Spectrum Lab provides Spectrum Analyzer with Waterfall Display and real-time audio processing. started as a simple FFT program running under DOS a long time ago, but it is now a specialized audio analyzer, filter, frequency converter, hum filter, data logger etc (see history at the bottom of this page). You can download it from this site. Or look into the manual though the manual included in the archive will be more up-to-date.

Why "is Spectrum Lab"?
1. Analysis of audio signals to the PC and the sound card (Or an external A / D converter)
2. Analysis of the spectrum in a sound file (WAV)
3. Tracking the time course of a spectrum as "Waterfall" display (spectrogram), mono or stereo "
4. Range finders to DF6NM (with suitable receiver)
5. Measure and record noise level, peak values of Amplitude + frequency, ... in the form of text files for propagation studies on long-and short-wave
6. Digital signal processing in real time, u.A: Filtering, frequency shifting, Modulation / Demodulation
7. Generate and decoding of some specific types of modulation have been used by radio amateurs / are (experimental!)
8. One-or two-channel measurement of amplitude and phase running (in the help text "Time domain scope" called)

Spectrum Lab Features:
1. Input can be taken from the soundcard, but the "audio utility" interface makes it possible to create an interface to any A/D converter you like (for example a PIC with serial interface). A plugin for Winamp allows to analyse audio streams from the internet (see download section).
2. Besides the soundcard and the interfaces supported by the "audio utilities", SpecLab directly supports SDR-IQ and SDR-14 (by RFSpace, Inc), and PERSEUS (by Microtelecom s.r.l.).
3. Demodulated output is usually sent to the soundcard, but can be sent anywhere else (including an MP3- or OggVorbis encoded stream using Winamp/Oddcast and a special Audio-I/O DLL, which acts as an input plugin for Winamp).
4. Selectable and adjustable waterfall color palette allows you to change the contrast of the waterfall display during and after receiving spectrum lines ("contrast" & "brightness" - sliders)
5. Frequency range can be adjusted while running, the old part of the waterfall display will automatically be re-drawn without stopping the audio processing.
6. Special waterfall mode for "Radio Direction Finder" with colour-coded azimuth display, based on DF6NMs Wideband Direction Finder with Colour Encoded Spectrogram Display. Now with up to three "notches" (adjustable nulls in the synthesized antenna pattern) to suppress noise from certain directions.
7. Special "multi-strip" waterfall mode for long term observation of relatively narrow bands
8. Reassigned spectrogram for higher time- and frequency resolution, if certain conditions are fulfilled (since 2009-06)
9. Support for image-cancelling direct conversion receivers ( quadrature input via stereo soundcard )
10. Very sharp, FFT-based audio filters which can also be used to shift and invert frequencies, with auto notch, denoiser, etc. New (2007-02): Write your own plugin for the FFT filter !
11. Waterfall display may run from top to bottom, or from right to left (good for HELL modes)
12. Calculation of peak levels, peak frequencies, noise levels, effective values, SINAD, etc
13. File logging and file analysis with WAVE files ( now with Triggered Audio Recorder + pre-trigger option )
14. Periodic or scheduled actions, for example to capture the screen as BMP or JPEG file
15. Audio sample rates from 8000 to 192000 samples per second.
16. 192 kS/second only tested with a few cards, using ASIO drivers and / or standard multimedia driver. With extra hardware (like software-defined receivers with high-speed USB interfaces), even higher sampling rates (and thus bandwidths) are possible.
17. 16-bit ADC resolution giving about 90dB of input range (plus additional FFT gain!)
18. 24-bit resolution possible with certain cards (tested with Audigy 2 ZS; 2004-05)
19. Frequency resolution in the sub-milliHertz range (exceeding the stability of the soundcards clock generator).
20. FFT output is buffered in an array with adjustable size for long-term observations (with "scroll-back-in-time" while analysis continues). Furthermore, the FFT output can be recorded (exported) in various formats.
21. Signal generators with selectable waveform, frequency, and optional modulation, plus noise generator
22. Hum filter to remove 50 Hz (or 60 Hz) plus harmonics, based on Paul Nicholsons algorithm for a multi-stage comb filter with automatic tracking. If you are interested in improving your Natural Radio reception, read Pauls Notes on Domestic VLF Reception.
23. Frequency converter to shift low "IF"-frequencies (e.g. 17.2 kHz) to audible tones (650 Hz, etc) in real-time. Can be used in a soft-VLF-RX. Other demodulators in DSP-blackbox.
24. Decoder for some time-code transmitters: MSF(60kHz), HBG(75kHz), DCF77 (77.5kHz) can now be used to set your PC clock to a high accuracy. All you need is your longwave receiver and the soundcard.
25. Modulator and decoder for some experimental digital communication modes like PSK31, BPSK, QPSK, FSK, multi-tone HELL, MSK (minimum shift keying since 2004-12), transmission and reception of letters with a small terminal window.
26. A DLL interface is available to use Spectrum Lab for new digital transmission modes (but not in use yet).
27. Fast waterfall with up to 200 waterfall lines per second, making it possible to decode even fast Morse code by eye (though it wasnt intended for that, its fun to watch)
28. versatile export function (text-file based, for post-processing with Excel etc.). Brian, CT1DRP has used the export functions to create spectrograms and signal graphs of the 136kHz band.
29. Built-in HTTP server so you can write a (simple) user interface for SpecLab in HTML (intended to be used in a LAN, not as a fully-fledged web server).
30. Communication with other applications through a simple message-based system, which is also used by SpecLab to communicate with the RDF calculator (range-and-bearing calculator + map plotter, link may work on the main site only).

The license of this software is Freeware, you can free download and free use this audio utility software.