LF SPECTRUM ANALYSER USING SB-16 SOUND CARD.

The fft.exe program is a simple LF (0..20Khz) spectrum analyser using
the SB-16 ( or 100% compatible like AWE32 ) as sampler.
I calibrated ( more or less) the display for my AWE32 sound
card  (0dBm = 0.7746V eff in 600 ohm). You can re-calibrate the program for
your sound card by changing the variable <system_adjustment> in the file
fft.cpp and re-compile the program.

1  MINIMAL SYSTEM REQUIREMENT
   386 + CO-processor ( 486DX2 recommended).
   VGA display ( 640 x 480 dots, 16 colours).
   DOS 6.2 ( program will not run properly in a DOS window )
   SB-16 or 100% compatible sound card

2  OPERATION
   The program is fully mouse controlled. The only functional key
   is <ESC>  to exit the program.  Most controls are strait forward,
   only three need maybe some explanation.

   A. On screen measurement.
      If the mouse cursor is in the display array, and you <left-click>,
      the display will freeze, the cursor will be limited to the display
      area and the value of the cursor position is displayed.
      If you <left-click> again a second set of values is displayed,
      relative to the actual cursor position. <Right-click> to leave
      the on screen measurement mode.

   B. MODE: scope.
      The purpose of the scope mode is to check if the input signal is
      limited either by the DAC or the input amplifiers on the sound card.
      Limiting by the DAC is clearly visible on the spectrum display,
      but limiting by the input amplifiers ( or maybe protection )
      only disturbs the signal. ( for my card, this occurs at
      signals > 1,2 V eff )

   C. INPUT: internal.
      I added a simple function generator, that produces an rectified
      sine_wave with some noise to be able to show a picture if no
      sound card is in the system.

3  BUGS /  IMPROVEMENTS
   If you find bugs, or have a bright idea how to improve this program
   you have two options
   1. Let me know, and maybe I will make an update.
   2. Make your own version,  ( source is included ) and send me  a 
      copy.
	

Henk Thomassen
thonass@IAEhv.nl


DISCLAIMER
I will not claim responsibility for any damages caused by the use or
misuse of this product. This product is distributed 'as is' with no
warranty expressed or implied. I will not be responsible for any losses
incurred, either directly or indirectly, by the use of this product.
Use this product entirely at your own risk.


