[R-390] A 6kc. mechanical filter for a R-390a?

[Alan Victor]

First you need to establish the current terminating Z for the mechanical
filters in the 390A. Then you need to know the required termination Z for
the ones you wish to install. Designing a matching system to handle this
problem is pretty straight forward. I do not believe the current 390A
mechanical filters are that high a Z. At least the ones I have worked with
at 455 kHz and built some receivers around were only about 3k//?? Cpf. I
would have to look them up in my notes.

Alan W4AMV

On Wed, Jun 14, 2017 at 7:41 PM, Al S. <racalra17 at gmail.com> wrote:

> I seem to recall an article somewhere?, maybe the Y2k manual or notes by
> Mr. Dallas Lankford on using the modern Collins torsional filters as
> roofing filters in the receiver. Using toroidal matching transformers.
>
> Al
> On Jun 14, 2017 10:04 PM, "Bob kb8tq" <kb8tq at n1k.org> wrote:
>
> > HI
> >
> > You will have to use some sort of transformer match. Doing really wide
> > range
> > impedance matching with networks is a pain. You probably are going from
> > megohms
> > to hundreds of ohms …
> >
> > Bob
> >
> > > On Jun 14, 2017, at 8:57 PM, Al S. <racalra17 at gmail.com> wrote:
> > >
> > > I have one of the more modern blue cased Collins mechanical filters
> here.
> > > It was apparently used in the Racal 6790 receiver BW is 6.0 kc. 526
> 9957
> > > 040.
> > >
> > > This filter is designed to be used in that SS receiver and for lower
> > > impedance, than the higher impedance the stock 390a filters see.
> > >
> > > I would like to experiment with this filter in a 390a. Any ideas on
> > > toroidal matching to the IF deck in the 390a.
> > >
> > > Thanks
> > >
> > > Al VE3AJM
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