This project is intended to make available to those individuals who may desire to participate in  the research  and experimentation of the study of extremely low frequency signals which travel through the interior of our earth,  the opportunity to construct a receive station to be used to collect
data for analysis.

As individual stations come on line, this data will furnish parameters such as frequency, signal strength, and location to a centralized computer which will be able to precisely determine the location, what type of event, and how strong. This will be useful for earthquake precursor studies and other
transient events. The frequencies of interest are those ranging from .001 hz to 45 hz.

In order to achieve this goal it will be necessary to have most of the equipment and construction parameters standardized  as much as possible. The Elfrad Group will furnish schematics, software and parts lists, plus support.

A complete standardized ELFRAD monitoring station consists of these components:

1. Antenna array - Two widely spaced probes to be placed into the earth.
                            These may consist of copper clad ground rods eight feet
                            in length, or a copper conductor strip in the earth.

2. ULF Receiver - Either a pre built unit may be purchased or  a circuit 
                            board with schematics are available.

3. Interface Card - A multi-channel analog to digital interface unit to couple
                             the received signal to the data computer.

4. Data Computer- A standard PC type computer and monitor.

The costs for this project may be kept at a minimum as a lot of you will be able to build most of the necessary items. The most expensive components will be the data collection computer and analog to digital interface card.  A PC type of computer is recommended with at least a 66 mHz CPU.  The software program for the A/D card is DOS based. The interface card for data collection is manufactured by an outside source. It contains 8 input channels, and an input for direct connection to a short wave radio tuned to WWV, which keeps the data card and computer synched to within plus or minus 2 milliseconds. Also if desired, a GPS type of time standard is available.  

The over all description of the receive site setup and operational information is as follows:

The desired signals are recovered from the earth and are directed to a conditioning circuit which not only protects the receive equipment from transients caused by lightening and other sources but attenuates most of the ambient 60 or 50 hz frequency caused by commercial power. The signal then passes through an isolation circuit which removes any ground loop problems which may occur at your computer interface. Then the desired frequencies pass through a series of filters to remove
most of the noise and unwanted signals above 25 hz.

This band of signals then is coupled to the interface card of the data processing computer to be recorded on the hard drive.  The card will accept up to six channels of data and samples the signal delivered to it at 100 samples per second, records them and then are displayed on the computer screen either in real time or compressed time format.  At any time it is possible to take any period of data previously recorded, generate a file and display the data for analysis.  You are also able to post filter the data, with band pass, notch, low pass, and high pass capability.  ©1998