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Homemade output transformer for push-pull 6SN7 or equivalent tube. Silicon steel split C-core. Handles +30 dBm at 20 Hz! Has tertiary winding for Pultec amplifier feedback circuit. Compatible substitute for the Peerless S-217-D.
St Paul's Literary and Educational Society, Bennett Street Sunday School. Odds and Ends is the handwritten manuscript magazine issued by the society. The editions cover contemporary events of national importance like the Crimean War and the First and Second World Wars, and leisure activities like music, art, literature photography and holidays.
The laser spot at ~3 m from the laserhead. Obviously, this is a long way from being a Gaussian profile, but it is still evident that the divergence is quite low for a transverse electrode nitrogen laser. Ignoring this, we're looking at about 1 cm per 3 m. Again, ignoring the fact that this is not a Gaussian profile, can anyone offer the formula for calculating the divergence of a laserbeam (in milliradians) based upon the spot size at a given distance from the laserhead?