Free e-Book version of The ARRL Antenna Book
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Many thanks to Alex (KR1ST), on Mastodon, who notes that the e-Book version
of The ARRL Antenna Book 25th Edition is free on the ARRL website. Simply
go t...
2 hours ago
Here you go Bill.
ReplyDeletehttp://www.eso.org/public/videos/vlttrailer2009/
73s de WP4BQV/VQ9BQV
Anybody know what the laser was doing? Calibrating distance to a geo-stationary satalite?
ReplyDeleteThe laser is projecting a "virtual star" in our atmosphere, allowing the telescope to computationally subtract the "twinkle" caused by turbulent air from the other stars in the image.
ReplyDeleteHi Bill
ReplyDeleteIn 1992 I was invited to go to the factory that was polishing the mirrors for the VLT. It was a very interesting trip and the technology being used was fascinating. To prove out the process, they started by grinding a concrete blank. It was the smoothest piece of concrete you had every seen!
The mirrors are also ridiculously thin and would break if it wasn't for the adaptive supports behind them. Really great trip and a total surprise since I was really visiting a sister company.
73 Paul M1CNK