Welcome to the new FlexRadio Community! Please review the new Community Rules and other important new Community information on the Message Board.
If you are having a problem, please refer to the product documentation or check the Help Center for known solutions.
Need technical support from FlexRadio? It's as simple as Creating a HelpDesk ticket.

Voice Operated Squelch

Simon Member
Why not enhance the SmartSDR for 6000 series with VOS.
It cannot be too hard with SDR to add algoritms to mimic a circuit which responds to normal human speech while ignoring other forms of audio. The voice operated squelch exists as a circuit in many commercial HF stations like Motorola's "Constant SINAD" squelch that is used in the Motorola Micom HF SSB Transceivers.
Request For New Feature
0 votes

In Review · Last Updated

This is currently an outstanding feature request


  • Norm - W7CK
    Norm - W7CK Member ✭✭

    I asked for this YEARS ago and was told by the owner of Flex that the Flex doesn't need squelch. If you look back through the old posts, you will see I even got chastised for even bringing it up. "Contesters don't use it and therefor its not needed". At the end of a rather sad dialog, It sounded like it was never going to happen. There were lots of very strong opinions in favor of not adding squelch. This makes using all 8 receivers on the 6700 a bit more difficult and not as enjoyable as it could be. There are 3rd party apps that let give you some sort of squelch but not as good as it could be if incorporated right into SmarSDR.

    SmartSDR has been with us for many years now and still lacks functionality in areas that some would consider basics. There are also some fairly important bug fixes that have been on the books forever and have never been addressed....

  • JCP
    JCP Member
    [{"insert":"Back in the 1980's, I worked for Communication Associates Inc. in Huntington Station, NY.\nThey had an excellent SSB Voice Squelch that would detect the human voice, no matter how far down in the mud the signal was.\nBasically it consisted of:\n1) An audio discriminator across the audio band (say 300 Hz to 3 kHz) (generation a DC voltage proportional to frequency).\n2) A 10 Hz low pass filter on the discriminator output (10 Hz is the human voice symbolic rate).\n3) A rectifier after the low pass filter.\n4) And finally a threshold detector on the rectifier output.\nSomething that could easily be added to any modern radio with a little excess signal processing capability.\nJohn WB2CIK\n"}]
  • Lyman duggan
    Lyman duggan Member, Unconfirmed
  • WX7Y
    WX7Y Member ✭✭✭✭

    This is kind of accomplished today using Software, Specifically FreeDV https://freedv.org/ .

    SmartSDR used to have a API that lost support and thus removed from SmartSDR because the API author didn't have time to keep up with how fast the FreeDV program was advancing and it wasn't hard to interface the FreeDV Program to the Radio DAX and CAT all you need is an additional MIC like a USB headset. There is Software for the Windows, and MAC OS and updates done quite often.

    There has been slow but gradually more Activity with people using this Digital Voice Mode and there are several nets.

    This lets you use less bandwidth and "8 kHz wide audio bandwidth, while using just 1600 Hz of RF bandwidth"

    With the FLEX's High Dynamic range it works very well especially if you don't overdrive it, you can use much less Power to accomplish the same communications as SSB kind of like FT8 does.

    Just a thought

  • Trucker
    Trucker Member ✭✭✭

    FreeDV might work as a Squelch for that mode. But, it isn't that widely used, so it won't help 99% of users on HF.

    A Syllabic Squelch like that created by Motorola years ago would be great. I think Warren Pratt created an open source version some time ago that is included in his WDSP library. If it's anywhere near as good as his Noise Reduction 2 code, it would be great to have in SmartSDR. ( as well as his Automatic Notch Filter )

    But, I have my doubts that any improvements in that area will happen for SmartSDR.

    Merry Christmas!



Leave a Comment

Rich Text Editor. To edit a paragraph's style, hit tab to get to the paragraph menu. From there you will be able to pick one style. Nothing defaults to paragraph. An inline formatting menu will show up when you select text. Hit tab to get into that menu. Some elements, such as rich link embeds, images, loading indicators, and error messages may get inserted into the editor. You may navigate to these using the arrow keys inside of the editor and delete them with the delete or backspace key.