On Sun, 27 Feb 2011, Bill M wrote:

Hi,

I recently re-found a homebrew receiver that I built back in the 80s and am
going to try to get it going again.

My question is regarding the Kokusai MF-455ZU-21H mechanical filter. This was
a popular filter in its day and I wonder how well they hold up over time? I
know some of these things had foam that melts/disintegrates into mush. Any
comments or observation on this particular type would be appreciated.

I don't know which filters had the foam problem, all I remember hearing
about is "Japanese mechanical filters".

But they have been discussed before, I think here but maybe in the
boatanchors newsgroup. I can almost picture someone detailing how to
renovate them. I just tried "mechanical filter" foam and that gets
some relevant hits, but apparently aquariums use "mechanical filters" so
there must be some word that would limit it to radio. One post had a link
to a webpage, but the webpage is no longer there, so doing a more careful
search of the mewsgroup archives and then a websearch might help.

Michael VE2BVW