"Michael Black" wrote in message
...

Well there were other manufacturers who made mechanical filters in
the sixties. You'd see them in the Lafayette catalog, and mentioned
in reviews (though I've always wondered if some of those reviews got
it wrong, and they weren't mechanical filters). But they were never
commmon. They were cheaper than Collins filters, but I have no idea how
absolutely cheap they were for the time. I don't recall coming across
real specs in the old magazines, either. I also recall in recent years
that it was those other filters that used foam rubber inside, and by
now much of that has deteriorated.

Michael VE2BVW


I had that happen with the filters in my NRD-515 JRC receiver.
Fortunately, it wasn't too difficult to open the filters up, which
allowed me to dissolve the old foam rubber
blanket that cushioned the mechanical filter elements. The
foam had to decayed to a chewing gum consistency and the
filter losses skyrocked. These were late 70s or early 80s
vintage IIRC. Regarding the patent issues, I don't recall
the particulars.

Pete k1zjh