Main and sub band USB audio output with the IC-9700.

Two postings ago (here) I explained how I was collecting a second audio stream from the IC-9700 to route to a second decoder in my computer, allowing dual band FT8 (etc) decoding.

I did this by using an analogue audio stream and it proves that it works.

I had read in a review that the IC-9700 creates one digital stream for the computer via the USB and that any second stream for the sub band would need to be taken out by analogue audio. I believed that when I read it. The Icom manual said nothing about it at all, and certainly never suggested that a second audio stream was available via the sound card and USB.

Imagine my surprise then when Greggor posted a comment on an earlier posting in this blog here to say that it is possible to get both streams via the USB. Greggor's comment was:-

Do you mean you can't get the sub band audio through the inbuilt sound card ? By default - windows sees the inbuilt sound card as a MONO microphone. If you go into the advanced audio properties and force this to 2 channel - you will have main and sub coming through. Left & Right.

https://klop.solutions/stereo-audio-from-ic-9700/

Yes, I did mean that at the time, but you are right, this is possible, and I have now done it. The link given my Greggor sets this out. I did it my way by working it out myself before reading the link, just to see if I could do it. I could do it, and it works. I explain what I did below. Thanks Greggor.

First, I read all of the IC-9700 manual and advanced manual. There I could find nothing to say that this was possible, nor anything else about the audio output via the USB. The whole subject is missing. I suppose this may be because Icom are not responsible for Microsoft/ Apple/ anybody else's operating system, our computer layouts or our USB drivers (though they do provide USB drivers). If that had been in the manual I might have noticed it by now.

However, I am not going to let Icom off that easily. They did not need to understand anything about my computer to indicate in the manual that this was POSSIBLE. All they needed to say is that two digital audio streams exist, or are enabled via the sound card and USB. If that is in those manuals I cannot find it.

This second audio feed has been coming out of the IC-9700 via the USB for more than a year, and I have been ignoring it because I did not know it was there.

Moving on, once Greggor pointed this out I set about proving it my way. That means I understand how to do it. As usual I went to Control Panel and selected Sound .... (click on the images to enlarge them if you need to)

"Control Panel" in Windows with the "Small Icons" view.

As always I view Control Panel in "Small Icons" view as it makes it easier to see everything plus I am old enough to remember when it always looked like that. You can get to the sound settings other ways, but this is the way I do it. I like defaulting back to Control Panel as it gives easy access to both "Sound" for this type of thing and "Device Manager" for COM ports and lost USB connections.

OK, selecting "Sound" allows me then to select "Recording" which is where the audio comes in, and then the USB input I am using for the IC-9700 - in my case "Microphone USB Audio". I then selected the "Advanced" tab where I found that Windows has by default selected a one channel audio stream. Change it to two channel, in my case "2 channel, 16bit, 48000hz (DVD Quality)". I clicked "Apply" and I had enabled main band on one channel and sub band on the other channel.

Selecting a two channel stream in the "Advanced" tab for the USB sound card input

Then I shut everything down in the Control Panel.

Although I use Windows, I expect that Apple or other operating systems have similar option screens.

My next thing to figure out was which channel was which. Effectively we are using a stereo sound stream for two different signals. One band is "right" and the other is "left".

A quick bit of juggling showed me that, for me anyway, main band is left. In WSJT "Settings" that worked when set to "Mono" by default, but I set it to "Left" and it also works there.

Channel selection in WSJT-X - Input "Left" or "Mono" both gave me main band.

As my sub band decoding is done in MSHV I needed to set it up to right channel. That setting is in "Options" then "Sound settings". Just click "Right Channel".

Channel selection in the MSHV Sound Settings tab

Job done. Not only does it work, but it works better than the analogue lash-up, and saves another sound card and cable, plus I get my on-board loud speaker back. By avoiding a digital- analogue- digital conversion there is less noise.

GB3NGI on 144MHz via the (now-digital) sub-band

So now thanks to Greggor I have a fully digital 2-band decoding receiver. In my case this is 144 and 1296 MHz bands simultaneously. You could use any two bands, but not two frequencies in a single band.

The manual does not say it is not possible to have two digital audio streams, it does not say it is possible, it just does not cover it at all. Yet there are pages and pages of irrelevant bull-crap about logging what speed your radio is moving at, or what height the receiver is, while surely the IC-9700 is more likely to be used as a fixed DX, moonbounce and satellite transceiver. Still, you never know - I might take up using DStar repeaters from a hot air balloon. That is the obvious next step for me to take in my radio journey. 

If I was in a hot air ballon I might be able to work Montrose (read the whole blog history to understand that one).

How any cross-band digital mode operator could have worked efficiently without this knowledge I do not know.

So thank you to Greggor and I have now got this resolved and I am back to an all-digital system.

It almost seems that the S/N on the separate main band stream is better than the figures on the mono settings for the single mono digital stream. 

Surely I am imagining that.

73

Jim

GM4FVM