THE PROBLEM:
How many times have you wished to have a small, versatile, intuitive, easy to operate, precise, informative, useful, fast, low cost, audio and low frequency, spectrum analyser module for all-round projects? I always dreamed about that. I tried many types of spectrum analysers for measuring low frequencies, but all of them were not informative, and very slow at low range. You can buy built-in LCD DVM, Oscilloscope, Counter modules, but not a useful spectrum analyser module.

SOLUTION:
This construction is based on a PIC 32MX460F512L microcontroller. I used a Mikorelektronika Mikromedia development board, and made two additional boards, control and analog filter board.
The PIC was programmed in C program language. DFT was applied for spectrum analyses. Analog and digital ground are carefuly separated.

Problems to solve:
- Internal spectral noise from PIC board
- Phantom peaks produced by higher frequencies than Spectrum range
- Phantom peaks generated from IC's from board
- Fast analyses in the range from 1Hz to 80Hz
- The frequency precision in the first place, than amplitude
- To make intuitive and informative front panel

Characteristics:
- Spectrum analyser built in, or stands alone 3.6 x 3.1 inch panel meter
- Fast, C program language code,
- 80Hz, 700Hz, 7KHz, 19KHz and 35KHz range, 320x240 TFT bright, clear display
- Calibrated in dBu (most suitable for audio, can be calibrated in any scale)
- Find the highest three peaks, show frequencies
- Show input in Vpp
- Overload warning
- Peak Hold
- Powered by USB or LiIon battery (charged via USB), or use external DC
- Max input 4Vpp, input noise max 0.2Vpp
- Compact and slim, fit in the palm of the hand, suitable for all mobile equipment
- Module also can be used programmed, without control logic and analog board
- Nice Tek-look design

Designed for:
- All audio and voice testing and measuremets, testing amplifiers, filters, networks, speakers...
- Vibration, measurement
- Power sources quality analysis
- Measurement of electromagnetic low frequency fields
- Spectral analysis of biomedical signals, ECG, EEG, EMG

GOALS:
- Make market wide applicable small and low cost module for amateurs and professionals,
Making spectrum analysis accessible for all
- Low cost production and service
- To sell a know - how

THE COMPETITIVE ADVANTAGE:
-The smallest audio and low frequencies spectrum analyser built-in or stand alone module
- Fast at 80Hz range
- USB or LiIon battery powered
- Low cost, 150$, fair characteristics for that price
- Suitable for Your projects

I was inspired by vintage Tektronix scopes. This is my modest contribution to remember the spirit of that time.
Jim Williams sums that spirit when he speaks of the Tek 535 era:
"The 535's engineering concepts and production execution were a bumpless combination of interdisciplinary technology, inspired design, attention to detail, aesthetics, and usability. It combined solid knowledge of fundamentals, unbounded thinking, and methodical discipline to produce a superior result. The thing just radiated intellectual honesty."