HAARP does work at 2750 kHz and I have seen them on this freq several times. I saw the signal you have images of and would have to say yes, it was HAARP, but to be honest that was the weakest I have ever seen HAARP, so at first I was somewhat skeptical.
Prior to being on 2750 last night it was up around 5660 and up with a very interesting pattern, I do have a screen shot of it on the PC at home, but nothing online of it yet.
T!