Lodestone Pacific engineering kits offer a wide selection of shielded coil form styles, sizes and materials suitable for applications from 200 Khz to 200 Mhz. Each kit is $50 and will be replenished free of charge upon request, forever.

Engineering Kit #3 includes samples of each configuration of tunable shield coils in materials suitable for applications from 200 Khz to 10 Mhz. Engineering Kit #4 includes samples of each configuration of tunable shielded coil form in materials suitable for applications from 1 Mhz to 200 Mhz.


The drive slots in iron powder and ferrite cores can be broken when tuned with a poor fitting tool. Tuning Tool A has a hard ceramic tip and is designed to fit Lodestone Pacific iron powder cores. Tuning Tool A is sold separately.


The quality and characteristics of the magnetic field generated in a variable inductor is determined by the quality and shape of the magnetic core materials, and by the characteristics of the winding.

A cylindrical core in the center of a spring wound wire coil form will create a magnetic field with invisible lines of flux represented by Figure 1. The construction of the Shielded Coil Form traps and channels the lines of flux within a magnetic path way increasing the efficiency and performance of the assembly as represented by Figure 2.

Figure 1

Figure 2

The more complete the magnetic pathway along the magnetic lines of flux, the higher the inductance and the quality (Q) of the assembly. The optimum state for a tuned inductor is to have the desired inductance reached when the tuning core fills the gap in the assembly and closes the magnetic field.

The Inductance of the Assembly: The inductance (L) is listed in ph (micro-henries) for 100 turns on the data sheets for each Shielded Coil Form (SCF) assembly. The number of turns of wire required for a desired inductance can be calculated from the following formula.

The inductance of the assembly is relatively flat with increasing frequency until after the peak of that assembly's Q. Above the peak Q frequency, apparent inductance will climb with frequency until the frequency when self resonance occurs. The inductances shown in this catalog are measured at frequencies below the Q curve's peak frequency.



4679 Wesley Drive * Anaheim, California 92807 U.S.A.
Phone (714) 970-0900
* FAX (714) 970-0800


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