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February 28th 11, 12:05 AM posted to rec.radio.amateur.homebrew

Bill M[_5_] Bill M[_5_] is offline

Bill M[_5_] is offline

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Kokusai filter

wrote:
On 27 Feb,
Bill M wrote:

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 had one in my KW2000A. It lost sensitivity and drive due to filter
degrading. I unsoldered the can and removed the goo that the foam had become,
much improving performance but it's still well below par. The transducers or
transformers at the ends of the filter are easily damaged and also likely to
fail. Somewhere on the internet are details for refurb. There was also an
article years ago on upgrading to a crystal filter but I can no longer find
it. I've now given up on that rig and gone to an SDR one.

Thanks Brian. I was afraid of that. I never had the radio up to 100%
originally. It was a homebrew and I guess its like a new project
nowadays with all the pieces there to troubleshoot. Its not a
'necessary' rig but I'd sure like to get it in shape for old times
sake...if I can. It was a learning experience before - some things
don't change, do they?

Regards,
Bill

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