Ferrite cored balun winding. Spaced or close wound?
Im have made a 9 to 1 FT240-31 cored balun. I have read that they are less "noisy" if space wound, yet the two commercial ones I have seen are close wound. Does it matter and which is better / correct please?
Mine is in the black box, the commercial one is in the grey box. Thanks
what I can see from your photos that you have built a rf transformer, not a balun. 9:1 balun is wound in totally different way, and in that case, it matters, how you place windings. In your case, it does not matters.
Hmmm, the device I plagiarised is advertised as a balun. To be honest i had some doubt as to this, hence me not gluing the thing down. i have just bought a good book, (well, good to me, it makes fairly easy reading for a novice, and goes into some depth without arcane maths cited all the time) on antennas and has a detailed balun section, so will check it out. It's no big deal to wind something else on the core, or make another, I have several empty boxes and three more cores. Thanks for that.
To be short - balun considers wires as transmission lines, and all transformation is done by connecting them in series or parralel. Balun does not uses core magnetic capabilities for impedance transformation, these capabilities just help construction to fight with un-balancing currents.
Check this pic. Does not needs much explanation: