Airborne VLF data are mainly used for the interpretation of large scale geological features such as faults and conducting rock units, although under favourable circumstances, smaller conductors such as due to sulphide mineralization may be revealed. VLF data are regarded as an excellent, cost-effective complement to airborne magnetic data.

RMS Instruments' HERZ TOTEM-2A VLF Electromagnetic System has an established record of outstanding performance and reliability in airborne installations worldwide. The TOTEM-2A receives the magnetic component of fields radiated from one or two VLF transmitters in the 15-25 kHz (alternatively, 10-30 kHz) frequency range. These transmitters are located around the world for the purposes of navigation and communications with submarines. The parameters normally measured are the change in total field and the vertical quadrature component, and the total field gradient from dual sensors. The sign of the quadrature polarity is also recorded.

Outstanding features:

• Automatic measurement of two VLF stations -- Allows detection of geological strikes in almost any direction, and results in high confidence in the data collected and their interpretation.
• Accurate frequency selection -- Line and Ortho channels can be selected individually in 100-Hz steps.
• Wide signal bandwidth -- Accommodates modulation and some offset, without introducing severe noise.
• Field strength compensation -- Each channel level is independently adjustable to the nominal 100% total field.
• Gradiometer configuration -- Enhances interline contouring and delineation of multiple conductors.

HERZ TOTEM-2A VLF Electromagnetic Receiver Data Sheet