
Capacitors are incredibly simple. a pair of conductive bits, separated by some dielectric media, and you just charge up that field between them until it eventually arcs if the voltage is too high. I started looking more into what material options for dielectric exist, and how changes in dielectric strength and constant. . Unfortunately while reading about capacitor dielectrics I came across a comment saying that even a small air gap between two dielectric. . The calculation that killed this path of DIY capacitors for magloops was that of power dissipation inside the dielectric material. I had seen tables of “tangent loss coefficient”, but thought that *those numbers seem small. .. . With dielectric losses understood, my choices returned to an air variable capacitor, or a vacuum variable cap. Seeing that most any size of vacuum variable cap started at $150+ on Ebay, I set out to make a simple. [pdf]
In this case, a vacuum variable capacitor is used, rated to a peak current of 57 amps and a peak voltage of 5 kilovolts. The magnetic loop design leads to antenna which is tuned to a very narrow frequency range, giving good selectivity. However, it also requires retuning quite often in order to stay on-band.
Magnetic Loop Calculator v.1.6 by KI6GD It’s a light magnetic loop antenna calculator that run on MS Windows, and allow to calculate capacitor values and voltage based on Loop circumference, conductor diameter, desired resonant frequency and the operating power.
TA2WK (old TA1LSX), 73 High Voltage Butterfly Capacitor for Loop Antennas - TA2WK (TA1LSX): Hello Everyone, Wanna build a magnetic loop antenna? Magnetic loop antenna is a compact efficient antenna that is ideal for portable operation or limited spaces and can be improvised inexpensively.
Similar to a separate coupling loop, it is optimally located opposite the gap in the loop, near the low impedance point of the loop. Traditionally, to allow a mag loop to tune below its natural self-resonant frequency, a tuning capacitor is shunted across the small gap.
The initial tests of the 40m loop were very promising. During a CW contest, the 40m loop made numerous DX contacts in Europe. When running at 500W, the capacitors showed no signs of heating (SWR drift, physical warmth, etc.). I ran several computer models of this antenna, to determine the effect of differing installation heights.
It’s a light magnetic loop antenna calculator that run on MS Windows, and allow to calculate capacitor values and voltage based on Loop circumference, conductor diameter, desired resonant frequency and the operating power. Works either in Standard and Metric units, and let you choose on material, and loop shape, as circular, square or octagon.

The energy content of current SMES systems is usually quite small. Methods to increase the energy stored in SMES often resort to large-scale storage units. As with other superconducting applications, cryogenics are a necessity. A robust mechanical structure is usually required to contain the very large Lorentz forces generated by and on the magnet coils. The dominant cost for SMES is the superconductor, followed by the cooling system and the rest of the mechanical stru. [pdf]
The magnetic field energy stored is Energy storage in magnetic fields is expensive, making technical applications impractical. For example, large liquid helium cooled superconducting magnets for magnetic resonance imaging (MRI) or high-field nuclear magnetic resonance (NMR) spectroscopy require currents of 200 A.
Superconducting magnetic energy storage (SMES) systems store energy in a magnetic field. This magnetic field is generated by a DC current traveling through a superconducting coil. In a normal wire, as electric current passes through the wire, some energy is lost as heat due to electric resistance.
Owing to the capability of characterizing spin properties and high compatibility with the energy storage field, magnetic measurements are proven to be powerful tools for contributing to the progress of energy storage.
For a magnetostatic system of currents in free space, the stored energy can be found by imagining the process of linearly turning on the currents and their generated magnetic field, arriving at a total energy of: where is the current density field and is the magnetic vector potential.
Every magnetic field contains some form of energy, which we generally refer to as Magnetic Energy, W m. With the energy stored in a magnetic field being one of the fundamental principles of physics, finding applications in various branches of science and technology, including electromagnetism and electronics.
Considering the intimate connection between spin and magnetic properties, using electron spin as a probe, magnetic measurements make it possible to analyze energy storage processes from the perspective of spin and magnetism.
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