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CW Sidetone via PC audio

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Lionel
Lionel Member ✭✭✭
in SmartSDR for Windows

This seems like a feature that could be added and would be useful to CW ops. At my home station the 6400 is connected to a router on my wifi network and the computer is on the same wifi network as the 6400. Using PC audio the soundcard outputs to powered speakers and works fine. There is no sidetone.

This matters because I do some further audio processing, mostly noise reduction. No sidetone makes CW impossible.

There seems to be no way to have CW sidetone thru the PC Audio. Is the issue latency between key closure and sidetone?

I do not use remote and all connections are local. I've been reworking the station audio for processing - this gotcha is a surprise.

Ideas? Crying towel?

Comments

  • g4ivv
    g4ivv Member ✭✭
    Options

    Hello Lionel,

    I assume you are using the keyer in the radio with the paddles or straight key plugged into the back of the radio?

    If so, what you are asking for is pretty much impossible to deliver, as the latency between the keyer in the radio and the PC speakers will make sending CW almost impossible (unless you are very very QRS hi).

    The only option is to route the sidetone out of the back of the radio (headphones or line out) and use an external, analog, audio mixer to combine the PC audio and sidetone before feeding to the powered speakers. You'll need to make sure that RX audio doesn't follow the same path to clash with the RX from the PC but I don't have experience in doing that, perhaps someone else can confirm this is possible. Or use an external keyer plugged into the back of the radio (radio Iambic mode disabled) and mix the sidetone from that keyer with the PC audio.

    I would always recommend mixing the audio in a hardware, analog, mixer rather than trying to do that in software on the PC becasue again you will run into latency issues in the PC audio path. Sometimes you just can't get better than an analog audio path! 😀

    Best 73,
    Jonathan G4IVV

  • KD0RC
    KD0RC Member, Super Elmer Moderator
    Options

    Hi Lionel, Yes, the issue is latency. Simon, NV0E has been trying to reduce sidetone latency in his RimuSDR application. Under Linux, and with a fast computer, he has reduced the latency enough to make it usable.

    Under Windows, it is not even close. There are two issues. The first is the total latency from key closure to sidetone output. The second is the consistency of the latency. It can vary wildly from one key closure to the next. This means that you can't easily compensate for the delay.

    It is amazing just how little latency it takes to completely throw you off. The faster you send, the worse the problem gets. At 20 wpm, a dot is only 60 ms long. A 15 ms delay is a quarter of that and is an unacceptable amount. We were getting worse results than that despite best efforts.

    Windows is just not a real-time or even a near real-time operating system, so I don't anticipate a good solution for this anytime soon.

  • Russ Ravella
    Russ Ravella Member ✭✭✭
    Options

    Hey Len,

    This makes me wonder about something. Maestro runs a dumbed down version of Windows as I understand it. And it has so much latency in it's voice monitor function it's totally useless (agree with your comment about a small amount of latency being a big deal and it has a LOT of latency). It was a well know problem in at least the early version "B" times and wasn't addressed at all in version "C" - it's still unusable. Flex has said it's because the audio is routed from the Maestro to the radio and back which you'd think they would have fixed (at least) in the new version "C" (which took over FOUR YEARS to produce).

    Do you think it's possible that they actually can't fix it because it's mostly being caused by Windows in the Maestro ?

    Thanks, Russ

  • KD0RC
    KD0RC Member, Super Elmer Moderator
    Options

    Hi Russ, hard to say… I have no idea what OS or processor is in the Maestro and I don't know how they create the sidetone. Without knowing the specifics, it is just a random guess. It is funny that the easiest mode to implement in an analog rig is CW, but it seems to be the most difficult in an SDR.

  • Russ Ravella
    Russ Ravella Member ✭✭✭
    edited July 8
    Options

    Hi Ken,

    Yeah, agree. Flex has never really explained how the voice monitor works in Maestro as far as I know and without that, it's just guess work. All I've ever been able to learn from them is they send the signal to the radio from the Maestro then send it back to the monitor function in the Maestro resulting in the delay. It's hard to escape the conclusion there's more to the story. Since the monitor tap occurs before any processing happens it can't be used to adjust anything. So why send it to the radio at all ? Very weird …

    Thanks as always for the response, Ken ! Russ

  • Lionel
    Lionel Member ✭✭✭
    Options

    Well, I had a brilliant comment on the topic but unfortunately I wasn't logged in. Poof - gone.

    Pretty clever of me.

    More coffee and I'll try for semi brilliant!

  • KD0RC
    KD0RC Member, Super Elmer Moderator
    Options

    Hi Russ, the monitor function is just the same as on old broadcast equipment from the beginning of radio. It is only there to provide a way to hear yourself in your headphones when speaking into the mic.

    Because Flex has the ability to run full duplex (FDX), there is an easy way to look at (and hear) your own signal over the air without a separate receiver. Ken, NM9P has some great YouTube videos on using FDX to adjust your TX Equalizer.

  • Russ Ravella
    Russ Ravella Member ✭✭✭
    edited July 8
    Options

    Hi Ken,

    Yes, exactly. It's supposed to literally be a "monitor" function, just to hear yourself when you have headphones on. And it doesn't need to be anything else because there's the super easy and effective way to adjust EQ, processing, etc via a second RX input. In my own station I can literally just choose an unconnected transverter port for RX and transmit as usual from my normal antenna and hear myself at just the right level. Then adjust away. Works perfetly.

    But the audio monitor in the Maestro does NOT work perfect - because of the totally unnecessary delay as described before. According to Flex, the audio is sent to the radio (where it serves ZERO purpose) and is sent back to the Maestro producing so much latency it's utterly useless as a monitor.

    What I don't understand is why they designed it that way in the first place since it makes no sense, and why they have never fixed it, even during the "B" to "C" transition (which took FOUR years - lots of time to fix it). That's why I asked you the WIN question.

    Anyway hope springs eternal …

    Thanks as always, Ken ! Russ

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