K7ITM wrote in news:42d7e9e9-f39b-4610-b6ad-
:

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

Tom,

We from time to time come across applications where an RF choke is
required to be effective over such a wide range. For example, an injector
to supply DC on a coax line to an LNB. Perhaps some of the techniques for
cascading chokes to extend the frequency range might offer a solution.

I have been playing around with some 1:1 choke balun designs for HF, and
one that I tried used a pair of suppression sleeves to synthesise a
binocular, see http://www.vk1od.net/balun/G1-1-LF1260/index.htm . The
thing that I discovered is that self capacitance is an issue, though I
could fit four turns on the cores, the self resonance was quite low (well
below 10MHz IIRC). In the case of 3 turns, self resonance around 12MHz
isn't a problem.

If I were to try to extend the upper range of this balun, I would try
passing the coax exiting the pair of cores through another core (1t),
possibly of a lower µ material, possibly a cascade of cores of
successively lower µ material.

Owen