[hpsdr] PennyWhistle T1 construction and measurement

[Andrew Howell]

After sitting on my workbench for far too long, I finally decided to 
assemble my PennyWhistle.

I have some very basic questions about T1 construction. I made the 
bifilar secondary and connected it up as shown in the diagram in the 
instructions.

The instructions say is should be 50 ohms impedance on the primary, 50 
ohms on across the secondary, and 25 ohms impedance on between the 
secondary leads and the center-tap.

I have an LCR meter, but I don't think that is going to help me, as it 
measures Z at a max of 10khz.

I do measure 12.9 uH on the primary, and 12.8 uH on the secondary. The 
two sides of the secondary to center-tap are each 4.6 uH.  Those two 
secondary to center-tap inductances seem low. I would have expected 
6.4uH, ie half the 12.8uH of the secondary.

So, are these the values I should expect? Why don't the secondary to 
center-tap inductances add up to the inductance of the whole secondary 
leads?

I expect I'm about to learn something :)

73, Andy - KF5JLJ