Remote (virtualized) CW

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Remote (virtualized) CW

Postby w-u-2-o » Sat Jun 15, 2019 2:05 pm

Remote/virtualized CW: running CW by connecting a key to your PC and listening to audio on your PC via VAC.

It has long been believed that remote/virtualized CW is not possible due to high signal latencies in a virtualized environment. However, this is not strictly true any longer. Remote CW with PowerSDR and Thetis ranges from "merely doable" to "provides perfect QSK performance", depending upon your operating environment.

Hardware requirements:

- Key or paddle
- 9 pin serial port (USB, built-in or PCIE card)
- Cable between key or paddle and the serial port
- Speakers connected to your PC
- Code oscillator (optional and/or not required--see below)
- ASIO-capable sound interface (highly desirable, required for QSK with Protocol 2)

Connecting the key or paddle:

Method 1, paddle/iambic key,
- In Setup > DSP > CW set Primary to COMx and Secondary to None.
- Attach the DIT connection to the DSR input on pin 6
- Attach the DAH connection to the CTS input on pin 8
- You can use usually use the RTS output on pin 7 as the common connection, the DTR output on pin 4 can also be used.

Method 2, straight key or external keyer output,
- In Setup > DSP > CW set Secondary to COMx and Primary to Radio or None
- In Setup > DSP > CW set PTT Line to None and Key Line to RTS
- Attach the key across the RTS output on pin 7 and the CTS input on pin 8
- (Alternate arrangement: set Key Line to DTR, attach key across DTR output on pin 4 and DSR input on pin 6)

Connecting speakers:

See my VAC tutorial here:

For optimum performance you want to use an audio interface that supports the high-speed ASIO audio driver. A very good choice is the Behringer UMC202HD, which seems to have the most stable drivers and is at a compelling price point, but there are many other choices. You must spend quality time tweaking your buffer and buffer latency settings to the minimum possible on your system. With Protocol 2 and ASIO always set the PortAudio settings to zero. You also must use either the low latency filter setting (any size) or a linear phase filter of no larger than 1024.

For QSK under Protocol 2 an ASIO interface is mandatory. Normal Windows sound drivers are just too slow.

Configurations vs. available perfomance (PowerSDR implies Protocol 1 firmware, Thetis implies Protocol 2 firmware):

PowerSDR with normal Windows sound drivers--you can send and receive, but latency is pretty bad. No QSK. There will be no sidetone unless you attach a code oscillator right to the key or paddle.

PowerSDR with ASIO sound drivers and interface--with properly adjusted driver and VAC settings, perfect performance. No QSK. Again, if you want sidetone you have to generate it locally yourself the old fashioned way, with a separate code oscillator.

Thetis with the new QSK feature turned off and normal Windows sound drivers--same as for PowerSDR above.

The following configurations require ANAN-200D, 7000 or 8000 series radio hardware.

Thetis with the new QSK feature turned on and Windows sound drivers--too frustrating to use due to latency, not recommended.

Thetis with the new QSK feature turned on with ASIO sound drivers and interface--with a properly adjusted driver and VAC settings, perfect QSK performance. And perfect sidetone is obtained from your own signal coming back into the radio full duplex.

Thanks to recent work by W1PA (software) and N1GP (firmware), this last configuration is really a stellar performer. Set up properly you will enjoy using it quite a bit! :)


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