Bi-Aural or Binaural Reception

Quadrature techniques for selectable sideband demodulation, akin to the once-popular phasing method for transmitter sideband generation, have been known for many years.

Norgaard (W2KUJ) described a practical design in 1948 (or a little earlier) that was quickly developed as the add-on “Single Sideband Selector” type YRS‑1 (with 14 valves!) converter for communications receivers by the General Electric Company of America.

This allowed selection of individual sidebands, or both (with a locked oscillator this was equivalent to our familiar synchronous AM).

As delivered, the YRS‑1 routed audio back to the receiver AF stages. However “this truly wonderful gimmick” was promptly modified by one employee, George H Floyd: the “Lighthouse Larry” editor of G-E Ham News (an anthology of his SSB-related articles was published as the Sideband Handbook).

That modification delivered sidebands separately and simultaneously to split headphone channels, described as a binaural system in a G‑E Ham News from 1951.

Dinsdale also reviewed an unmodified YRS‑1 in the July 1948 Wireless World but nowhere hints at the possibility of binaural listening.

From the early 1970s onwards Pat Hawker (G3VA), in his Technical Topics column for the RSGB journal Radio Communications (and occasionally in Wireless World), was a frequent commentator on the technology and consistently referred to it as “bi-aural”. Nowhere does he appear to confirm having first-hand experience of such equipment.

Confusingly, the term “binaural” nowadays more usually refers to a completely unrelated sound recording technique, but even this is often called “bi-aural”.

The CCIR Study Group 10 compared various detection methods, rating their “relative effectiveness” in dB for different modes, and the results were tabulated by Haviland (1969, EBU Review) as follows (where we have edited the mode abbreviations slightly and re-ordered the rows):

Mode Envelope
detector
Slope
detector
Product
detector
Select*
product
Locked
loop
Bi-aural
DSB+C (10 kHz) -3.2 -6.5 -3.2 -3.2 +2.8
DSBC-C (10 kHz) +7 +10 +10 +16
NBFM (10 kHz) -20.4 -7.4 -10.4 -7.4 -7.4 -1.4
SSB+C (5 kHz) -3.4 -0.4 -0.4 -3.4 -0.4
SSB-C (5 kHz) +10 +10 +7 +10

* What can “select product” be?

From these figures, and the favourable comment it has generated at various times during the last seven decades, we dare to hope that SDR technology will bring about a resurgence of interest in binaural.

 

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Wish-List for SDRuno

I was prompted to write this after an interesting post in the Facebook group for SDRuno (https://www.facebook.com/groups/sdruno) by Nizar Ben Rejeb on 4 March 2018.

Anyone who takes the trouble to study “Studio 1” might agree with me that its designer came up with a great DSP engine presented in a very attractive GUI. For one reason and/or another it did not reach its full potential.

SDRplay, with no own-label software, saw an opportunity and “rescued” it from undeserved oblivion. In a very short time they have delivered an impressive number of fixes and improvements, and succeeded in making a re-branded “SDRuno” the best-documented software in its class.

That is all the more creditable seeing they are a small-ish company with limited resources, charging no separate licence fee, and even permitting restricted use with “alien” hardware.

Here is not the place to debate SDR software licensing models (though I want to go on record as having huge respect for Simon Brown’s free SDR Console) but we have to accept that the pace of SDRuno development is going to be steady, not a sprint.

I agree there is plenty of scope for extending the program (my own wish list is long). However  my priority would be to address fundamental weaknesses in interface structure, dealing with issues such as:

  • rationalising the excessive number of separate Windows (killing off MAIN, EX and REC, for example, and recognising the unity of RX, SP and AUX for each VRX by creating a container with layout options)
  • improving ergonomics by more logical grouping and styling of controls within and between windows
  • providing easier access to options with additional configuration controls and better use of context menus
  • overhauling the whole menu structure and offering more intuitive access to functions (e.g. saving a workspace)
  • simplifying window management while retaining flexibility

The last example is a long and very difficult project in itself, but there are now many programs that combine ease of use with flexibility, using a combination of techniques such as resizable panels with a variety of layout options, tiling, pinning, docking, collapsing and floating individual Windows, with clever aids to customising the overall window arrangement.

We can find many examples out there of great interface design to inspire thinking, including (aspects of) the FlexRadio software (mentioned by Nizar) and TitanSDR. With the right investment, SDRuno could become the gold standard!

Only my lack of the right skills stops me from volunteering!

Very best wishes (to the SDRuno Team and all their users).

Best-ever stands for Apple iPad?

Here, it feels as if iPads have been around forever. However checking Wiki tells me Apple brought out the first generation only in 2010, following up with the “2” just under a year later. I didn’t want or need one at first, but in 2013 dipped my toe in the Apple pond with a reasonably priced iPad 2. Umm, mainly for TV and hi-fi remote control.

As these things often do, in time it found other uses and so a Bluetooth keyboard/stand moved in with us. Well, it was good at what it was designed for, but wouldn’t let me operate in “portrait” (long side vertical) unless I was laid on my side. Continue reading