Uploaded December 2023 | Updated September 2026, 2 weeks ago
The plastic pipes I have used to make coils have never been a problem, UNTIL NOW! By (bad) luck I ran into a type of plastic pipe that does NOT work for a crystal radio coil. It seems to have a filler that interacts with radio waves lowering the inductance of the coil to 1/3rd the calculated/expected value (don't know what other ill effects it might have.)
Crystal Radio Coil Sizing: youtu.be/ejHk5tFeKHk
Calculator: m0ukd.com/calculators/air-cored-inductor-calculator
UPDATE: The most common fillers used in plastic include
Calcium carbonate (CaCO3) Magnetic susceptibility (χ) −3.82×10−5 cm3/mol
Talcum Mg 3Si 4O 10(OH)2
Barium sulfate Magnetic susceptibility (χ) −71.3·10−6 cm3/mol
Wollastonite CaSiO3
Magnetite Fe2+Fe3+2O4 Ur = 5.0 Magnetic
From ChatGPT (for what it's worth).
ME:
plastics now contain a lot of fillers such as Calcium carbonate, Talcum, Barium sulfate, Wollastonite, Magnetite, etc. given the relative permeability of these, how do they affect the use of plastics with this fillers as RF cores. Engineering level answer please.
ChatGPT Answer:
The use of fillers such as calcium carbonate, talcum, barium sulfate, wollastonite, magnetite, etc., in plastics can significantly impact their electromagnetic properties, especially when used as RF (Radio Frequency) cores. The relative permeability of these fillers plays a crucial role in determining the effectiveness of the plastic composite as an RF core. Here's how different fillers can affect the performance:
Calcium Carbonate (CaCO3):
Impact on Permeability: Generally, calcium carbonate has a relatively low permeability compared to some other fillers. This can influence the overall permeability of the composite material.
Effects on Dielectric Properties: Calcium carbonate is known for its dielectric properties, which can affect the electrical performance of the material. It may contribute to changes in the dielectric constant and loss tangent.
Talcum:
Impact on Permeability: Talcum has a low permeability, and its use in plastics can contribute to enhancing the magnetic properties of the composite material.
Dielectric Properties: Talcum may also influence the dielectric properties of the material, affecting factors such as the dielectric constant and loss tangent.
Barium Sulfate (BaSO4):
Impact on Permeability: Barium sulfate has high density and can significantly affect the permeability of the composite material, making it more suitable for certain RF applications.
Dielectric Properties: Barium sulfate is generally considered a good dielectric material, and its use may contribute to maintaining stable electrical properties.
Wollastonite:
Impact on Permeability: Wollastonite has a low permeability, making it a potential candidate for enhancing the magnetic properties of the plastic composite.
Dielectric Properties: Wollastonite can influence the dielectric properties of the material, and its use may contribute to changes in the dielectric constant and loss tangent.
Magnetite:
Impact on Permeability: Magnetite is a magnetic material with high permeability, making it a suitable choice for applications where magnetic properties are crucial, such as RF cores.
Dielectric Properties: Magnetite can affect the dielectric properties, and its use may contribute to changes in the material's electrical characteristics.
In engineering terms, the choice of filler depends on the specific requirements of the RF application. Designers need to carefully consider the trade-offs between permeability, dielectric properties, mechanical strength, and other factors to optimize the performance of the plastic composite as an RF core. Additionally, the concentration and dispersion of fillers within the plastic matrix are critical parameters that can influence the overall electromagnetic behavior of the material. Experimental characterization and testing are often necessary to fine-tune the formulation for a particular RF application.
The plastic pipes I have used to make coils have never been a problem, UNTIL NOW! By (bad) luck I ran into a type of plastic pipe that does NOT work for a crystal radio coil. It seems to have a filler that interacts with radio waves lowering the inductance of the coil to 1/3rd the calculated/expected value (don't know what other ill effects it might have.)
Crystal Radio Coil Sizing: youtu.be/ejHk5tFeKHk
Calculator: m0ukd.com/calculators/air-cored-inductor-calculator
UPDATE: The most common fillers used in plastic include
Calcium carbonate (CaCO3) Magnetic susceptibility (χ) −3.82×10−5 cm3/mol
Talcum Mg 3Si 4O 10(OH)2
Barium sulfate Magnetic susceptibility (χ) −71.3·10−6 cm3/mol
Wollastonite CaSiO3
Magnetite Fe2+Fe3+2O4 Ur = 5.0 Magnetic
From ChatGPT (for what it's worth).
ME:
plastics now contain a lot of fillers such as Calcium carbonate, Talcum, Barium sulfate, Wollastonite, Magnetite, etc. given the relative permeability of these, how do they affect the use of plastics with this fillers as RF cores. Engineering level answer please.
ChatGPT Answer:
The use of fillers such as calcium carbonate, talcum, barium sulfate, wollastonite, magnetite, etc., in plastics can significantly impact their electromagnetic properties, especially when used as RF (Radio Frequency) cores. The relative permeability of these fillers plays a crucial role in determining the effectiveness of the plastic composite as an RF core. Here's how different fillers can affect the performance:
Calcium Carbonate (CaCO3):
Impact on Permeability: Generally, calcium carbonate has a relatively low permeability compared to some other fillers. This can influence the overall permeability of the composite material.
Effects on Dielectric Properties: Calcium carbonate is known for its dielectric properties, which can affect the electrical performance of the material. It may contribute to changes in the dielectric constant and loss tangent.
Talcum:
Impact on Permeability: Talcum has a low permeability, and its use in plastics can contribute to enhancing the magnetic properties of the composite material.
Dielectric Properties: Talcum may also influence the dielectric properties of the material, affecting factors such as the dielectric constant and loss tangent.
Barium Sulfate (BaSO4):
Impact on Permeability: Barium sulfate has high density and can significantly affect the permeability of the composite material, making it more suitable for certain RF applications.
Dielectric Properties: Barium sulfate is generally considered a good dielectric material, and its use may contribute to maintaining stable electrical properties.
Wollastonite:
Impact on Permeability: Wollastonite has a low permeability, making it a potential candidate for enhancing the magnetic properties of the plastic composite.
Dielectric Properties: Wollastonite can influence the dielectric properties of the material, and its use may contribute to changes in the dielectric constant and loss tangent.
Magnetite:
Impact on Permeability: Magnetite is a magnetic material with high permeability, making it a suitable choice for applications where magnetic properties are crucial, such as RF cores.
Dielectric Properties: Magnetite can affect the dielectric properties, and its use may contribute to changes in the material's electrical characteristics.
In engineering terms, the choice of filler depends on the specific requirements of the RF application. Designers need to carefully consider the trade-offs between permeability, dielectric properties, mechanical strength, and other factors to optimize the performance of the plastic composite as an RF core. Additionally, the concentration and dispersion of fillers within the plastic matrix are critical parameters that can influence the overall electromagnetic behavior of the material. Experimental characterization and testing are often necessary to fine-tune the formulation for a particular RF application.
