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Connecting Radios to Soundcards


Welcome to the Connecting Radios to Soundcards article. Soundcard software has come a long way in the last few years, and has the ability now to manipulate and use audio inputs in a variety of ways. For us scannists, 2 reasons invariably pop up;

  • I want to decode (or record) a signal I heard on my scanner - or -
  • I want to decode (or record) a signal I heard on my HF radio

This article discusses the basics of setting up Windows to accept audio from your radio. At the bottom, there are links to articles with numerous software packages, some of which can be used with a soundcard input.

Before we proceed, it should be noted that settings may appear different in different OSs, and with different PC distributors, who often put their own soundcard support software in their systems. The images -and text - in this article should be used as a guide, not as specific examples. In addition, connecting a soundcard to a ham transceiver is a much more critical function, as isolation between the transceiver and PC is a must. For extensive discussions on the subject, please see the Understanding Soundcard Interfacing website.

Contents

Soundcard Setup

Figure 1
Figure 2
Figure 3

1. Double click on the Speaker Icon in the System Tray. If you don't see a speaker Icon, go to Start/Control Panel/Sounds and Audio Devices. Then select the Volume tab, then Advanced under Device Volume

2. The Properties panel (Figure 1) should open. You should have two options; Playback and Recording. Select the Recording radio button. Select the input(s) you wish to use. In general, you will want Line In and/or Mic In, dependent on what is available on your machine. Hit OK

3. In the Recording Control panel (Figure 2) make sure that the desired input is NOT muted (some software - such as the one shown at the right - requires you to select the input).

4. This is where things can get a little hairy. In the Master Volume panel (Figure 3) make sure your desired input is NOT muted.

  • If you have a microphone you can use it to decode digital modes, etc. Just plug it in, and set next to your radio. Depending on the type of microphone you have you may or may not need to set the Boost Gain, somtimes called +20db; this can be found in Advanced Controls. Generally this is the least desired option as the microphone can pick up ambient noise in the room which can ruin your recording. Use of the Mic In or Line In is far better; Depending on your radio, and which output you use, you may need to set the Boost Gain.
  • Tune some constant audio source; something that is always busy. A NOAA weather station is a good choice. Adjust the levels to about halfway to start.

5. Another setting to be sure to check is if your soundcard is in Full Duplex, sometimes called Full Hardware Acceleration. This can be found in the audio selection in Control Panel as described above. All soundcards are different; you may need to check for Full Duplex Recording as well. This sets the sampling rate i.e. 44100hz, 48000hz or 96000hz. Some sound cards have other rates; the higher the rate the better the performance, the lower the rate the more stable(for slower computers).

Vista Users

While these instructions are for the microphone input, the line input (if your PC has one) should be able to be set up in the same manner (thanx to UPMan for the procedure);

  1. Right click on the Speaker icon in the system tray, and select "Recording Devices."
  2. Double click on the Microphone.
  3. On the Microphone Properties General tab, make sure the bottom box says "Use this device (enabled).
  4. On the Levels tab, increase the level to 50.

Other Considerations

  • The Bit Rate is important; 8 and 16bit are the most common; high bitrates allow for smoother audio response and better throughput.
  • You can use Stereo and Mono Mix Recording settings to record real time audio from your computer, Internet, Chat Rooms, Programs, etc. It can also be used to record audio from a SDR (software definded radio); if it does not support recording from an audio source, it may be fed through the USB Jack.
  • If you have onboard sound built into your mother board and find it's not working, or has very poor quality, you can pick up a cheap $30 Sound Blaster Sound Card from WalMart which supports 96000hz, and 24bit Sound

Cabling and Hookups

  • The use of shielded audio cable is strongly recommended. Make it as short as possible to minimize stray pickup.
  • Many soundcards require a stereo jack (1/8 inch) as input. Simply wire one side (either right or left). It may also be possible to short the 2 sides together. Check any available documentation on your soundcard for specifics.
  • Laptops may require an attenuating patch cord, since their inputs may be designed to handle low-level inputs. If you hear distortion no matter what audio level you set, this is likely to be a cause. An example of an attenuating patch cord can be found here
  • A resistor across the jack is an easy way to assemble an attenuating patch cord. One way to find the correct value would be to connect a 10k audio taper potentiometer across the jack, along with a Volt Ohm Meter (VOM). Begin with maximum resistance, and slowly decrease it until the audio sounds normal. You may need to also adjust the levels in the soundcard's control panel. When the audio is satisfactory, note the reading on the VOM. You now have an idea of the resistor's value.

Problems and Solutions

  • Most stand alone recording programs like RecAll or ScanCorder, will tag the audio file with date/time and duration.
  • Older Radio Shack scanners- with the exception of the PRO-2052 (which is really a Uniden clone) cannot log frequency or talkgroup information. It's not provided for in the firmware. However, the PRO-197 and PRO-106 (which are RS clones of the GRE PSR-500 and 600) can do this with the proper software.
  • No audio is heard through the PC speakers using either 'Line In' or 'Mic In' jacks on the soundcard
    • Make sure that neither of these selections has been muted in the control panel for the soundcard (see above)
  • An A/C type hum is heard, even when receiving nothing.
    • Double click on your speaker icon on your taskbar, go to Options, Properties, change "Adjust volume" to Recording, hit OK, and under Mic, there should be an advanced, and see if 20 db boost is enabled. (Evan Platt via Scan-L)
    • Many Uniden receivers put a resistor in the headphone jack circuit to limit the output. This is in the ground side of the jack and can cause hum if you are trying to use it for a tape input. According to the manual, the 796D has a programable tape output on the rear panel. See page 18 of the manual. If you still have hum, get a ground loop isolator such as these from Best Buy and the necessary adapters.
  • The BC796D (and possibly the BC785D) has a tape output jack; however, it seems to activate after a 2 second delay. To get around this, connect to the speaker out jack instead

Soundcard-Driven Software

Regardless of the application you are trying to execute, if you have Windows Vista You may need to check to see if your software is compatible with it. XP support is far more widespread, with less problems; however it too has a compatiblity feature that allows you to tell XP if your particular program need to run as if it were in Win95, 98, etc. or in other modes/colors.

  • If you need to restore soundcard settings, or have a way to set different settings for different applications, then you should look into QuickMix.

Thanks to Shortwavewave for the pix and some of the text


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