Hi Leif, Speaking as an old physicist I note that there is nothing in the world of physics to establish the frequency of a biological voice. I think you have reached a dead end. Perhaps someone else can demonstrate that without transmitting a known audio tone (a test tone) the BFO frequency is indeterminate.
As you suggest, known distortion elements will lead to the BFO frequency. But only if you can know which elements are the distortion. 73 Bill, NL7F On Wed, 27 Sep 2006 00:27:09 +0200, Leif Asbrink wrote: >Hi All, > >How does one know what the correct bfo frequency >is when listening to SSB? With a waterfall graph it is pretty >obvious what frequency to select to make the signal fit the >baseband filter - but that does not give any hint on how far >outside the filter one should place the BFO. > >For Linrad-02.18 I have tried various algorithms to try to >extract the correct bfo frequency, but all have failed on >real HF signals with speech processing and selective fading. > >Actually I can not set the correct frequency even when >listening to the audio. I can change the pitch of the voice - >but I do not know what would be the correct pitch. Only on >those stations (really a large fraction of all) who have a >carrier or who have intermodulation distortion to produce a >signal at the carrier frequency as well as on the other >sideband I can set the correct pitch using the information >on the baseband waterfall display. By ear I can not judge >whether I make a 50Hz error. > >I have tried cross correlation as well as fft and both give the >voice fundamental frequency with similar accuracy but I have not >found any way to extract the bfo frequency. The accuracy is simply >not good enough to decide which spectral line to associate to >which voice overtone. Not on real HF signals that have the phase >vs frequency function severely distorted by multi-path propagation. > >Is there anyone on this list who has an idea what to do? >If not, I will just skip automatic bfo setting as well as AFC >for Linrad in SSB mode. > >73 > >Leif > > >############################################################# >This message is sent to you because you are subscribed to > the mailing list <linrad@antennspecialisten.se>. >To unsubscribe, E-mail to: <[EMAIL PROTECTED]> >To switch to the DIGEST mode, E-mail to <[EMAIL PROTECTED]> >To switch to the INDEX mode, E-mail to <[EMAIL PROTECTED]> >Send administrative queries to <[EMAIL PROTECTED]> > Bill Beam NL7F <wbeam at gci dot net> or <NL7F at amsat dot org> -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.1.407 / Virus Database: 268.12.7/454 - Release Date: 9/21/2006 ############################################################# This message is sent to you because you are subscribed to the mailing list <linrad@antennspecialisten.se>. To unsubscribe, E-mail to: <[EMAIL PROTECTED]> To switch to the DIGEST mode, E-mail to <[EMAIL PROTECTED]> To switch to the INDEX mode, E-mail to <[EMAIL PROTECTED]> Send administrative queries to <[EMAIL PROTECTED]>
