@selfin
Many thanks for your efforts, it is one of the most informative posts in the past 500 (if not 1000).
I would have assumed that an aircraft would NOT be able to cross the peninsula without appearing on PSR but apparently this is not the case (though we do not know how many military radar sites are there that are unpublished in the AIP).
... whilst there might be a radar return, would it necessarily be recognized ...
selfin's diagram demonstrates that
theoretically even a T7 could cross the peninsula without showing up on radar. However if it does show up for any period, I'm sure the radar return would be investigated, especially if ATC is aware that there is a missing aircraft. Of course there is always the possibility that a weak return beyond the effective range was recorded, but not displayed. ATC radar screens no longer show actual signals from the radar antenna, rather a computer generated image that is based on the processed signals. There are very complex algorithms to filter out backscatter and other noise (one of the most closely guarded secrets of military radar manufacturers), and whether a faint real target makes it on the screen will be a function of whether the computers can distinguish between noise and target. Also the radar display may be set for a certain range, so even if the actual radar antenna captures a more distant target, it will not necessarily display on the screen. However the primary signals are stored for a period of time, to be retrieved in situations we are now discussing. Also as it had been discussed previously on this thread, the military operates more sensitive radar stations the existence of which are not necessarily in the public domain, and their data may be available. Using more sensitive (hence slower) algorithms much more may be retrieved from the raw signals than what was originally displayed on the screen. Undoubtedly this had already been done, and may have prompted the search along the western coast of the peninsula.
However this is not an exact science. There might be some very faint radar returns that may or may not be the missing aircraft, first they need to be cross checked against other identified traffic. Also these faint signals at the edge of the theoretical range usually don't form a continuous track, but are intermittent pings as reception conditions fluctuate between poor and nil. I can easily envision that Malaysian radar picked up something that
might have been MH370 given the place and the time, but authorities would not want to make a public statement about it in case it turns out to be a cold trail just like so many others - however the possibility is high enough to allot some SAR resources to follow it up, especially after three days of searching in the primary area yielded nothing.