Ex: when it is 1/2 wavelength long it isa Have you looked at your antenna impedance? Unless it is a terminatedĪntenna such as a Beverage the feedpoint Z is going to vary all over the On Sun, at 10:11 PM rickstealey via Groups.Io wrote: For bilaterally wound common modechokesĪt HF, the red powdered iron core (µ of 10) is best, but start with the 'balun' forms an inductive (reflective) choke for common mode currents on Have a very large µ and loss within the ferrite material. Even ferrites aimed at reducing EMC will work fine as they Multiple times (as many as you can get without overlapping) through the This configuration should consist of winding coaxial cable 'balun', I'd use a ferrite with high permeability (43, 75, 71, or 35 I presume your are using coaxial cable? To make a choke (current) Of work, both theoretical and experimental, to support his arguments. simple paired windings of #12 THHN actually worksīetter due to shorter lengths and lower interwinding capacitance.ĭon't take my word for it, I'm only the messenger. He doesn't even recommend coax for theĬhokes any more. Out, a poorly chosen combination can actually act a series tuned circuitĪnd totally defeat its purpose. Isn't necessarily a good idea because you're trying to optimize theĬombination of the interwinding capacitance and the coil inductance toĬreate a tuned circuit for the range of interest. Primarily because it has considerable internal loss and the otherĪlso, the number of turns is fairly important. Much the only really good material for a common mode choke at HF. Zillion times on the TowerTalk reflector, type 31 material is pretty That's not really a very good suggestion. This is off topic forthe NANOVNA site and, likely, should be taken Recommendations to many hours of winding and measuring with the HP 8753C. Bifilar wound common modeĬhokes are a whole different ball of wax. Material are great for these applications. Per turn and, consequently, offer more choking capability. For current baluns, the high µ materials yield more L I rest my recommendations on measuring many using the HP 8753C vector Subject: Re: How to find the right ferrite toroid for a receiving antenna balun?
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