>Rich:
>
>Probably the chokes you refer to in your 1990 article were not available at
>that time. However, let me quote from a 1996 ARRL Handbook, page 19.17.
>
not a good bet.
>"Type 72, 73 or 77 ferrite gives the greatest impedance over the HF range.
>Type 43 ferrite has lower loss, but somewhat less impedance. Core
>saturation is not a problem with these ferrites at HF; since they overheat
>due to loss at flux levels well below saturation. The loss occurs because
>there is insufficient inductive reactance at lower frequencies. Eight to
>ten turns on a toroidal core or 10 to 15 turns on a rod are typical for the
>HF range. Winding impedance increases approximately as the square of the
>number of turns." See Gerry Sevicks work and books -- probably in a
>library near you.
>
>After the 77 material ferrite4 was developed, through cooperation with
>Gerry Sevick and Amidon, thef FT-240-K ferrite core was introduced. It is
>a superior core and can be used very effectively for 1:1 or 4:1 baluns --
>peferred type is the Guanella current design over the better known
>Rhuthroff voltage design. Fifteen turns on two stacked FT-240-K will easily
>reach 146 uhy at 3.5 MHz (measured). The baluns themselves can use only 8
>to 9 bifilar turns and be extremely effective over the entire HF band.
>
>Your coaxial balun could be better replaced with a coaxial bead balun using
>the popular FB-73-2401 beads by Amidon.
>
The air core ugly balun would not saturate with 14k. . Ferrite cores
saturate.
......
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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