[ARC5] BC-455 IFT - photo attached

[Dennis Monticelli]

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
>
>
>
>
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