I am not sure how hard they would be to make. I've got an old article that
Mr. Johnson of Rockwell Filter Products forwarded to one of the engineers at
Rockwell-Collins. There was a note included with the document saying "after
you read this, you will be an expert on Mechanical Filters". I have to dig
that up one of these days.
I remember the Motorola Permakay filter units that were in the Mocom 70
radios. I dismantled one the filter assemblies one day and found 14
individual ceramic filter elements, with an amplifier embedded in the
bundle. They were pretty decent units.
There were some pretty cool articles in those old magazines. I remember an
old in Ham Radio........the project was kind of a spectrum analyzer for the
FM broadcast band using a Bragg Cell Detector. After seeing that article, I
became a homebrewer.

Pete

"Michael Black" wrote in message
...

"Pete KE9OA" ) writes:
Those filters were pretty awful................I don't remember the name
of
the company name, but it started with the letter K.
They were used in the NRD-515 and in the Yaesu FRDX-400. They were filled
with some sort of foam substance that turns to a sticky jelly after many
years, causing the insertion loss of the filter to degrade. Peter Bertini
had an article in Popular Communications a few years ago on how to repair
them. I did just that for a friend's FRDX-400. You have to dismantle the
filter and clean out all of the goo with alcohol..........I used a
product
called Flux-Off.

Of course, one pays quite a bit for Collins mechanical filters, and
that's always been the case. Those Japanese mechanical filters were
significantly cheaper, at least back then. Reading the old magazines,
I've sometimes wondered if at least some times people were calling
ceramic filters the wrong thing.

Your description of the insides reminds me that some guy wrote about
a homebrew receiver in the early sixties, I think it was in CQ, and
he made his own mechanical filter. No, I don't have it handy and
can't specify the issue, but every so often I come across the article,
and wonder how practical it was to do. It seems like we'd have
read more about doing it if it was something easily doable.

Michael