recording ultra low frequency ULF 2

[gek007]

i want to record ultra low frequency ULF with a sound card on a PC and be able to play it back. the frequency is in the range of 4-10 Hz. is there any equipment readily available to do this? or any suggestions how to make one? i have read where you can do this with a transducer but i don't know how to make it.
thanks

 

[logbook]

I am not sure I am following your question correctly here. Is it that you are trying to record 10Hz electromagnetic waves? If this is true then the first thing you need is an antenna (aerial). At this frequency a dipole would either be huge or very ineffective. I would therefore suggest using a large coil of wire, the larger the diameter the better. By large I mean 1 meter or bigger if possible. This is your "transducer".

I think the signal will be swamped by 50Hz/60Hz mains pickup so you will need to filter out those components using a low pass filter. Given that you want to see 10Hz and not see 50Hz the filter will need to have a steep roll-off characteristic. In technical terms we would say it has to have 3 poles or more. You can then use a freely available software program on your pc to record the signal via the sound card. I like "Wavepad" (

http://www.nch.com.au/wavepad/)

 

[Higgler]

I hope the 4-10 hz is not RF. a 10 hz antenna is a quarter wavelength when it's 4600 miles long. That's a big fella, fairly heavy too. You'll need to lay it out on the Great Wall of China.
Little ferrite loaded am radio antennas are typically 4 inches long for 1 Mhz frequency, so that makes your antenna 400,000 inches long, or 6 miles long.
This must be acoustic or you already have the signal in coax. somewhere and just need electronics to A/D convert it and store it, I hope.
kch

 

[rosetta]

Ultra low frequency (ULF) signals are being monitored by professionals and "amateurs" already using a variety of devices. The DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) satellite is monitoring ultra-low frequency electromagnetic signals. This is a rather small satellite and it uses a 3-axis "antenna". Can't determine from the site pages what they are using for a "receiver".

http://smsc.cnes.fr/DEMETER/

http://smsc.cnes.fr/DEMETER/GP_actualite.htm

There are some "receivers" and "antennas" described in the files section of the Yahoo ULF/ELF forum.

There is a receiver diagram at the ELFRAD site

http://www.elfrad.com/

"Receivers and Antennas" page. The antenna page discusses using an "earth" antenna, but other members of this group are using large inductor coils as antennas.

You might do a search on the acronym CSAMT (Controller-Source Audio-Frequency Magnetotelluric) for commercial transmitters, receivers and antennas for the below 10 Hz range.

There are no FCC controls on emissions at these low frequencies, thus detected "emissions" can be either from natural or artificial sources. The CSAMT transmitters are at 15 KW plus and I don't think anybody is determining just how far their "pulses" are transmitted.