I'd like to introduce my soul project, https://ssbtrainer.com
It throws the pileup a DX usually encounters at you, and the stations will try all sorts of tricks to get your attention - from cranking up their amp to chasing you around the waterfall.
It does real-time RIT, it lets you send partials (and call by numbers). If you ever missed the lovely sound of an OTH or someone whistling ola ola over your QSO - I have you covered.
It works great on mobile phones and quite well on desktops - I've taken special care to have details pop up, from keyboard shortcuts, to achievements and secret callers.
Sadly my server has been hammered lately, so you might not get a spot in the DX mode right away.
You can, however, practice callsigns one by one, at higher SNRs and with less obstacles - but where's the fun in that? That's just... routine practice before IARU?
The most interesting bit has been the DSP needed to make it sound believable. I know the theory: what HF noise ought to do, how an aurora distorts a signal, how an amplifier should mangle things when asked impolite questions. But making it sound right is where the wheels come off.
It is not just random filtered noise, or frequency-wobbling delayed waveletsl, or ducking everything else so the amplified one looks important. The bloody thing has to misbehave in a familiar way to the trained ear.
Richard
DL9DX
Ian