Ok, I have two suggestions:
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Run the sketch I posted in reply #1 and post the output, as you go from the storage room to the window.
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Run the NeoGPS example sketch NMEA.ino and post the output, as you go from the storage room to the window.
The sketch in reply #1 shows how the "rules" I made for ublox are interpreted for your MTK chip.
The NMEA.ino example will show the entire satellite array it is receiving (from the GSV sentences), even before it gets a good fix. This should characterize what the MTK reports, and perhaps let us make a different set of rules for the MTK chip.