[ARC5] BC-455 IFT - measurements

[AKLDGUY .]

This is a confusing thread to follow because some are talking of a dual
winding, others of a single winding. If there's a single winding with an
inductance that seems too high to some, perhaps the following will help.

The single winding is not merely coupled choke-fashion to the grid via
a coupling capacitor. It resonates with that coupling capacitor (which
some are saying is 180pF) in series with the grid input capacitance Ci
plus stray capacitance Cs. Let's refer to Ci + Cs as Cis.

Do your series capacitor calculation. 180 x Cis / 180 + Cis will result in a
capacitance of a bit *less* than Cis since 180 is bigger than Cis. Now do
your resonance calculation. It may come out to about 2830 KHz.

Capacitors in series are like resistors in parallel.
The result is a capacitance lower than the lowest.

The grid is picked off at the junction of the 180 and Cis, which is the
capacitance version of a tapping on the coil.

73 de Neil ZL1ANM