Hi Ed, Actually, 110MHz sounds like a nice round number to me -- it's a couple of MHz above the top end of the (American) FM broadcast band.
Maybe the writers didn't know what upper limit to use, and someone said "Let's make sure broadcast engineers & technicians are protected, since they may spend a lot of time near antennas." Pat Lawler EMC Engineer SL Power Electronics Corp. "Price, Edward" <[email protected]> wrote on 08/18/2011 06:49:39 PM: > I have been reading through ANSI C95.1-2005 with an interest toward > the limitation of RF contact voltage, which leads me to Paragraph 4.5. > > But here’s where I get confused, For instance, I have a 230 MHz > intentional emitter that has a peak power of about 20 Watts, albeit > with a fairly low duty cycle that yields a much lower average power. > This emitter uses several antennas, from a fixed 5/8 wave vertical > rod to an electrically short, man-worn, rubber ducky whip. > > So, I drill into Paragraph 4.5 to find an MPE in the frequency range > of 100 kHz to 3 GHz. Odd, it only seems to provide a voltage limit > of 140 Volts open-circuit for the frequency range of 100 kHz to 100 > MHz. But, there is nothing mentioned for 100 MHz through 3 GHz. > > Just as in my other post about induced currents, why is 100 MHz > chosen as an arbitrary upper limit of regulation and guidance? Was > 100 MHz chosen for some good physical reason, or is it possibly a > limit based on the measurement technique? It just doesn’t make any > sense that there would be no concern about frequencies >100 MHz! > > > > As an aside, the text of Paragraph 4.5 states “this standard also > specifies an MPE for the open circuit voltage that exists on objects > exposed to electric and magnetic fields.” The “objects exposed to” > phrase gives me pause; that sounds to me like any object the field > illuminates, but not the radiating element itself. > > > > Thus, this seems to me like a limit on induced voltages in all other > conductive objects, but not on the antenna itself. So, is there any > guidance anywhere about the maximum permissible voltage on an > antenna element that might be reasonably expected to be touched by a human? > > > > Am I missing something elsewhere in the ANSI spec, or should I be > looking elsewhere for guidance? Thanks in advance for any comments! > > > > > > Ed Price > > [email protected] WB6WSN > > NARTE Certified EMC Engineer > > Electromagnetic Compatibility Lab > > Cubic Defense Applications > > San Diego, CA USA > > 858-505-2780 > > Military & Avionics EMC Is Our Specialty > > - ---------------------------------------------------------------- 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://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html 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]>
