Active Loop AAA-1 Performance at VLF and LF

This document details the performance of the AAA-1 active loop antenna at Very Low Frequency (VLF) and Low Frequency (LF) bands. It presents measurements and suggestions for improving reception in these ranges. The document explains the AAA-1's frequency response, noting that a small loop with a low input resistance trans-impedance amplifier has a flat frequency response to electromagnetic field intensity E. It discusses the current source model of a small loop and the M factor (M=A/L) that characterizes loop performance. Measurement setups for both high frequency and VLF/LF responses are illustrated, including diagrams for simulating current and voltage sources. The document also addresses the transition from a current source model to a Thevenen equivalent circuit for low frequencies where the loop inductive impedance is smaller than the load impedance. It highlights the importance of avoiding input balancing transformers for LF response and describes the use of a balanced amplifier powered by a battery to mitigate common mode interference.