Intentional use of power wiring for communications is one thing, but aircraft ADF reception as a rationale for ITE CE control is a bit of a stretch, and that is a bit of an understatement. ADF homes in on intentional broadcasts >from 190 kHz through the AM band. ADF receivers are quite insensitive, only an intentional broadcast could cause a response. It certainly does make sense to control CE on the AIRCRAFT electrical bus, and it is no surprise that RTCA/DO-160 does so from 150 kHz to 30 MHz.
From: "Pettit, Ghery" <[email protected]> List-Post: [email protected] List-Post: [email protected] List-Post: [email protected] List-Post: [email protected] Date: Tue, 29 Apr 2003 10:32:20 -0700 To: "'Ken Javor'" <[email protected]>, "'[email protected]'"<[email protected]>, "Andre, Pierre-Marie"<[email protected]> Cc: [email protected] Subject: RE: FCC Limits Ken, The FCC made the change for several reasons, international harmonization being foremost. We do have users of the RF spectrum below 450 kHz in the US. The ADF receivers in the airplanes I fly tune in non-directional beacons below that frequency. I'd really rather home in on one of those as opposed to your PC (although there is a rather large difference in the signals, but...). The only significant opposition in the Rule Making came from some interests who wanted even lower limits to lower frequencies. They were not successful. Manufacturers of ITE with international markets supported the change as they were already testing to the CISPR 22 limits and this was a non-issue to them. Ghery Pettit Intel Corporation From: Ken Javor [mailto:[email protected]] Sent: Tuesday, April 29, 2003 10:02 AM To: Pettit, Ghery; '[email protected]'; Andre, Pierre-Marie Cc: [email protected] Subject: Re: FCC Limits Forum Members, I am interested in opinions on the matter of the FCC changing their CE limits to include frequencies down to 150 kHz. My concern is predicated on the following assumptions: a) CISPR 22 controls to 150 kHz because European radios broadcast down to that frequency. That is called the long wave band. In North America, AM broadcasts are confined to the medium wave band. The 450 kHz cut off includes the AM band IF. b) (Most?) European single phase power is 220 Volts, 50 Hz. The transformers in radio power supplies have a different turns ratio than for American single phase power at 120 Volts. c) In my experience, a generic 50/60 Hz transformer works just as well at 150 kHz as it does at the power line frequency. In view of the above, it is not obvious to me why the FCC adopted CISPR 22 CE limits. Does anyone know if LW broadcasts are planned for North America? If that were to happen, the CISPR 22 limits at 150 kHz would need to be reduced roughly 6 dB, to account for the reduced turns ratio in power supplies built for North American power. European transformers would attenuate power line ripple more than American transformers would. Appreciate inputs. Ken Javor From: "Pettit, Ghery" <[email protected]> Reply-To: "Pettit, Ghery" <[email protected]> List-Post: [email protected] List-Post: [email protected] List-Post: [email protected] List-Post: [email protected] Date: Tue, 29 Apr 2003 08:25:00 -0700 To: "'[email protected]'" <[email protected]>, "Andre, Pierre-Marie"<[email protected]> Cc: [email protected] Subject: RE: FCC Limits The new limits are the same as the limits in CISPR 22. Another source for the FCC Rules (updated monthly on CD-ROM) is Pike & Fischer at www.pf.com <http://www.pf.com/> . Not cheap, but I've always got the latest and greatest in my laptop. Plus, it's in a Windows application, so I can cut and paste (as done below) into other documents. Saves a lot of re-typing... Ghery Pettit Intel Corporation §15.107 Conducted limits. (a) Except for Class A digital devices, for equipment that is designed to be connected to the public utility (AC) power line, the radio frequency voltage that is conducted back onto the AC power line on any frequency or frequencies within the band 150 kHz to 30 MHz shall not exceed the limits in the following table, as measured using a 50 mH/50 ohms line impedance stabilization network (LISN). Compliance with the provisions of this paragraph shall be based on the measurement of the radio frequency voltage between each power line and ground at the power terminal. The lower limit applies at the band edges. Frequency of Conducted limit (dBmV) emission (MHz) Quasi-peak Average 0.15-0.5 66 to 56* 56 to 46* 0.5-5 56 46 5-30 60 50 * Decreases with the logarithm of the frequency. (b) For a Class A digital device that is designed to be connected to the public utility (AC) power line, the radio frequency voltage that is conducted back onto the AC power line on any frequency or frequencies within the band 150 kHz to 30 MHz shall not exceed the limits in the following table, as measured using a 50 mH/50 ohms LISN. Compliance with the provisions of this paragraph shall be based on the measurement of the radio frequency voltage between each power line and ground at the power terminal. The lower limit applies at the boundary between the frequency ranges. Frequency of Conducted limit (dBmV) emission (MHz) Quasi-peak Average 0.15-0.5 79 66 0.5-30 73 60 (c) The limits shown in paragraphs (a) and (b) of this section shall not apply to carrier current systems operating as unintentional radiators on frequencies below 30 MHz. In lieu thereof, these carrier current systems shall be subject to the following standards: (1) For carrier current systems containing their fundamental emission within the frequency band 535-1705 kHz and intended to be received using a standard AM broadcast receiver: no limit on conducted emissions. (2) For all other carrier current systems: 1000 mV within the frequency band 535-1705 kHz, as measured using a 50 mH/50 ohms LISN. (3) Carrier current systems operating below 30 MHz are also subject to the radiated emission limits in §15.109(e). (d) Measurements to demonstrate compliance with the conducted limits are not required for devices which only employ battery power for operation and which do not operate from the AC power lines or contain provisions for operation while connected to the AC power lines. Devices that include, or make provision for, the use of battery charges which permit operating while charging, AC adaptors or battery eliminators or that connect to the AC power lines indirectly, obtaining their power through another device which is connected to the AC power lines, shall be tested to demonstrate compliance with the conducted limits. From: [email protected] [mailto:[email protected]] Sent: Tuesday, April 29, 2003 7:34 AM To: [email protected] Cc: [email protected] Subject: Re: FCC Limits In a message dated 4/29/2003 9:01:17 AM Central Daylight Time, [email protected] writes: You can visit : http://www.access.gpo.gov/nara/cfr/waisidx_01/47cfr15_01.html Good luck Pierre-Marie Andre Senior Approval Engineer Thanks, but this is the old limits. The new conducted limits are being lowered to 150 kHz I believe. It's this info I'm looking for. Derek N. Walton Owner L F Research EMC Design and Test Facility Poplar Grove, Illinois, USA www.lfresearch.com
