Read this: BBC HD: Nyquist Limit
Summary: Editor's note - Andy Quested was going to add this as a comment responding to tagmclaren's question about frequency gatings but as you can't put pictures in comments I thought it would be better to publish it as a new post Dear tagmclaren Thanks for the comment. What you are seeing unfortunately is an alias that's folded back at around 26MHz. Here is your picture with the original 25 and 30MHz gratings added - if you look at the off-air and original 25MHz grating you can see they line up but the 30MHz original does not match the off-air grating. - bbc.co.ukwww.bbc.co.ukBBC HD: Nyquist Limit…
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