Topband: core inductance and current - some measurements.

[Tom Rauch]

> The indicated inductances with just *3-1/3 turns* on the 73 mix Binocular
> core were:
> 0 ma    90.04 uhy
> 15 ma 90.04 uhy
> 29 ma 89.71 uhy
> 58 ma 97.11 uhy
> 110 ma 75.41 uhy

Since just one bit of error in the A/D conversion of the 259 can cause
similar variations as Charlie sees between 0mA and 58mA, the actual change
might be significantly less.

The 110mA 75uH change certainly looks like the real start of the inductance
slope from steady dc bias.

My tests were with a dc bias for a short period and then removal of all bias
and a re measurement of impedance. I took some shots of the display, and
when I get time I'll post them for viewing. They will also provide some idea
of the impedance curves of 73 cores between 300kHz and 200MHz, since I swept
them using a Smith Chart screen for display.

I've received three e-mails from people who have received incorrect mix
cores from a popular core retailer. I didn't realize this was a common
problem, but it looks like 43 mix and 73 mix cores are mixed on occasion!!

73 Tom