ken scharf ) writes:
Pete KE9OA wrote:
The only mechanical filters that I have seen problems with are the Japanese
units that you find in the JRC receivers. There is some sort of foam that
deteriorates over the years. I haven't seen a problem with Collins filters.
I have an old Collins filter made for the R390 series receivers. It is
a cylindrical filter with two pins at each end for connections. I can
hear something rattling around inside this filter as I tilt it from side
to side. Has something deteriorated inside this filter or is this
normal? A later rectangular Collins filter does NOT make this noise.

I don't think a noise is normal.

But, it's always possible that they can be dropped.

The issue Pete is talking about is that those Japanese filters were
made with different materials, and they decay with time.

Michael VE2BVW