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Technical Topics => SDR - Software Defined Radio => Topic started by: Ray Lalleu on October 23, 2019, 0911 UTC

Title: Automatic clarifying of SSB signal with SDR ?
Post by: Ray Lalleu on October 23, 2019, 0911 UTC

I'm wondering if any SDR software is able to automatically fine tune a SSB signal to perfect clarifying, though no carrier or pilot tone is transmitted,
with this trick :
finding the strongest tones in the passband,
then looking to find the harmonically related ones,
then computing the exact missing carrier frequency,
and using it for the best SSB decode.

Of course, the tone content of an audio signal is heavily variable, but within a few milliseconds, sustained notes in music should be enough for all that computing work, and  once in sync, the demodulation should stay in sync just like a good AM sync demodulator when the carrier goes down by selective fading.

Title: Re: Automatic clarifying of SSB signal with SDR ?
Post by: Josh on October 23, 2019, 2235 UTC

I imagine the stuff made by comintconsulting, R&S, and the rest of the spookware makers have the ability to tune ssb voice sigs automagically, or at least they better considering how much they charge.

Title: Re: Automatic clarifying of SSB signal with SDR ?
Post by: Pigmeat on October 26, 2019, 1609 UTC

They need clarifier or BFO knobs for the consumer models. Trying to reinvent the knob is getting them nowhere fast. Hiring a CalTech genius with extensive knowledge of advanced knob technology could solve their problems overnight, but they don't come cheap. Some of them insist on being fed.

Title: Re: Automatic clarifying of SSB signal with SDR ?
Post by: KaySeeks on November 21, 2019, 2146 UTC

Quote from: Ray Lalleu on October 23, 2019, 0911 UTC

finding the strongest tones in the passband,
then looking to find the harmonically related ones,
then computing the exact missing carrier frequency,

I think that there are many potential pitfalls with this:

• Is the modulation composed of voice or music or both?
• If the fundamental tone is greater than ~1.5 KHz, the second harmonic might be severely attenuated.
• Depending upon the audio circuitry, the odd harmonics (3rd, 5th) might be stronger than the even ones (2nd, 4th). How do you know which is which?
• As you noted, selective fading could throw a spanner in the works.

Title: Re: Automatic clarifying of SSB signal with SDR ?
Post by: chanito on December 17, 2019, 2010 UTC

https://patents.google.com/patent/US7826561B2/en

Title: Re: Automatic clarifying of SSB signal with SDR ?
Post by: Josh on December 17, 2019, 2130 UTC

Interesting the patent's assigned to Icom.

Title: Re: Automatic clarifying of SSB signal with SDR ?
Post by: chanito on December 17, 2019, 2152 UTC

There's other pertinent info there including mentions of other attempts as this technology. There's at least one post I found out there from a guy who claims to have a working software based system that auto tunes SSB.