Ed, I have no special knowledge of the standard to which you are working, but you and I and everyone on this forum knows that a conducted measurement at an antenna port is much superior in accuracy and much quicker to make than a radiated measurement. The only added complexity is a tuned notch filter to protect the receiver, if necessary. Further, EIRP means the transmit power multiplied by the main lobe gain of the attached antenna. Presumably someone knows that main lobe gain, so all you need is the transmit power.
Also, if possible I would make that conducted measurement with a 1 MHz bandwidth, no extrapolation necessary there either. Your sweeps will (theoretically) take about 100 us. I believe the fastest sweeps most analyzers make is about 20 ms. You can use no video filtering at all, put the analyzer on max hold and just wait to see if anything crops up. If it doesn't you're done. If something does crop up, then you can zoom in on it and maybe do a zero span and check its duty cycle. Also I am guessing that this limit protects GPS reception. I would be careful of extrapolating a 10 kHz measurement to 1 MHz, if it doesn't extrapolate that way on the screen. GPS or whatever it is that has this wide bandwidth is desensitized by the sum total of all power within its bandwidth, and extrapolating a 10 kHz signal to 1 MHz will overestimate the in-band power by orders of magnitude if the signal isn't actually 1 MHz wide. Ken Javor From: "Price, Ed" <[email protected]> List-Post: [email protected] Date: Thu, 26 Apr 2007 08:58:24 -0700 To: "'IEEE EMC & SAFETY PSTC'" <[email protected]> Subject: FCC R&R Part 25 I have a couple of questions about testing Land Mobile Ground Stations in accordance with FCC R&R, Part 25. Section 25.216(i) says: The peak e.i.r.p density of carrier-off state emissions from mobile earth stations manufactured more than six months after Federal Register publication of the rule changes adopted in FCC 03283 with assigned uplink frequencies between 1 and 3 GHz shall not exceed -80 dBW/MHz in the 15591610 MHz band averaged over any 2 millisecond active transmission interval. Since the FCC says "eirp" density, the I assume that means that the signal is to be measured as it radiates from the EUT. (The EUT has a separate discrete antenna, connected to the EUT by a length of coax cable.) Am I correct that I can't measure the "eirp" density by looking into the coax cable; that I have to do a measurement of the radiated field? Do the units of "dBW/MHz" imply that, if I measured using a 10 kHz resolution bandwidth, I would have to add a bandwidth factor of 20 dB to normalize the observed data to a 1 MHz bandwidth? Finally, how does one take a 2 millisecond "average"? Thanks in advance! Ed Price [email protected] WB6WSN NARTE Certified EMC Engineer & Technician Electromagnetic Compatibility Lab Cubic Defense Applications San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (FAX) Military & Avionics EMC Is Our Specialty - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] 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] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________ - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] 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] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
