For getting started with Ham Radio Sound Card digital modes. Jeffrey Kopcak K8JTK
Table of Contents Introduction... 3 Program versions... 3 Resources... 3 SignaLink... 3 Rigblaster... 3 Configuration... 4 Playback settings... 4 Recording settings... 10 Testing and troubleshooting... 15 Transmit... 15 Receive... 17 Recording with Audacity... 19 Recording settings... 21 Record all received and transmitted audio... 22 Timer recording... 23 Saving... 25 Playback... 26 Sound card clock calibration... 29 Page 2 of 29
Introduction This document will demonstrate basic setup of a radio interface device in the Windows Sound Control Panel to use with Ham Radio Sound Card digital modes. Programs include: Ham Radio Deluxe DM780, MMSSTV, Fldigi, wsjtx, FreeDV, Easypal. In addition, it will demonstrate how to record digital transmissions and play them back. This is written with the beginner in mind and many concepts outlined step-by-step. It will provide direction for further experimentation on your own or on the net and direction for troubleshooting. The SignaLink USB was used but these instructions can be adopted for similar devices. Those using other methods may find the settings and techniques useful. It is important to note: plugging the same device into a different USB port will be recognized as a new device by the system. This means the audio settings will need to be re-configured. In addition, the audio device settings in the digital mode program may need to be re-configured as well. Prepared for The Lake Erie Amateur Radio Association s Digital Net (http://www.leara.org/). Program versions Windows 7 64 bit Audacity 2.0.6 Resources Still having trouble after using this tutorial? Read through the product manual and support documentation. Below are links for popular devices. Specific instructions can be found online typically by searching: [name of application] [radio interface device]. Example: Fldigi SignaLink USB. SignaLink Homepage: http://www.tigertronics.com/ General support, operating tips, manuals, and modifications (all models): http://www.tigertronics.com/sl_suprt.htm SL USB troubleshooting: http://www.tigertronics.com/slusbts.htm Rigblaster Homepage: http://www.westmountainradio.com/ Knowledge base: http://www.westmountainradio.com/knowledge_base.php Drivers and manuals: http://www.westmountainradio.com/content.php?page=wmr-downloads Page 3 of 29
Configuration Radio Interface Setup Playback settings This will adjust the audio path from the computer to the radio. Click the Start button. Click Control Panel. If Control Panel is in Category mode, first click Hardware and Sound. Click Sound. If the radio interface device (USB Audio CODEC for SignaLink) has a green check next to it, this indicates it is the default audio device. DO NOT use the radio interface as the default Windows audio device. Any sounds generated by the computer will be transmitted including system sounds, music, and screensaver noises. The radio interface will be selected in the settings of the digital application. When traveling once, some station had the radio interface set as the default audio device. The aquarium screensaver was not only transmitting bubbles but tying up a local repeater. Don t be that guy. Set the sound card as the default audio device. Page 4 of 29
Click the main sound card device. Click Set Default. Notes: Clicking Set Default will set the selected device as the Default (sound) Device and Default Communication Device. Clicking the down arrow will display the options set as default. Page 5 of 29
Click the radio interface device. Click Properties. Page 6 of 29
Click the Levels tab. Set the Speakers level to 50. Notes: Setting the audio level half-way will prevent distortion and clipping of the audio signal. Further audio level adjustments should be made using the level controls on the interface device. Page 7 of 29
Click the Enhancements tab. Check Disable all enhancements. Notes: Disabling enhancements eliminates a possible source of distortion in the audio signal. Distortions will result in undesired or no decoding of the data. Page 8 of 29
Click the Advanced tab. Under Default Format, select 16 bit, 48000 Hz. Click OK. Notes: 41000 Hz is fine for many applications. Some digital modulation requires more bandwidth. Page 9 of 29
Recording settings This will adjust the audio path from the radio to the computer. If not in the Sound control panel, click the Start button. Click Control Panel. If Control Panel is in Category mode, first click Hardware and Sound. Click Sound. Click the Recording tab. If the radio interface device (USB Audio CODEC for SignaLink) has a green check next to it, this indicates it is the default audio device. DO NOT use the radio interface as the default Windows audio device. The radio interface will be selected in the settings of the digital application. Set the sound card as the default audio device. Page 10 of 29
Click the main sound card device. Click Set Default. Notes: Clicking Set Default will set the selected device as the Default (sound) Device and Default Communication Device. Clicking the down arrow will display the options set as default. Page 11 of 29
Click the radio interface device. Click Properties. Page 12 of 29
Click the Levels tab. Set the Microphone level to 50. Notes: Setting the audio level half-way will prevent distortion and clipping of the audio signal. Further audio level adjustments should be made using the level controls on the interface device. Page 13 of 29
Click the Advanced tab. Under Default Format, select 1 channel, 16 bit, 48000 Hz. Click OK. Notes: 41000 Hz is fine for many applications. Some digital modulation requires more bandwidth. Page 14 of 29
Testing and troubleshooting This section will cover methods, techniques, and tips for testing your audio setup and ability to send and receive using your digital program. Not covered will be usage of a specific program. For usage information please go back to the website and download the instructions for that specific program. Transmit Tune the interface connected radio to an unused or simplex frequency. Use a dummy load or reduce power to the lowest setting. Setting the Time-Out-Timer in the radio to 10 minutes serves a couple purposes: it is the maximum length of time one can send a simplex transmission and not properly identify. If the radio times-out, it is immediately known a proper ID must be sent and the transmission length is way too long for a Ham Radio transmission. However, a 3 minute time-out-timer is more reasonable on an FM repeater and good for initial practice to get a sense of transmission lengths. Turn off all audio adjustments like EQ and compression. One thing that trips up beginners the most: when you are transmitting digital, in most cases, you will not hear any tones or audio. This is normal. You have to rely on your radio to indicate it is transmitting and an external source (HT, another station) to verify audio levels and/or reception. For a repeater net, tune the handheld to the input frequency of the repeater which is the frequency your computer connected radio will be transmitting. Base station radios usually have an audio indicator of some kind but it may only function in certain modes. You will need to understand your radio to know how it functions. To begin, tune an HT and the computer connected radio to the same frequency. Open the Sound Control Panel to the playback settings. Open the application and verify the settings are correct for the radio interface. Create a test transmission. Press the transmit button in the application. Page 15 of 29
When the application is sending a transmission: The application will generate audio output and raise the level meter next to the radio interface device to about half (shown above). The radio should be transmitting. Digital audio should be heard on the handheld radio. The audio should sound clean and not distorted. You re ready to transmit! If no audio is heard or the radio is not transmitting: Check for a PTT or TX indicator light on the radio interface. Does it light when sending the transmission? Adjust the TX level on the radio interface. Check the program audio input/output settings. Does the interface have a serial line (COM port) to key the radio? Check that setting in the program being tested. Most interfaces have a Monitor port that will play the transmitted audio into an external speaker or headphones. This can narrow down troubleshooting between the computer and interface or interface and radio. Page 16 of 29
Receive Testing receive is a little harder to do. You will need another amateur station, preferably one with a known working setup that can transmit the same mode and frequency. Then test two-way digital communications. Alternatively, having another local computer, radio interface, and radio will work too. Note: If you plan to leave your station in monitor mode, that is leave the radio on and application running (decoding satellite passes for example), remember to disable Auto Power Off features in the radio and sleep/power saving features of the computer. Tune the interface connected radio to an unused or simplex frequency. Have the other station do the same. Turn off all radio audio adjustments like EQ, filters, and noise blankers. Open the Sound Control Panel to the recording settings. Depending on configuration, the radio likely feeds open squelch audio to the radio interface. This is depicted above with a peaking level meter next to the interface device. Peaking here is not as important because open squelch audio is much louder than a modulated signal. Open the application and verify the settings are correct for the radio interface. Many applications open in receive mode by default. Page 17 of 29
Have the other station send a test transmission. Radio Interface Setup When receiving a transmission: Receiving a signal should produce an overall audio level of about half (shown above). The application will have some indication of receiving/decoding in progress. This depends on the program. If the message was successfully received, you re ready to receive! If the message was not successfully received: Adjust the RX level on the interface. Check the program audio input/output settings. Most interfaces have a Speaker port that will play the transmitted audio into an external speaker or headphones. This can narrow down troubleshooting between the computer and interface or interface and radio. Unlike the TX indicator light, there is no RX indicator on the radio interface. Does the application have a squelch adjustment? Page 18 of 29
Recording with Audacity Some week you can t make the net, but you still want to receive the messages passed on the net or there is an event taking place and you want to record the transmissions. There are a couple options. Leave the digital application running on your computer in receive mode. Transmissions made will be picked up and decoded by the program for later review. Disadvantages: if the net decides to change programs and/or modes, particularly ones that don t transmit an ID and require manual intervention won t be recorded. Leaving more than one monitoring program running doesn t always work because one application can take exclusive control over the recording device, bumping out the other program. Conversations taking place on the net explaining modes or information about the content would not be recorded. A second option is to record the net using a sound recording program and play it back into the appropriate digital program at a later time. This is also known as Time shifting. This method works great for monitoring the net. Do not start the digital program in addition to the recording program. Disable Auto Power Off features in the radio and sleep/power saving features of the computer. Re-enable when done. Download Audacity (free, all platforms): http://audacity.sourceforge.net/download/ You will need the administrator password to install if you are running as a standard user. Install with the default options. Start Audacity. Click OK. Page 19 of 29
Check Don t show this again at start up. Click OK. Page 20 of 29
Recording settings Radio Interface Setup For Recording Device, select the radio interface device. For Recording Channels, select 1 (Mono) Recording. For Recording Volume, select 0.50. A tooltip will appear while clicking and dragging indicating volume Page 21 of 29
level. Click Record. Radio Interface Setup When completed, click Stop. Notes: These files can be very large at approximately 610MB/hr even in temporary storage. Record all received and transmitted audio To record the received audio in addition to your transmitted audio, a separate audio cable will need to be used. Install the cable into the speaker out on the radio into the line in on the computer. The radio will need to have a monitor feature which mixes received audio with your transmissions. Set line in of the main sound card as the Recording Device in Audacity. Page 22 of 29
Timer recording Begin a recording at a specified time. Radio Interface Setup Setup Audacity as instructed in the Recording settings section. Click Transport. Click Timer Record. Set the Start Date and Time. Set the End Date and Time or the end time will be calculated based on Duration. Click OK. The timer will start counting down. Page 23 of 29
Audacity will begin recording at the specified time. Page 24 of 29
Saving Radio Interface Setup When the recording is complete, it can be played immediately or saved by clicking File. Click Save Project. Click OK on the warning message. Give the project a name. Click Save. Notes: Recording files can be very large at approximately 610MB/hr. Page 25 of 29
Playback Radio Interface Setup Go into the Recording Sound Control Panel. There should be a Stereo Mix, Mono Mix, or Wave option from your main sound card. This depends on the sound driver. If nothing similar is seen, right-click in the recording box and click Show Disabled Devices. Then right-click the appropriate device and click Enable. In the digital application, select the mix device for the input. Remember to change it back to the radio interface device when done. Notes: The mix device is not required to be the default device. Page 26 of 29
In Audacity, open the project if it is not already. For Playback Device, select the speakers of the main sound card. For Playback Volume, select 0.50. A tooltip will appear while clicking and dragging indicating volume level. Click Play. Notes: Page 27 of 29
Selecting Speakers will allow the recording to be outputted to the speakers. In addition, this feeds audio back into the mix recording device where it is picked up and decoded by the digital program as it is being played back. Decoding issues: disable all audio processing including Enhancements in the Sound Control Panel. Default Format on the Advanced tab should be 48000 Hz (1 channel for the radio interface, the rest don t matter). Verify these for all sound devices used in this setup. Usually the volume of your playback (speaker) device affects the input level of the mix device. Adjusting the level on the recording tab for the mix device may help if the speaker output level needs to be low. Page 28 of 29
Sound card clock calibration This concept goes above and beyond the Digital Net but is important when operating some digital modes. All sound cards are not 100% accurate in their sampling rates. In normal audio sound applications, this tends not to matter. Digital modes like MFSK, SSTV, and Olivia require an accurate sound card clock. Other modes are more forgiving like MT63 and PSK. A difference can be calculated between the stated sample rate and actual sample rate of the card. Experiencing one or more un-calibrated sound cards results in decoding errors or little to no decoding of a strong signal. Some programs can auto correct on receive. The results are often best guess and not always correct. Auto Slant in MMSSTV is an example. Those who commonly operate those modes will want transmitting stations to calibrate their sound card. Each program has its own method for doing this. Here are common examples: SSTV: http://www.wb9kmw.com/wb9kmw/sstv_files/tutorial/that_pesky_slant.pdf. I prefer this method: http://www.wb9kmw.com/wb9kmw/sstv_files/tutorial/that_pesky_slant_wwv_alternative.pdf. Fldigi: http://www.k8jtk.org/2015/10/19/nbemsfldigi-sound-card-calibration/ Page 29 of 29