Single-Turn Transmitting Loop Antennas of Various Regular Shapes over a Range of Operating FrequenciesAuthor: R.J.Edwards G4FGQ © 9th February 1998
For given perimeter, conductor diameter and height above ground this program computes the radiating efficiency and other characteristics of single-turn, transmitting loop antennas of various regular shapes over a range of operating frequencies. The program applies to antennas with loop perimeters of half-wavelength or smaller.
Assumptions: The main loop conductor is untarnished copper, the operating frequency is at least 100 kHz, and the loop is in a vertical plane spaced 1-diameter or more away from other conductors with ordinary compacted garden soil below.
There are two methods of coupling the main loop to the feeder: either via a small internal inductively-coupled loop or via a ferrite-cored transformer of suitable grade such that the main loop needs only one turn and the feeder winding has a reactance 2 or 3 times the feedline impedance. Final adjustment of the coupling loop may be made by changing its diameter or by rotating with respect to the plane of the main loop. Coupling loop or transformer should be fitted approximately opposite the tuning capacitor. The diameter of wire used for the coupling loop need be no greater than needed to make self-supporting. It is advisable to insulate the main loop from coaxial feed-line.
There is little to be gained in efficiency by increasing main loop conductor diameter when its resistance is already less than earth proximity resistance. The computed loss relative to ideal applies equally to transmitting and receiving.
Take care with measurement units when entering and reading data.
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