[ARC5] BC-455 IFT - photo attached

[Ian Wilson]

The untuned winding will have fairly hefty self-capacitance (recall that
it's a little over 2mH, and is not split into smaller units in the way that
RFCs often are).

I would be surprised if adding 20pF across the untuned winding had
much effect on the primary (but I have been wrong/surprised before).

73, ian K3IMW

On Wed, Oct 29, 2014 at 2:33 PM, Dennis Monticelli <
dennis.monticelli at gmail.com> wrote:

> Ken,
>
> The pic is very helpful.
>
> The pie coil is not a toroid. It's wound axially not radially.  So it will
> indeed couple to the single layer but not very well.  If there was a
> iron-powder core running through the form, it would couple much better.
>
> One way to determine the degree to which the tuning on one side would
> interact with the tuning on the other side is simply to solder a fixed
> capacitor across the untuned side of this loosely coupled transformer you
> pulled from the radio and then re-dip the assembly to see how far it moved
> off resonance.  Try soldering about 20pF across the untuned coil to find
> out how many kHz it moves.  Electrode plus wiring capacitance is probably
> closer to a 10pF load, but a larger cap makes it easier to measure the
> delta.
>
> Dennis AE6C
>
>
>
> On Wed, Oct 29, 2014 at 1:19 PM, Kenneth G. Gordon <
> kgordon2006 at frontier.com
> > wrote:
>
> > OK. Here is a photo of the IFT with the cover removed. It probably won't
> > show up on the forum, but Dennis will see it, and if anyone else would
> > like to see it, let me know.
> >
> > There is about a 3/16" space between the pie-wound coil and the single-
> > layer coil, both wound on the same form. As I said, it looks pretty loose
> > to me. In addition, that pie-wound coil looks like a toroid to me,
> > although it isn't wound on a toroid core. Even so, I would think that
> > coupling to that form of coil would be somewhat problematic.
> >
> > I agree with Mike: a high-impedance broad-band input to the grid, AKA RF
> > choke. :-)
> >
> > Ken W7EKB
> >
> >
> >
> >
> > -------------- Enclosure number 1 ----------------
> >  * This message contains the file 'IFT7277.jpg', which has been
> >  * uuencoded. If you are using Pegasus Mail, then you can use
> >  * the browser's eXtract function to lift the original contents
> >  * out to a file, otherwise you will have to extract the message
> >  * and uudecode it manually.
> >
> >
> ______________________________________________________________
> ARC5 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/arc5
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:ARC5 at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>