On 1/20/2011 11:34 AM, Craig D. Smith wrote: > A hint for those of you who are contemplating placing an order for some of > the clamp-ons: The smaller diameter clamp-ons look attractive at first > glance due to their low prices and ability to fit most of the small cables > in your shack. But remember the choking impedance goes with the square of > the number of turns. A more expensive core with a larger aperture will be a > much better bang-for-the-buck. For example, a core that allows 3 turns of a > given cable will be 9 times more effective than a single turn core and might > only cost only 50% more. Needing to use several single turn cores adds up > quickly cost-wise.
Good advice. -- but there's more. RFI suppression comes from a high resistive impedance, which in turn occurs around the resonance of the choke. A single pass through a typical #31 or #43 core is resonant around 200 MHz -- USELESS on HF. Multiple turns moves the resonance of the choke lower in frequency where we need it. My RFI tutorial includes graphs of MEASURED data for some useful cores, and it also includes a list of ferrite cores that are most useful on the HF and VHF bands. See Appendix One. See my previous post in this thread for a link to the tutorial. > I use lots of the 0431164181 clamp-ons here. Yes,something this size is quite useful for quieting down noisy computer and audio gear. 73, Jim Brown K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
