Written in Delphi 5. The product is another Computec initiative. It is sold internationally as a shareware product.

EchoFilter uses the soundcard of a PC to process income audio signals in real-time. The narrow filter bandwidth allow the extraction signals and sounds from the audio signal that may normally be close to inaudible. The real-time spectrum analyzer and spectrogram gives the user an excellent visualization of the audio. The program also includes an automatic gain control, frequency shifting, graphic equalizer, audio compressor and expander, wave file player and recorder and noise reduction filters.

It is intended for radio HAMS, hobbyists, researchers, scientists and students in the DSP field. Uses include weak signal detection, surveillance, audio cleanup, SETI operations, etc.

Other features include:

1. Adjustable maximum audible frequency range up to 16 kHz (32 KHz sampling rate)
2. Ultra sharp digital filter down to 20 Hz. High pass, low pass, band pass and stop band filters. Non-technical and extremely easy to use.
3. Spectrum analyzer with adjustable resolution and virtual scrollable display. Maximum resolution is 7 Hz.
4. Dominant frequency readout for a 7 Hz resolution frequency counter.
5. Spectrogram with same resolution as the spectrum analyzer. Configurable color palette with continuous color gradient for a very smooth display. The Spectrogram can be scrolled vertically to 2200 pixels. Horizontal length is determined only by available memory and can vary from 3 minutes to 25 minutes (there are 8 lines in a second).
6. Adjustable spectrum and spectrogram windows. Slide one of them away to turn EchoFilter into a spectrum analyzer or spectrogram only application.
7. Time averaging (smoothing) of spectrum for the detection of weak signals.
8. Adjustable automatic gain control of input signal.
9. Real-time frequency shifting (spectral shifting). Make very low and high frequencies hear-able.
10. Real-time audio compressor and expander with adjustable threshold and gain.
11. Graphic equalizer. Also functions as a series of adjustable band filters.
12. Wave file recorder and player.
13. Noise reduction filters.
14. Single file 32-bit application.

EchoFilter Examples

The spectrogram settings tab

A spectrogram of the 14 MHz radio amateur band

The spectrogram of a WEFAX signal

The EchoFilter main screen