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Steve,

The broad scope of this listing is commendable and useful.? However, I have noticed many times it is difficult to determine what kind of loop the poster is talking about, which can lead to confusion or misunderstanding.? The list below provides many of the basic classifications of loop antennas – there may be others.? A well-conceived topic or thread title would certainly help, or just stepping back and trying to perceive how one’s posting might be interpreted by the readers before clicking on the send button.

Just at thought,

Dexter

·???????? Receiving or Transmitting – Despite their inherent low radiation resistance, loop antennas are sometimes adapted to transmitting.

·???????? Electrically Small or Large – For electrically small loops, the dimensions of the primary coil are much shorter than the wavelength being tuned, defined as less than or equal to l/10, where l is the wavelength of the incoming signal.

·???????? Resonant or Non-resonant – Resonant loops consist of a coil and variable capacitor which resonate over a band of frequencies to produce an alternating magnetic field having a high figure of merit or Q.

·???????? Passive or Active – For passive loops, there is no active amplification outside the receiver.

·???????? Air Core or Ferrite Core – For air core, the space between turns of the coil, notwithstanding any wire insulation, is air.? It relies on the number and the area of turns for its effective height, or ability to generate a voltage across its terminals.? This differs from a ferrite core coil, which due to its high magnetic permeability can focus or concentrate a larger area of magnetic field through the center of the coil, thus greatly minimizing the size of the coil.

·???????? Spiral or Solenoid – A spiral loop is sometimes referred to as a flat or ‘pancake’ loop; that is, the coil is wound in a single plane.? It differs from a solenoid loop which is wound cylindrically along the coil’s center axis; that is, a solenoid is three dimensional.

·???????? Local or Remote – A local loop antenna is intended to operate near the radio.? Some experimenters have used variable capacitance diodes, or, as they are variously known as a varicap diodes, varactor diodes, variable reactance diodes or tuning diodes.? These devices permit a remote resonant antenna to be tuned.

·???????? Transformer-Coupled or Directly-Coupled – For a transformer-coupled loop, there are two coils, which operate on the principle of a transformer.? The primary coil is the main receiving antenna, which, in resonance with the variable capacitor, produces an alternating magnetic field.? The secondary coil, which is shielded to normalize directional response, operates by mutual inductance, and, along with a transmission line, provides low-impedance input to the radio.? A directly-coupled loop can be connected directly between the antenna input and ground of the receiver and generally operates as a low-impedance input.