In the DVB-T constellation chart, there are occasional, irregular, sporadic flickering points in the blank spaces between adjacent points.
The flickering points flicker within a fixed range, with an average EVM of 2 and a peak EVM of 100. The points in the pilot circle occasionally flicker. There's the video showing this problem more clearly. Link here: https://drive.google.com/file/d/1ZAWoIZgF4RGCz75C5u1ZUaTZzBqFJO0y/view
What could be the reason and solution for this?
These are your four QPSK constellaiton points, even at the same distance, but offset.
So, something might be going wrong with the offset compensation in the receiver. Or, there is an overly aggressive addition of an offset that is too fast and too strong to smoothly compensate. I don't see how that'd happen in a sensible OFDM receiver; so, maybe you're having a strong interferer and your measurement device isn't good at dealing with interferers. That might well be realistic, as intermittend narrowband interferers which could lead to such offset on individual subcarriers, would at most erase the bits on that one subcarrier – something that might be easier to catch in FEC than by implementing more intelligent interferer cancellation – especially because DVB-T happens in bands that are protected from narrowband interferers by law.
