[quote=klaus;32755As your samples are real, you dont even need to add the imaginary samples with 0 values.
I entered 4096 real samples in the data() array without adding imaginary samples. You get 2048 real and 2048 imaginary samples in response from the Fft.Transform. [/QUOTE]
I tested this with another version, and you are absolutely right:
An fft transform of a 4096 byte array with all real values gives indeed the 2048 real and 2048 imaginary numbers as a result, containing all necessary information.
An fft transform of what I did first, that's a 8192 real+imag byte array, with a real sample and a zero, a real sample and a zero, and so on, gives off course the double number of results, but the last half is completely symmetric, and therefore useless to anyone. That's the way MS Excel does it, and I should have known:
Anyway, my arrays are only half as large now, probably giving even more speed improvement, and especially less memory usage. Thanks for the tip !