Re: Why when I send a complex file with harmonic sequence f1 f2 f3 ...fn, In receiver haromoic sequence gain is changed?

[Marcus Müller]

Hi!

What you describe is a "frequency-selective channel", not harmonic distortion; frequency 
selectivity (or: channels that are not *flat*) are pretty common in communications.

Harmonic distortion is when your tones intermodulate (with each other or with itself), and 
an effect of nonlinearities. In which case, 99% of the time people configure their gains 
far too high, run into saturation or even clipping. But you'd see that in the distribution 
of your receive amplitudes (try the Qt histogram sink!).

Best regards,
Marcus

On 08.05.22 08:06, sp h wrote:
> Why when I send a complex file (With USRP x300) with harmonic sequence f1 f2 f3 ...fn, In 
> receiver (USRP x310) harmonic sequence gain is changed?
> For example, I have a complex file the FFT of a signal has some harmonic peaks 
> f1 f2 ...fn
> gain of harmonic peaks in the original file is:
> f1:2
> f2:2
> f3:3
> f4:4
> ...
> fn=3
>
> But receiver loss or amplify harmonic peaks are not consonant
> For example, in the receiver we had:
> f1:5
> f2:1
> f3:4
> f4:7
> ...
> fn=.1
>
> So when I used MatLab to convert complex files to Wav and play file original file and 
> received file is not exactly the same...
> some higher frequency is suppressed or the sound is more bass. Is this subject 
> related to TDH?
> In USRP what's TDH?
> https://en.wikipedia.org/wiki/Total_harmonic_distortion 
> <https://en.wikipedia.org/wiki/Total_harmonic_distortion>
> can anyone guide me?
> Thanks in advance

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