Hi all. I'm pondering how to make a 1:1 current-mode balun that will
cover a little over 8 octaves. Thankfully, I can guarantee pretty
close to a 50 ohm load over that range...20MHz to 6GHz. I have some
nice tiny coax to use in making it. To get to the low end, something
like 250nH or perhaps even a little less should do OK, but I need to
avoid resonances that will mess up the high end. An air-core solenoid
coil of about 250nH will have a self-resonance below 1GHz, so that's
probably out. Ferrite beads or binocular cores, perhaps? Anyone have
practical experience with how they behave in the GHz region?
Comments?

Cheers,
Tom