Paul_dbnut

Mr John!!! You are a star!!! 😂

I came back to the Kiwi forum after six-plus months away, and what do I find? You have resurrected a 70-year-old forgotten/ignored technique I've been trying (unsuccessfully) to promote for over a year. And longed to experience since reading about it in my teens, 60 years ago!

Your "SAS", or something apparently equivalent. Coherent lower/upper sidebands demodulated and presented to left/right ears.

This was often referred to as "binaural" in the literature, but that's a term hijacked for two other different audio techniques in the last 20 years or so. Now I think of it as "sideband binaural".

For me, the brilliance of SAS is primarily in spreading all the (non-coherent) noise across the sound stage, leaving the wanted channel centred and allowing the brain to focus via the "cocktail party effect". Adjacent channel interference tends to come from the sides as well.

A more subtle benefit is often found for co-channel stations with small carrier offsets from nominal. The tiniest spatial separation is enough to improve aural discrimination so much more effectively than with plain AM or even SAM. Sometimes even much weaker stations can be resolved.

In my opinion this is an indispensable tool for serious DXing. I hope many other listeners are going to explore and enjoy its capabilities - and the word gets around to other potential customers.

If you've researched the topic you will know that KiwiSDR is unique. Binaural sideband AFAIK has never been implemented in analogue radios. And NO OTHER SDR program offers this feature. The couple that provide a "BIN" or pseudo-stereo function do something completely different, completely missing the potential achieved by Kiwi. There MAY have been just one SDR going down the same track, but that looks like a dead donkey now.

I'm very curious to find out how you implemented this (I did it with Hilbert) and have a couple of ideas arising from my experiments. Don't know if you feel like chatting?

Thanks to Ken for his post that directed me here, and to you for having the inspiration and making the effort to provide it.

All the best

Paul

Oho, John, maybe Teensy added that after I looked in on it a long time back, or I just didn't understand what it was doing. Can't remember.

Re: I-Q "pseudo-stereo", that's something various people provide (under various names), but if you listen carefully it has the same "disembodied" character as wrongly-phased stereo - you can't get a solid focus on individual components. It's a waste of time, except as a special effect.

SAS or "sideband binaural" "does the business" because the 90 degree phase shift (Hilbert) in one channel as it were compensates for the 90 degree quadrature of Q. I'll call the result Q*.

Then summing I+Q* gives LSB and I-Q* gives USB, according to the standard (now almost never used) "phasing method" of sideband selection.

With this, sending phase-coherent LSB to L and USB to R we're really motoring because (under perfect propagation and DSP) the phase-locked station is 100% centred in your head. Noise (non-coherent) is spread across the sound stage (unlike with plain SAM). Adjacent channel muck is off to the side. Effective SNR is greatly enhanced, maybe by 6 dB.

Next, the Luxembourg effect spoils this, up to a point, with the wanted station wandering around a bit. But your brain still tracks it OK.

Next again, a co-channel station can often be distinguished by slight offset in position or (maybe most often) by wandering around - so the brain gets a bit of help here as well.

The Spanish or UK Single Frequency Networks (SFNs) on MW are a very interesting special case. A jumble with AM or SAM can sometimes be clarified a little with SAS.

And lastly, something you don't provide is free vernier tuning to override the PLL. A range of +/- 10 to 50 Hz would cover most MW carrier offsets and, with a resolution of about 0.1 Hz, allows you to "tune in" individual offset stations. That brings them one by one centre stage (albeit with slow wandering) and can emphasise weaker stations in the presence of significantly stronger ones.

That really does work. Using Gnu Radio Companion on IQ recordings, I've resolved both a US plus a Canadian station on one channel underneath a much stronger local station. It's painstaking work, but that's DXing for you.

I'm not saying this is necessarily the best technique for all purposes - for example the recent SDR# channel cancelling is a stunning piece of work. But it's a simple "upgrade" for any SDR software and has never been generally exploited.

One last point. For general listening SAS has no advantage over SAM, and may even be inferior. But it is a specialist tool that performs miracles (well not quite). And its value cannot be appreciated from only a casual glance - you have to listen and get used to what it's telling you. And yes, some listeners may feel uncomfortable, a bit disorientated.

Sorry if I've bored you. I'd hate for this to be a "button" that no-one understands and just gets passed over.

@Bjarne "I am surely a minority in that respect!"

IMHO apart from top-flight DXers such as yourself, there are plenty of dabblers like me who just love to play with these fancy tools 😁.

System telemetry is as old as spaceflight, probably older. Surely the low-bandwidth data involved could be multiplexed onto any data channel, or on a special admin-only dedicated channel?

Given the low cost of sensors, some key electrical parameters would seem to be a worthwhile fit. For a few dollars more, we could have temperatures (multiple), pressure & humidity too - not a bad idea for any kind of equipment mounted outside the normal domestic environment, or even within.