Nukes are more like submarines: once you've heard one, you can recognize it again. If there's a new design, it can take a while to develop an understanding of what it looks like.
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Yes, precisely right, as I understand these things.
If anyone's curious, I recommend visiting the High Energy Weapons Archive to learn more about general nuke characteristics and test detection methods.
Home Page -
<http://nuclearweaponarchive.org/ >
Nuke Test Info Page -
<http://nuclearweaponarchive.org/News/Bigsubpages/Bigsubpage25.html >
.d.