On 1/8/2018 8:19 PM, K9MA wrote:
I would be cautious about using a transformer above 40 meters, as the stray capacitance may be too large. I haven't tried it, though, so it might work with some transformers.
For years, we've been winding our transformers wrong. The windings should be on opposite sides of the core, so that capacitive coupling is minimized, NOT laying on top of one another. In a ferrite materialthat is SUITABLE for use as a transformer, the mu is high enough that a VERY high fraction of the flux in toroid is contained within the core, with very little leakage flux. Windings that lay on top of each other maximize capacitive coupling, and thus maximize common mode current. Windings on opposite sides of the core minimize common mode current.
Ferrites are semiconductors, so they act as a dielectric. When we place windings on opposite sides of a core, we maximize magnetic coupling and minimize capacitive coupling, which is from one winding to the core and from the core to the other winding. That capacitance is VERY small if the windings are widely spaced.
73, Jim 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 Message delivered to arch...@mail-archive.com
