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The following is applicable to any soft ferrite material with a relative permeability in the vicinity of 5000, such as Amidon type J and Fair-Rite type 75:
The only RF application these materials have is as attenuators. To make high-Q coils with these materials, the maximum frequency is about 100 kHz. At 1.6 MHz, the formulas cited by Krimes are not applicable. At 1.6 MHz, the relative permeability reduces from about 5000 to about 1000, causing the inductance to be reduced by a factor of about 5. Also, the cores absorb a lot of energy at 1.6 MHz, causing the Q to be low, giving a high resistive component to the input impedance of the coil. This resistive component adds to the loss resistances of the transmitter and antenna system, causing efficiency to be reduced.
The only application high-permeability soft ferrites have to frequencies in the vicinity of 1.6 MHz is in filters, such as with “prayer beads,” the ferrite beads that RF designers spread around their circuits in the hope of reducing noise or instability. The function of the Prayer Beads is to absorb RF energy.
Type J material is clearly misapplied for an inductor in the ground lead. A core material with much lower permeability is needed, which would require more turns. More turns would increase the capacitance of the winding, causing more complexity in the design. Designing with ferrites is very difficult. Once you get the design right, the design often doesn’t work when using the same part from the same manufacturer, but with ferrite from a different batch.