MANY years ago when I ran the Amador lab in Colorado, we had a well-known RFID customer whose tags read at 150 kHz. Measurement distance for the FCC limit was 300 meters. It just happened that the far corner of our 8-acre property was very close to 300 meters as measured by my mountain bike's odometer (before cheap accurate GPS). Honda generator, R&S loop and receiver in tow, I made measurements at 300, 100, 30 and 10 to establish the fall off curve. It was close to 60 dB/decade and the FCC accepted my curve for subsequent measurements. "Near field" is a very long distance at that frequency!
Brent G DeWitt, AB1LF Milford, MA -----Original Message----- From: Cortland Richmond [mailto:[email protected]] Sent: Monday, February 27, 2017 9:14 PM To: [email protected] Subject: Re: [PSES] CORRECTION (wrong page) Passive Loop Emissions [General Use] On 2/27/2017 7:53 PM, Brent DeWitt wrote: > I think Ken's rational makes sense to me, since the 51.5 is derived from > 20*log(377). > > Sure, but now we're back to how close we are -- wavelengths -- to the emitter. 20*log(??) Low frequencies can be tricky, and I once had to double-check a test lab (not yours) results at a vendor, dragging the EUT out to their parking lot then wheeling a cart with a 6510 loop antenna, battery, AOR AR5000 receiver and RMS voltmeter [all mine] away to see how fast the signal dropped with distance compared to 3m. A fun time was NOT had, but I probably came across as a mad scientist. Again. At least no one ran out of a chamber... Cortland Richmond KA5S - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]> --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
