Abstract A ferrite FM tuning core and a method of producing it. The ferrite tuning core is physically and electrically interchangeable with a powdered iron FM tuning core but exhibits a substantially lower temperature coefficient of permeability. The tuning core is a nickel-zinc ferrite containing, in mol percent, 65-70% ferric oxide, 25-30% nickel oxide, and 4.5-5.5% zinc oxide. In the method, the oxides forming the ferrite are pressed into a solid cylindrical body, and the body is heated at a rate of about 5°-15°F per minute to a maximum temperature of about 2000°-2100°F. Upon reaching the maximum temperature the ferrite body is immediately allowed to cool at a rate of about 1.5°-2.0°F per minute to a temperature below about 400°F.
A method of producing a nickel-zinc ferrite FM tuning core which is electronically and physically interchangeable with a powdered iron FM tuning core yet which has a substantially lower temperature coefficient of permeability than the powdered iron core, it being less than approximately 0.00364% per degree Fahrenheit over the temperature range between -36°F and +186°F, said method comprising the steps of: blending together 65-70 mol percent ferric oxide, 25-30 mol percent nickel oxide, and 4.5-5.5 mol percent zinc oxide to form a mixture; compressing said mixture at a pressure between 10,000-20,000 psi into a solid, elongated body; heating said body at a rate of 5°-15°F per minute over a time period of 3-5 hours to a maximum temperature of about 2000°-2100°F; immediately stopping any further heating upon reaching said maximum temperature; slowly cooling said body at a rate of about 1.5°-2.0°F per minute to a temperature below about 400°F, and further cooling said body in room air to ambient temperature.
Claim 2
Independent Claim
160 words
A method of producing a nickel-zinc ferrite FM tuning core which is electronically and physically interchangeable with a powdered iron FM tuning core yet which has a substantially lower temperature coefficient of permeability than the powdered iron core, it being less than approximately 0.00364% per degree Fahrenheit over the temperature range between -36°F and +186°F, said method comprising the steps of: blending together 65-70 mol percent ferric oxide, 25-30 mol percent nickel oxide, and 4.5-5.5 mol percent zinc oxide to form a mixture; compressing said mixture at a pressure between 10,000-20,000 psi into a solid, elongated body; heating said body at a rate of 5°-15°F per minute over a time period of 3-5 hours to a maximum temperature of about 2000°-2100°F; immediately stopping any further heating upon reaching said maximum temperature; slowly cooling said body at a rate of about 1.5°-2.0°F per minute to a temperature below about 400°F, and further cooling said body in room air to ambient temperature.