On Fri, 23 Jul 2010 11:53:33 -0700, Brett Howard wrote: >Interesting enough his high power one uses two cores and appears to be >made the same as the "budget" one that is wound on one core... Seems >like stacking them on top of one another is going to just couple them >and hinder your isolation but maybe I'm wrong there....
No, the only coupling between chokes wound on different ferrite cores that provide a complete path for current (like a toroid) is the stray capacitance that results from their physical proximity. Virtually ALL of the flux stays in the ferrite core -- there is virtually NO leakage flux (that is, coupling between coils wound on different toroids). This is generally true of ALL coils wound on closed ferrite paths. Leakage flux (and thus coupling outside the core) occurs when the ferrite does NOT complete the path (for example, a coil wound on a ferrite bar, also known as a loopstick receiving antenna). If you want a very good 4:1 impedance tranforming balun for less than about 500 watts, consider building one from two of the 12-turn or 14- turn THHN chokes shown in my tutorial. Each choke is wound on a #31 2.4-inch o.d. core. Total cost about $20 (two cores plus some wire and connectors). 73, Jim Brown K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
