[R-390] Clevite Filters WAS: R-390 IF in 390A

[John Kolb]

On Tue, 25 Nov 2003, Dennis L. Wade wrote:

> A related question comes to mind.  Most of us have
> heard about the Clevite ceramic filters that one
> contractor (I forget who) tried to use in a run of
> 390A IF decks.  These were subsequently removed and
> the proper mechanical filters installed.
>
> I remember looking at the bandpass curve of a typical
> ceramic filter and noticing it was much smoother over
> the top (less ringing?) and much gentler skirts than a
> mechanical filter.

I don't have any experience with the Clevite ceramic filters,
but have plotted curves of the R-390A mechanical filters
and a number of ceramic filters - plots available at
<http://members.cts.com/king/j/jlkolb/site/mfcurves.htm>

The ceramic filters are indeed smoother, although very
rounded and thus attenuate high freqs more - easily corrected
with the tone controls if feeding the 390 audio output through
an external amp.

John