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#4
February 19th 06, 02:32 AM
posted to rec.radio.amateur.boatanchors
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May be OT - Mechanical Collins filters
"Mike Andrews" wrote in message ... Paul P wrote: I am new to Ham but a multi-decade experienced technician. BUT What is a "Mechanical" Collins filter? I know what they are used for but why are they called Mechanical? I get an image of a tiny squirrel running in a cage..... It's not quite like that. But they do have moving parts, though not quite as you imagine them. Put a transducer on one end of a can to convert signal into mechanical motion. Have it drive a thin, stiff rod along the axis of the rod. Along the rod, at regular intervals, solder or weld the edges of a few (maybe as many as 5 or 6) discs of metal, so that the discs are all concentric. Now solder or weld another thin, stiff rod to all the discs, 180 degrees away from the first, and put its free end into another transducer at the other end of the can; the second transducer converts mechanical motion back into signal. The center frequency and bandwidth are determined by mechanical properties of the discs. Collins developed these as small, sharp filters with steep skirts, relatively-good passband ripple, and tolerable loss. See http://www.rockwellcollins.com/about/additionalproducts/collinsfilters/page4667.html for information on more modern mechanical filters as well as the old "drumhead" filters I describe above. A Google search on "collins mechanical filter" will produce a plethora of useful hits, too. 73, de -- Mike Andrews, W5EGO Tired old sysadmin Mike, That makes totally sense. I never imagined a filter made up like that. But it makes total sense when you see it. Now I am really curious. Duh. I should have Googled it. Thanks, Paul kb3lzp www.ppinyot.com |
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