A couple rules for toroidal inductors might be useful. To increase the
reactance you increase the number of turns -- the inductance goes up
approximately the square of the number of turns. To increase the power handling
capability you add additional cores to make a stack of cores. This will also
help with the inductance since the toroid core AL value is affected by the
cross sectional area of the core.
I would expect that stacking cores might be the more economic route to the
desired result.
If you are simply building a an RF choke to prevent feed line common mode RF
current you should be using Type 31 material. For really good RF choking at 1.8
MHz you should plan on about six turns through at least five stacked cores of
type 31 ferrite 2.4 inches
o.d. [60 mm] Such a choke will have about 5000 ohms of impedance, mostly
resistive. It will certainly handle 1.5 KW going through the feed line [ if
the feed line can handle the power]. See K9CY's online paper discussing such
RF chokes. You may also want to check my web site for some measurements of
various RF chokes made with type 31 using different numbers of cores and turns.
Tod, K0TO
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