On 12/28/2010 09:32, wa2mze posted:
I have several dozen multi-aperture cores that appear to be type BN-43-202's as they are shiny black/gray in color and about the same size. Winding 23 turns of wire on the core and measuring the inductance (with a digital L/C meter) gives about 2050uh, (2.05mh) which doesn't match the AL factor for #43 material, or #73 or #61 either. It's about twice the inductance that I should get (with the on line calculator) for #43 and a third that expected with #73. I wonder what this mystery material is, and what it would be good for.
My guess is that it should work as well as #43, at least below 20mhz and require fewer turns.

What inductance SHOULD a broadband transformer have on it's primary and secondary windings (assume impedances between 50 and a few hundred ohms matching) for use on the HF bands?