[R-390] Filters, the little wire

[Tisha Hayes]

That tiny than a hair little wire that runs through the center of the coils
is very important. Think of the coils like speaker coils and then think of
that little wire like the speaker cone that moves when the magnetic forces
tug on it.

That little wire is coupling the 455 KHz signal to the stack of disks that
are mechanical resonators. At the other end of the filter there is another
little wire that mechanically vibrates and those coils pick up the
disturbance in the magnetic field and translate it back into an electrical
signal.

If you break off that tiny little wire I do not know of a good way to
mechanically reattach it to the filter. Think of it as being a critical
dimension, size, space and attachment. A blob-o-glue or a tack weld or
solder change some very important characteristics (resonances) of that
magical little wire and how the mechanical motion gets transferred over to
the stack-o-disks.

That entire stack of disks is moving around at 455 KHz so you can also see
why mechanical isolation is so important to the filter guts. Also the foam
goo/powder/whatnot ends up changing the mass of the disks and will shift
the resonant frequency (just like a musical instrument would be detuned).

Whatever foamy suspension devices you put into the filter should be
supporting the coils and not directly touching the mechanical resonator
disks. That changes their mass, shifts their frequency and attenuates their
motion.

Goo we can clean off, coils we can rewind, broken magical wires or mangled
stacks of resonator disks; we are out of luck.

-- 
Ms. Tisha Hayes/ AA4HA


*"neque est alter hujus universi locus quam anima"*
*('For there is for this universe no other place than the soul or mind')*
*-Arthur Schopenhauer*