Ken and I have been talking this over off-line, and it seems like an important thing to note is that the HP / Agilent spectrum analyzers tune over a measurement range by continuously sweeping their local oscillator. Setting a resolution bandwidth and a span width does not mean that the analyzer will tune in discreet hops. Even under external HP software control, the analyzer firmware still does (perhaps a series of) analog sweeps.
OTOH, if you use your own software, specify a resolution bandwidth, and then send a series of "tune, measure, tune,..." commands, then you can miss emissions between the skirts of the passbands if your step size is too large. You have to understand how your receiver or analyzer actually covers a frequency range. Regards, Ed Ed Price ed.pr...@cubic.com Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military & Avionics EMC Services Is Our Specialty Shake-Bake-Shock - Metrology - Reliability Analysis >-----Original Message----- >From: HALL,KEN (HP-Roseville,ex1) [mailto:ken_h...@hp.com] >Sent: Friday, December 07, 2001 8:38 AM >To: 'Pettit, Ghery'; HALL,KEN (HP-Roseville,ex1); 'John Woodgate'; >emc-p...@majordomo.ieee.org >Subject: RE: Stepping receiver, step sizes. > > > >Hello Gary and all, > >The point is do an experiment with your Stepping receiver. > >Ken > >-----Original Message----- >From: Pettit, Ghery [mailto:ghery.pet...@intel.com] >Sent: Friday, December 07, 2001 8:36 AM >To: 'HALL,KEN (HP-Roseville,ex1)'; 'John Woodgate'; >emc-p...@majordomo.ieee.org >Subject: RE: Stepping receiver, step sizes. > > >Ken, > >A spectrum analyzer sweeps through a range of frequencies. >The resolution >of the display merely impacts the accuracy of the frequency >determination >for a signal when digitized and sent to a computer over the >bus. Each point >on the display simply shows the highest level obtained in the >range covered >by that point. This is different than step tuning a receiver. > >Or am I missing something? > >Ghery Pettit >Intel > >-----Original Message----- >From: HALL,KEN (HP-Roseville,ex1) [mailto:ken_h...@hp.com] >Sent: Friday, December 07, 2001 8:09 AM >To: 'John Woodgate'; emc-p...@majordomo.ieee.org >Subject: RE: Stepping receiver, step sizes. > > > >Hello all, > >We typically measure in 500 MHz spans, our spectrum analyzer >has 400 bits so >1.25 MHz/bit. Concerned that we could miss an emission I >perfromed the below >experiment, try it: > >Injected a 2950 MHz signal into EMI Receiver, set for 1MHz >RBW, and measured >it using diffrent Spans > >3 000 MHz 67 dBuV signal, 400 bits 1 MHz RBW >Span [MHz] Amplitude Step/bit [MHz] >10 66 0.025 >500 67 1.25 >1000 67 2.5 >2000 67 5 >3000 66 7.5 >4000 67 10 >6000 67 15 > >What we see is even with the step size 15 times the RBW the >signal is not >lost. > >Regards, > >Ken Hall > > > >-----Original Message----- >From: John Woodgate [mailto:j...@jmwa.demon.co.uk] >Sent: Thursday, December 06, 2001 2:16 PM >To: emc-p...@majordomo.ieee.org >Subject: Re: Stepping receiver, step sizes. > > > >I read in !emc-pstc that Ken Javor <ken.ja...@emccompliance.com> wrote >(in ><20011206195802.LCFL6698.femail7.sdc1.sfba.home.com@[65.11.150.27]>) >about 'Stepping receiver, step sizes.', on Thu, 6 Dec 2001: >>Keeping the step size to one-half the measurement bandwidth >is an accepted >>way of assuring that all possible signals are captured. >Using a step size >>equal to a measurement bandwidth is not quite as good but reasonable. > >In the context of 8, 20 or 80 kHz steps to cover 4 GHz, I think >reasonableness wins. One would be extraordinarily unlucky to lose a >significant signal under those conditions. >-- >Regards, John Woodgate, OOO - Own Opinions Only. >http://www.jmwa.demon.co.uk > >After swimming across the Hellespont, I felt like a Hero. > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
