[ARC5] BC-455 IFT - photo attached

[Ian Wilson]

My measurements were made at around 100kHz.

73, ian K3IMW


On Wed, Oct 29, 2014 at 2:48 PM, Dennis Monticelli <
dennis.monticelli at gmail.com> wrote:

> No doubt there is significant winding capacitance but I don't think that
> will affect the coupling coefficient we are trying to evaluate.
>
> Besides the measurement of the net inductance at 2830 was inclusive of the
> winding capacitance.  If fact, there was no way to separate it with simple
> measurement techniques.
>
> Dennis AE6C
>
> On Wed, Oct 29, 2014 at 2:39 PM, Ian Wilson <ianmwilson73 at gmail.com>
> wrote:
>
>> 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
>>> >
>>> >
>>> >
>>> >
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>>
>>
>