Behold, J M Noeding signalled from keyed 4-1000A filament:

On Thu, 15 Jul 2004 15:26:54 GMT, "Rick Karlquist N6RK"
wrote:

The filters in my article were purchased in 1995. Note that they are
10.7 MHz, not 455 kHz. Ceramic filters are alive and well and still
available at Digikey and Mouser.

Rick N6RK

Believe he mentioned a problem that they could go "hydroscopic" in
Australia?

Then he lives in Adelaide - same weather as Vancouver, RAIN!

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca