I would like to add a balun/choke to my dipole for the reasons outlined in Using a balun with a resonant dipole. In the spirit of continued kit and/or DIY building for my ham shack, I set out to investigate how I might best proceed "from scratch".
Simply wind two conductors together over some sort of core?
At http://vk6ysf.com/balun_guanella_current_1-1.htm a design is given for a 1:1 current balun that simply wraps a pair of wires around a toroidal core:
…or as http://vk5ajl.com/projects/baluns.php#current even shows:
I suppose the air-wound "ugly balun" as demonstrated at http://www.hamuniverse.com/balun.html also fits in this same category, unless using coax in place of the bifilar winding somehow changes things?
So that's all well and good, I guess.
Two tangled toroids?
But then — under the same "Guanella balun" name as the first diagram above, no less! — I find that http://www.kn9b.us/guanella-balun presents this diagram:
…which is to be built using two toroids resulting in something that looks like this:
Is there any benefit to this dual core balun over the single core type? What is the purpose of this sort of "push-pull" reminiscent design? Is it worth buying two toroids and going to twice the trouble of winding and sorting out which loose ends connect to which others, versus just winding a pair of wires around a rusty bolt, or wrapping some coax around some scrap PVC?