"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