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Re: [linrad] RE: Silly question or is it?

HI, Leif and all!

Thanks for the excellent discussion on the central discontinuity. I will save it and read it several times as there is a lot of information there ;)

As for the question:

Changing Just Second Forward FFT routine from [2] to [1] to [0]:

[2] gives 17.2 second total delay, 10.92 sec FFT2 delay, 59.4% CPU load

[1] gives 6.89 second total delay, 2.73 sec FFT2 delay, 61.5% CPU load

[0] gives 6.90 second total delay, 2.73 sec FFT2 delay, 63.9% CPU load

the delay with [2] really surprised me! (though I know there is a simple reason it shoudn't have done so).

Are you sure that nothing was changed in the AFC or baseband parameters?
There should be nearly no difference at all in total delay depending
on the different fft versions.

If the total delay really is different (by more than 0.1 second) on
your fast computer, please give me detailed information because then
you have (again) detected a bug;)

Yes, I just did it again. With [1] as the choice for 2nd forward FFT routine my total delay is: 6.96 seconds and the fft2 delay is 2.73 sseconds.

I go into the parameter screen and change it to [2]. I change nothing else and directly leave the parameter screens by repeatedly hitting enter and keeping my mouse out of trouble. Now my total delay is 17.22 sec and the fft2 delay is 10.92 seconds.

I go back to [1] as the choice and the delay is again 6.97 seconds and the fft delay is 2.73 seconds.

Here are my parameters:

First FFT bandwidth (Hz) [50]
First FFT window (power of sin) [3]
First forward FFT version [5]
First FFT storage time (s) [20]
First FFT amplitude [300]
Enable second FFT [1]
First backward FFT version [0]
First backward FFT att. N [8]
Second FFT bandwidth factor in powers of 2 [6]
Second FFT window (power of sin) [2]
Second forward FFT version [1]
Second forward FFT att. N [8]
Second FFT storage time (s) [30]
AFC lock range Hz [150]
AFC max drift Hz/minute [100]
Enable morse decoding [0]
Max no of spurs to cancel [100]
Spur timeconstant (0.1sek) [5]
First mixer bandwidth reduction in powers of 2 [4]
First mixer no of channels [1]
Baseband storage time (s) [200]
Output delay margin (0.1sek) [5]
Output sampling speed (Hz) [6000]
Default output mode [55]
Audio expander exponent [3]
A/D speed [96000]
Check [1110038]

I found this interesting behaviour. The difference in total delays in on the order of 10.26 seconds.

Let me know what else I can do here. It would be interesting to see if anyone else sees this behaviour with these parameters.



Roger Rehr
2 Merrymount Road
Reading, PA 19609