Anybody given this a try?
This has been puzzling me: The point of coax is to keep all the field inside the coax. But the way a toroid works is to interact with the field. Why doesn’t that prevent the balun from working when coax is used? From what I’ve been reading, is it that the balun is only affecting the current on the outside of the shield by design?
exactly, the ferrite only affects common mode current. you can think of coax as being composed of 3 conductors, core, interior of shield and exterior of shield. above some frequency and below frequency where coax starts to work like a waveguide, internal surface and core carry opposite currents (differential mode), and external surface carries common mode current. these can be treated as separate, except at the ends, because of skin effect. but also you can use twisted pair, because differential mode currents cancel out there
You have to keep in mind to not exceed coax bending radius. Solid insulator (as in not foam) coax works better. Somebody has measured them http://www.karinya.net/g3txq/chokes/
I’ve seen people using twisted pair of enameled wire (50 ohm) instead, or a pair of insulated twisted wires connected in parallel (each is 100 ohm impedance) this allows for much tighter turns. This works only for HF, for VHF and up there are alternatives and multiple turns don’t make sense, it’s better to use ferrite beads
Plenty of people have: works 😊
