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What Is Meant By Binaural Reception In The FLEX Radios ?

Paul, WB5AGF
Paul, WB5AGF Member
edited June 2020 in SmartSDR for Windows
(If this duplicates some earlier inquiry I apologize but a search did not seem to find that this question had previously been asked.)

I've been wanting to ask  .... What is the term 'binaural' being used to mean as it applies to the receive audio options in the FLEX radios ?

The reason I ask ..... If you go back several decades in 'QST' and 'Ham Radio' magazines the term binaural was used to indicate a high-pass/low-pass audio filtering scheme in which higher and lower audio frequencies were selectively fed to the left & right earphones of a stereo enabled headset.

A simple implementation of this would be to have two parallel paths of active RC audio filtering with one being a low-pass filter and the other being a high-pass filter. The -3 dB frequencies of the two filters would be set equal at some frequency roughly in the middle of the audio range where most people like to listen to CW tones (say 700 Hz) and, with the same monaural audio signal from a receiver being fed to the two filter paths, the resulting audio streams would then be fed to the left and right earphones of a stereo headset.

The idea was that as you tuned across the CW allocations of the ham bands that the high-frequency/low-frequency selectively filtered audio, being fed to the stereo headphones, gave the sensation of the audio tones moving 'between' the listener's left and right ears as the receiver was tuned across CW signals (this presumes single signal reception where a tone is only heard on one side of the zero beat frequency). When the receiver was tuned such that the derived audio tones, caused by the CW signal, was at the 3 dB frequency of the filters then the audio signal levels from the high-pass and low-pass filter streams would have equal intensity and the listener would perceive the signal as being 'centered' between their left and right ears. As the receiver was tuned off that frequency, and the audio frequency changed, then the filtering action would result in the intensity of the audio tones being fed to the left and right headphones to change (in opposite directions) resulting in the perception that the signal was 'moving' between the left and right earphones.

From what I've been reading in the news threads it does not sound to me as though the binaural implementation, applied in the FLEX radio software, provides for this action but is instead a repeat of the artifice used many years ago in some Dynaco stereo amplifiers (circa the early 1970s) in which the phase was inverted in either the left or the right audio stream of a stereo audio feed.

Have I misread what's being implemented in the FLEX radios ?

- Paul, WB5AGF


  • Duane_AC5AA
    Duane_AC5AA Member ✭✭✭
    edited May 2018
    I haven't tried it in the Flex yet, but what you describe is exactly how Ten-Tec implemented it (although via DSP) in the Orion transceiver as a selectable option for CW.
  • Steve N4LQ
    Steve N4LQ Member ✭✭
    edited September 2015
    A phase shift....It reminds me of what they used to call "simulated stereo" Or those FM portables with "narrow" and "wide" stereo modes.....
  • Martin AA6E
    Martin AA6E Member ✭✭✭
    edited June 2020
    You might be getting I and Q audio to the L and R channels, which implies a 90 degree phase shift independent of frequency -- something like that. It's not a simple frequency pan as in the Orion AFAIK. I'd like the details from FRS! It would be cool to have a selection of BIN functions to play with.
  • Ken - NM9P
    Ken - NM9P Member ✭✭✭
    edited December 2016
    I would LOVE to have the binaural feature as described above. I read the same articles and have always wanted to do that. It would be nice to have an adjustable "swing" I.e. A variation that determines the center frequency and how far off each side takes the perceived signal to far left or far right. It would be really nice to sort out a pileup. When using a narrow filter, a small frequency change shifts a lot of distance. Whereas using a wider filter it would need a larger frequency shift to go all left or all right.
  • Paul, WB5AGF
    Paul, WB5AGF Member
    edited March 2017

    Here is an article by VE3VXO that sounds interesting :

          A Binaural Processor for Any Rig


    (I've been up much of the night trying to configure LP/HP audio filters for the left and right
      stereo audio channels on my PC using EqualizerAPO but so far it hasn't been willing to
      work like I wanted it to.)

    - Paul, WB5AGF      (I've had enough of this technology stuff
                                       - it's time for me to go ride my bicycle!)

  • Oxford English
    Oxford English Member ✭✭
    edited November 2017
    Question - can you get Binaural when operating remote, i.e. using USB headphones?

  • Al K0VM
    Al K0VM Member ✭✭✭
    edited December 2016
      Yes, seems to work with Remote here  too.
    AL, K0VM
  • Tim - W4TME
    Tim - W4TME Administrator, FlexRadio Employee admin
    edited March 2017
    For the current implementation of binaural listening mode, the left and right channels are 90 degrees out of phase from one another producing a wider sound stage or more spatial field of listening that can enhance weak signal reception.

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