>-----Original Message----- >From: John Harrington [mailto:[email protected]] >Sent: Monday, May 05, 2003 7:44 AM >To: '[email protected]' >Subject: ELF (E and H) survey equipment > > > >Does anyone know where I might be able to rent (and failing >that purchase) >some E and H field survey eqipment? I need it to range from sub 1Hz to >10kHz, to read E and H fields separately, and to be portable. > >Thanks > >John Harrington >EMC Technical Manager >F-Squared Laboratories
That's an interesting task! I noticed that an old Stoddart NM-40A, which could measure to microvolts >from about 20 Hz to 50 kHz, just sold on eBay for under $100. An old NM-40A, an active E-field probe and an H-field loop antenna could get you much of the way to doing your measurements. But, getting a bit more modern, you could also use a decent digital oscilloscope with FFT capability. That would cover from 10 kHz down to sub 1 Hz all by itself. Then, all you need are probes. Now here, I'm getting a little bit out of my range, so I invite any assistance or corrections. But it seems that you could get E-field by using something like a 41" rod & counterpoise, which is electrically 1/2 meter. Use a very high impedance, bandwidth limited FET amplifier, calibrate the gain, and remember to add 6 dB for the 1/2 meter electrical length. For H-field, sub 1 Hz loops are a bit of a problem, but still a classical solution. You might try to get exotic with something like reading the voltage across a low resistance in series with a loop coil. You might try researching "natural radio", where hobbyists have done a lot of work on low-noise, ultra low-frequency receivers and active antennas. Look at http://www.auroralchorus.com/natradio.htm Regards, Ed Ed Price [email protected] NARTE Certified EMC Engineer & Technician Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military & Avionics EMC Is Our Specialty This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
