Ken, I'm curious about the origin of the -174dBm. _____________________________________________________________________________________
Ralph McDiarmid | Schneider Electric | Renewable Energies Business | CANADA | Compliance Engineer From: Ken Javor <[email protected]> To: [email protected] List-Post: [email protected] List-Post: [email protected] List-Post: [email protected] Date: 05/26/2010 10:38 AM Subject: Re: [PSES] Radiated emission testing for automotive at low levels. ________________________________ Noise floor (dBm) = -174 dBm + 10*log (BW) + F (dB) At room temperature, where F is noise figure. If F isn’t given, but a noise floor is given with a stated BW, then using the above equation, you can get the noise floor at any other BW using: Noise floor (dBm) = Noise floor at stated BW (dBm) + 10*log (BW desired/BW stated) Keep in mind, as someone else noted, that receiver manufacturers often state noise floor as “displayed average noise level.” That uses video averaging, which isn’t allowable if making a peak detection measurement. You can add about 12 dB for the difference between DANL vs. peak detection, other things (BW) equal. Ken Javor Phone: (256) 650-5261 ________________________________ From: "ce-test, qualified testing bv - Gert Gremmen" <[email protected]> List-Post: [email protected] List-Post: [email protected] List-Post: [email protected] Date: Wed, 26 May 2010 13:24:43 +0200 To: <[email protected]> Conversation: Radiated emission testing for automotive at low levels. Subject: RE: Radiated emission testing for automotive at low levels. Hello Friends, Collegues, Thanks to all of you for help, comforting words en correcting some misconceptions on my side. My conclusions are: * * * * *Nothing wrong with my analyser, -71 dBm is quite normal * * * * *I need more gain and less losses into cabling (the latter had already my attention before with immunity testing) * * * * *More gain into more efficient antenna’s (= lower antenna factors) * * * * *More gain = Have a “better” pre-amp, instead of 24 dB, I might need 45 or 50 dB of gain and where possible, less noise * * * * *Limits have been over specified in some cases To illustrate this last point, manufacturer has come up with relaxed requirements after I mentioned that the noise exceeded the limit lines. As a last question: How can I predict the noise floor from the analysers specification (-154dBm at 10H Regards, Ing. Gert Gremmen [email protected] <mailto:[email protected]> <mailto:[email protected]> www.cetest.nl <www.cetest.nl> Kiotoweg 363 3047 BG Rotterdam T 31(0)104152426 F 31(0)104154953 Before printing, think about the environment.
