It doesn't matter how well you can read the screen, a combat radar display lacks the detail to distinguish one type of aircraft from another, and the processor inside the radar itself doesn't have the ability to process data like that either. When someone says "the echo of a 777 and an Antonov are easily mistaken", I can instantly see someone trying to sell you something. Either he wants hits on his blog or he hopes someone will hire him to be an "expert" like most of the ones you can watch on CNN. What it proves to those who understand weapon systems of this nature is that he's making it all up.
Of course Ukraine is going to say it came from Russia. What else would you expect them to say? I didn't hear the US advertising about how their soldiers were being killed by the very weapons they had equipped Al Qaeda with back in the 70's and 80's. No one will admit it's their own stuff.
It may have been Russian. Putin may be behind everything. These are possibilities no one can deny. I have no problem with advancing a theory. But people speaking as though this is gospel, as though Ukraine, Europe and the US would NEVER lie and Russia is the epitome of evil. It's a biased opinion formed precisely because of how the west views the Cold War. To talk about Soviet and Russian propaganda while you repeat the kool aid you're getting fed by mainstream media (that wants to sell newspapers), online bloggers (that want to get page hits), and talking points from governments with a history of lying to people (Bay of Pigs, WMD's in Iraq, etc) is pretty hypocritical.