The Loop in Ground project is about a receive only antenna for low HF, but usable from MF to HF. The objective is an antenna of that is small, low profile, and can be located outside the zone where evanescent modes dominate around noise current carrying conductors, like house wiring to minimise noise pickup.
To some extent, the project was inspired by KK5JY's Loop on Ground (LoG).
This article presents measurements and the three terminal equivalent impedance model.
Above is the three terminal equivalent impedance model. Elements Z1, Z2 and Z3 are derived from measurements Za, Zb, and ZC as discussed at Find three terminal equivalent circuit for an antenna system.
A NanoVNA was calibrated for a fixture designed for such measurements, and a scan from 1-30MHz for each of Za, Zb, and ZC was captured and saved to the SD card.
Above is the measurement of ZC, the common mode impedance Zcm which is of interest as it informs strategies for minimising injection of common mode feed line current into the coax interior.
Whilst a small loop in air tends to have a very high common mode impedance, the lig is quite the opposite.
Above is a plot of the Za and Zb measurements. Though the wire geometry is quite symmetric, the electrical symmetry is not perfect, probably due to less than uniform soil characteristic over the antenna site.
Above is a calculation of the various elements at 3.61MHz.
A work in progress…