Active Loop AAA-1 Performance at VLF and LF
Performance analysis and measurement data for the LZ1AQ AAA-1 active loop antenna at VLF and LF
Description
Investigates the performance characteristics of the AAA-1 active loop antenna across Very Low Frequency (VLF) and Low Frequency (LF) bands. It details the antenna's frequency response, explaining how a small loop with a low input resistance trans-impedance amplifier maintains a flat frequency response to electromagnetic field intensity E. The document illustrates current source and Thevenen equivalent circuit models for small loops, emphasizing the transition between these models based on frequency and load impedance. Measurement setups for both high frequency and VLF/LF responses are presented with diagrams, including methods for simulating current and voltage sources.
The analysis includes normalized plots of the AAA-1's frequency response for three distinct loop inductances, derived from measurements using a Perseus SDR at 1 kHz bandwidth. It provides calculations for the noise floor at VLF/LF frequencies, comparing ambient noise levels with the antenna's internal noise floor. The resource also documents practical reception experiments in a semi-urban environment, showcasing successful reception of time transmitters like MSF at 60 KHz and SAQ at 17.2 KHz, along with various navy digital transmissions and Russian Alfa beacons.