio is being received from the SDR computer. On the SDR computer the line next to the mic symbol will show if audio is being sent to the remote computer. Similarly on the remote computer the line next to the mic symbol will show if mic audio is being sent. On the SDR computer this audio will show next to the speaker symbol.

Click the upper of the two small yellow boxes in the window to see an audio scope view as shown in Figure 9. This scope responds to audio in either direction.

Figure 9 IP Sound - Scope

There are multiple gain settings in the paths between the mic and speaker on the remote computer and the SDR-1000. Some experimentation will be required to set the proper levels. Note that the volume sliders in the IP-Sound window often do not seem to work. Also, keep in mind that the AF setting on PowerSDR does not affect the receive audio since VAC is fed with a constant level. To adjust levels on the SDR the Gain controls under VAC setup should be used instead. Also the Mute button only mutes the local audio not the VAC audio.

Skype Setup

The setup of Skype setup is very similar to that of IP-Sound. Install Skype on both the SDR and Remote computers. Please refer to the Skype site for download and Skype basic setup.

After you have confirmed Skype is working on the standard audio ports, set Skype on the SDR computer to connect to the VAC ports using “Audio In” and “Audio Out” under Tools/Options/Sound Devices. “Ringing” should be left with the default device. The various notification sounds can be disabled from the “Sounds” window.

Figure 10 Skype Sound Devices

Next under Tools/Options/Advanced set Skype to start with Windows and to automatically answer incoming calls.

Figure 11 Setting Auto Answer in Skype

Access to the Skype can be controlled by setting the appropriate options under Tools/Options/Privacy as shown in Figure 12.

Figure 12 Skype Privacy Settings

For use with Skype the PowerSDR VAC “Sample Rate” must be set to 48000 and the “Stereo” box must be unchecked.

Figure 13 PowerSDR VAC Settings for Skype Networked Audio Limitations

One disadvantage to linking all these software programs together is that each has its own buffering and thus each delays the audio stream. The sum of these delays can approach 1 second in each direction even over a local area network. The buffer settings in PowerSDR’s VAC and under the Sound tab in IP-Sound should be reduced to the minimum level that still provides uninterrupted audio (Skype does not provide buffer setting options). Even then, the operator must be aware of the delay. For example, releasing the PTT as soon as you finish speaking is guaranteed to cut off at least a syllable or two. Timing in pileups can also be a challenge.

Both Skype and IP-Sound were designed to support basic communications audio over an IP network; high quality audio was not a design goal. However, IP-Sound does list various codecs. So far G711 uLaw 8kHz has provided the best quality for IP-Sound. Higher rate codecs which would be expected to provide higher quality have resulted in distorted audio. Further testing is need in this area. In order to interoperate the “Sample Rate” and “Mono/Stereo” fields for PowerSDR must match the IP-Sound codec selection. In some PowerSDR versions before v1.6.2 SVN: 537 changing these setting while the transceiver is ON will cause PowerSDR to crash and hang.

It is possible to monitor your audio remotely by clicking the MON button. However, this is only useful for testing as the round trip delay to the radio and back makes speaking difficult. This is in fact the reason earlier versions of PowerSDR are not recommended. In versions earlier than SVN 478 incoming VAC audio was always reflected back onto VAC regardless of the MON setting.

When returning to local operation, be sure to turn off “Enable VAC”. While in VAC mode, receive audio is delivered in parallel to both the local sound card and VAC but transmit audio only comes from the VAC connection and not from the local mic.

Occasionally, particularly during program startup, you may find things don’t work together and it is necessary to restart programs or even reboot the SDR computer to get things going again. This should not be an issue as any control operator of a remotely controlled station must have the ability to regain control of his station to meet FCC requirements.

Operation over the Internet has not yet been tested. However, other than even longer audio delays little change would be expected when using high speed connections on both ends.

Transceiver (Hardware) Control in Local Networks
In a local high speed environment MS Remote Desktop is recommended to access the SDR computer. This gives a full screen view of the SDR computer display and even allows viewing of the Panadapter in near real-time. Remote Desktop is usually preinstalled on Windows XP, if you do not have it, it can be downloaded from

For more remote operations, programs such as Ham Radio Deluxe ( can be used to manage the SDR. Other methods for remote operation and station management are described in the Flex Expert Setup paper “remote ops”.

Remote rotor control is also simple to setup for most modern rotors. Start with the free LP-Rotor program by Larry Phipps, N8LP at

Both Skype and SM5VXC ‘s IP-Sound programs when combined with VAC makes networked remote audio to PowerSDR easy to setup and eliminates the need for additional hardware.

The enhancements being planned for the PowerSDR will certainly make remote operation more convenient and reliable but there is no reason to wait. You can be “always connected” to your software defined radio today.

This KB article may reference additional files that are available on the FlexRadio Systems web site Downloads page. Please use the URL(s) below to download the referenced materials.

An Adobe Acrobat Reader may be required to open the file. You can download Adobe Acrobat from here.

KB Source Document(s):

Remote Audio Connectivity for PowerSDR and the SDR-1000 

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Last Modified:Saturday, August 2, 2008
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