Thursday, 1 October 2020

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.

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.





  1. Hi !
    Very good, but did you use the cat system and how with the main and sub

  2. Yvan, thanks.
    I wish I could.
    For me CAT only works on the main band.
    That is as far as I know, maybe some trick can be found like this one with the audio, but I do not think so.
    The way I have it set up is by pressing the top AF knob as a button (Marked M/S) that changes over frequency, mode etc., between main band and sub band and keeps the CAT correct for the main band.
    There is no CAT working here for the sub band, so I do not post that to the cluster as it could show the wrong band. Also changing frequency on the sub-band software does not change the sub-band frequency on the rig.
    So only CAT on the main band, unless somebody can find an answer to that too!

  3. Great solution!
    Are there both mic and speaker on Main and Sub band?
    Thomas SM0YOS

  4. Hello Thomas.
    The best way I can explain it is that the 9700 is a transceiver with an extra receiver for a second band.
    With the transceiver you can transmit and receive with CAT control on one Main band.
    With the extra receiver you can receive on a second Sub band band, but with no CAT control.
    So you cannot transmit on the Sub band or use CAT control.
    You can receive data signals from them both at the same time on a PC using both channels of the USB audio link.
    You can only transmit on the Main band, you cannot transmit on the Sub-band which is receive only.
    You can swap the pair of frequencies between Main and Sub bands with one button press. You might do that if you hear something on the sub-band you want to reply to.
    I find I need to watch it carefully when switching fequencies as it is easy to get mixed up about which one you are transmitting on.
    I think that is right!
    73 Jim

  5. Hello Jim,
    Thanks for your answer.
    Just one more check... maybe stupid, already answered?
    When transmitting on the Main band can I receive/listen on the Sub band simultaneosly. I plan to use IC-9700 for duplex communication to the QO-100 Oscar satellit, IS0GRB Winlink via VARA.

  6. I mean can i have the soundcard splited between the tranceivers.
    Microfon to the Main band and the Speaker to the Sub band

  7. Thomas
    I have tried this tonight.
    I moved my 70cms antenna to the IC-9700 and set a weak beacon up to receive in the Sub band.
    Then I set 2m to work on FT8 on the Main band. I found that I can TX on the 2m band and then RX on the 70cm band. This is duplex TX Main band 2m/RX Sub band 70cm.
    I decided to try simultaneous TX on 2m and and RX on 70cm and this worked. I called CQ on 2m while receiving and decoding the beacon on 70cms. I was called on 2m by MM0GHM and worked him on 2m and I decoded the beacon on 70cms at the same time. The intervals are different (15sec FT8 and 60 seconds JT65) so a fair test both ways. So in this case the TX data was traveling one way on the USB cable via one channel and the RX data was using the same cable in the "other direction" on the other channel.
    I think you can work split between bands TX/RX with TX on main and RX on RX. It also looks like you can do both simultaneously and listen for yourself coming back from the satelite. This will depend on your antenna separation, frequency separation, filters and power. I found I could do it with 50W on 2m, but more noisy on 100W. Higher power on the Main band and the Sub band receiver started to de-sensitise (of course as my antennas a very close). But the beacon on 70cm still decoded at 200W TX on 2m.
    Hope this helps.
    Jim GM4FVM

  8. Sorry Thomas. Could not get Blogger to publish my reply, but it has now - see above.

  9. When I wrote:-
    I think you can work split between bands TX/RX with TX on main and RX on RX.
    I meant:-
    I think you can work split between bands TX/RX with TX on Main Band and RX on Sub Band.

  10. Thanks again for a very useful article.

    I've been playing with all sorts of settings on my new IC-9700 today. So far, on the audio side, I've managed to bring out one audio channel from the 23cm receiver and route it to SpectrumLab to give me a better visual image of the audio from the signal of GB3MHZ I'm finding the display on the radio a bit small, but just about usuable, except that the fixed audio filters 'scrunch up' display on CW. I guess using SSB would increase the audio bandwidth displayed. I'll also work through the menus to see if the height of the audio scope can be increased on the screen of the IC-9700.

    I've not quite sorted WSJT yet. I can get the CAT to work but there seems to be too much audio and I've not yet figured out how to turn it down.

  11. Update - I wondered what "EXPD/SET" did and it increased the height of the Audio Scope. So, another lesson learned. :-)

    Cheers - Dave (G0DJA)

  12. Another update. I've now managed to bring out both audio lines through the USB connection from my IC-9700and have set up two instances of WSJT-X. One for 'Main' the other for 'Sub'.

    I also discovered how to turn the audio output level down to the USB connector. The answer was on page 13-2 of the basic manual. The level is controled by selecting
    Menu >> Set>Connectors>USB/IF Output.

    Then, press the "USB AF/IF Output" option, then "AF Ouput Level" and either use the + or - buttons on the screen or turn the main turning knob left or right. I found that a setting of 10% brought the level to both instances of WSJT-X down to 30dB on a quite band for 2M and 23cm.

    I'n the past I have found that MSHV seems to need higher levels of audio input, so you may need to tweak the value for other software.

    The fact that there is an 'IF' output is also interesting, as it suggests being able to monitor the receiver IF as a 'Panadapter'. Let's hope someone writes a suitable bit of software to be able to see this on a PC or separate display...

    Cheers - Dave (G0DJA)