It's possible but the problem is I'm on the 1st floor of a 5 story building in a dense European city center, and all the buildings around me are of similar height. Meaning that the signal will basically be absorbed by the buildings around me (best case) and/or the neighbours' electronic equipment (worst case :) ). There's just no way to get a decent signal out from here. The distance to the next buildings is also way shorter than 1 wavelength on HF, the street out front is only 1 lane wide with a tiny footpath (European city...). So the gap isn't even wide enough. It just won't get out and will probably cause a hell of a lot of interference problems.

Since I don't have any HF equipment I didn't deem it wise investing in some for this reason. I do have a receiver but the inbound signal is also really meh.

With 2m/70cm I have better luck because the repeater is nearby on a tall mountain and the wavelength is short enough to be able to bounce around and get out.