Vox Actuated Recorder

for Windows
1996-98 Nino Porcino, ninopo@tin.it

INTRODUCTION

Vox Recorder is a Windows utility wich allows recording sound from an audio source only when an audio signal is present; its main purpose is to avoid the recording of the silence eventually present at the input.

Vox Recorder has been designed in particular for radio-scanner hobbists. If you are one of them, you already know how much time has to be spent when monitoring a new frequency: the traffic on the new channel is very sparse and communications are short, with long pauses between each one.

With Vox Recorder you can compress a whole day's worth of monitoring onto a single .wav file.

You can leave the computer on and connected to a scanner at home while you are at the office or doing something else; later, you can listen the messages caught by your radio how many times you want. In this way you can quickly monitor suspicious channels and have all the "action" into a single audio file. Permanently monitoring your neighbours cordless phone is now possible! Let your computer listen for you!

LICENSE

Vox Recorder is a free software. You can copy it and share it as long as you don't charge any money and you don't modify it. Any commercial distribution without the written permission of the author is strictly prohibited.

If you use the program please send me some feedbacks so I can be encouraged for future releases of the program. Contact me at:

email: ninopo@tin.it
web:
http://ninopo.freeweb.org

or via snail mail:

Nino Porcino
Via dei tulipani 21
89133 Reggio Calabria
ITALY - EUROPE

I would thank Mr. Pedro Delgado pcl36587@alfa.ist.utl.pt for his precious job on the english doc and for for the first test of the program.

HARDWARE REQUIREMENTS

You need:

INSTALLATION

Simply create a folder and unzip therein the program files. Eventually create a shortcut icon for a quick launch of the program. Vox Recorder doesn't touch neither the Windows registry nor the system folder, so to uninstall it simply delete its folder.

RECORDING WITH VOX RECORDER

  1. Connect the scanner's output (headphones or other plug) to the computer's sound card input with the shielded audio cable. For better results, use the "line-in" plug instead of "mic-in" on the computer side.
  2. Make some volume recording tests with the Windows sound recoder by tuning the radio on a crowded channel. Make sure the audio isn't too low or too high (distorted).
  3. Tune the receiver to the desidered frequency and choose the right squelch threshold.
  4. Run the program by clicking on its icon and enter a destination file name (vox.wav on the desktop folder by default).
  5. Click on the Record button to start monitoring and Stop when finished.

You may also want to adjust the Threshold and Decay sliders. Threshold is the minum signal at wich the recorder is activated. Place it a bit above the backgound noise of your channel. Decay is how much time the recorder waits before triggering itself off when silence is recognized. Low values make the communications very fragmented, high values make each communication last more.

For long periods of monitoring turn off the computer monitor: you'll save energy and you'll reduce interferences caused by your computer (expecially if you have an indoor antenna).

PLAYING THE RECORDED FILE

Currently the program does not have a built in player (it had one when was for MS-DOS platform). You can use Windows media player or similar tools to list or edit the .wav file you've recorded. You can simply double click on the file icon to launch the default Windows player "sndrec32.exe" (altought I've noticed it tends to make a big harddisk swapping if the file is large enough -- just use the mediaplayer instead).

Audio files produced by Vox Recorder are common 8-bit PCM .wavs sampled at a 22050 Hz rate. This means that you need 22050 bytes (22K) to store a single second of recording. Usually this isn't a problem. Monitoring radio channels with occasional traffic will result in a few minutes of recording per day. I suggest to run Vox Recorder with at least 60 MB of free disk space.

HISTORY