Thetis QSK Delayed Sidetone

W4ATL
Posts: 3
Joined: Tue Mar 09, 2021 9:14 pm

Thetis QSK Delayed Sidetone

Postby W4ATL » Thu Nov 11, 2021 6:23 pm

When using QSK with Thetis you have to turn off the Sidetone so that only the routed TX signal tone comes through. But it is delayed making it difficult to use paddles at high speed. Is there a way to turn off the routed TX signal and use only the sidetone that is not delayed?
W4ATL
Posts: 3
Joined: Tue Mar 09, 2021 9:14 pm

Re: Thetis QSK Delayed Sidetone

Postby W4ATL » Sat Dec 04, 2021 4:24 pm

The delay can be reduced by going into Setup/DSP and setting Filter Size/CW = 1024. This is at the expense of filter sharpness but to me it is worth it. The delay is still there but much improved. Perhaps a lower number can eventually be implemented.
W4WMT
Posts: 158
Joined: Sun Apr 09, 2017 10:12 pm

Re: Thetis QSK Delayed Sidetone

Postby W4WMT » Sat Dec 04, 2021 10:54 pm

W4ATL wrote:Is there a way to turn off the routed TX signal and use only the sidetone that is not delayed?


The only way to turn off the routed TX signal would be to mute the receiver during each cw element. Since all cw generation is now being done in the fpga, there would not be a software solution to do what you ask. I believe there's a way to do this in gateware, but that's waaay above my pay grade. Perhaps there are some bright & talented GA Tech students, that have some recently acquired OpenHPSDR derived hardware in their club station, that could engineer a solution?

73!
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w-u-2-o
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Re: Thetis QSK Delayed Sidetone

Postby w-u-2-o » Sun Dec 05, 2021 4:08 pm

Firmware generated sidetone should still be working perfectly. If you attach a speaker or headphone to the ANAN hardware, and a key also, then things should be just peachy.

The problem is with sidetone via VAC. The QSK full duplex fix is a Band-Aid, albeit a very clever and welcome one. Fixing this properly is conceptually trivial, with low technical risk, and requires no firmware development. If we require the key to be attached to the PC, something the software already supports very well, sidetone can be injected into the VAC audio output with extremely low latency, almost certainly less than 10ms.

If one wants to attach a key to the ANAN hardware and listen via VAC (not sure why you would want to, but still...), even that does not pose a huge technical challenge. Flagging key down/key up events in the high priority UDP data stream that already comes from the hardware would allow very low latency sidetone in the VAC audio stream using the VAC sidetone injection proposed above. However this would require firmware changes.

All that is needed is someone who wants to tackle low latency sidetone injection into VAC, and operators willing to attach keys to their PCs via the serial port mechanism already provided.

Philosophically, it was never clear why the original design went in the direction that it did. This being software defined radio and a thick-client architecture, it never made sense to add audio and key/paddle interfaces to the RF hardware unit. Perhaps there was a belief that these things could not be implemented with reasonably low latency with normal PC interfaces, but now we know that is not the case.

BREAK

Why do you refer to firmware as "gateware"?

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