We have tested a different option and found that two huge chinese MnZn cores (search for "Cores Green 75mm x 39mm x 13mm") stacked on top of each other and afterwards wound in a similar fashion (not in the number of turns, but in terms of covering the core with windings, style of twisted wire and connection) to the Bode 100 transformer gives the attatched result. Seems like a lot of wideband transformer for about 10€ for the cores. The much increased volume of core material might also help with saturation?

Hi,

Can you post a schematic showing how this transformer was measured?

If I calculate the inductance:

for one core:

Area = Thickness x (D - d)/2

Where

D= outside diameter = 75mm

d= inside diameter = 39mm

Thickness = 13mm

Area = 13 x (75-39) /2 = 234E-6 m

^{2}Mean magnetic Path length

Pi x (D + d)/2 = PI x (75 +39) /2 = 180E-3

Assume that this core is a power grade of ferrite with a relative permeability of 2000.

AL= mu

_{0} x mu

_{r} x Area/length

AL = 4E-7 x Pi x 2000 x 234E-6 / 180E-3

= 3.28uH per turn

^{2}Assume 50 turns

Lmag = 50

^{2} x 3.3uH

= 8mH

and two cores stacked would be 16mH

**50 Ohm test circuit**[attachimg=1]

The LF -3dB for this configuration is calculated

R1 // R2 = R

LF(-3db) = 1/(2 x Pi x L/R)

**= 250 Hz**

It just seems too good …

Regards,

Jay_Diddy_B