Hi John, Thank you for your email. I am also looking at the PM method to solve my problem. I have a HP signal generator and I can use it to generate an RF signal and then modulate it with noise from the modulating input of the signal generator. I need some suggestion regarding the noise generator. I don't have one and I never used one before. Any ideas regarding the noise generation.
Cheers Bilal ----- Original Message ----- From: "John Miles" <[EMAIL PROTECTED]> To: "Discussion of precise time and frequency measurement" <[email protected]> Sent: Saturday, March 03, 2007 1:13 AM Subject: Re: [time-nuts] Suspected Spam: External clock for Analog toDigital Converter in GPSRx front-end Rx front-end > Possibly, if the ready-made spread-spectrum clocks provide enough jitter > for > him. It shouldn't be hard to do it to an existing clock, though. > > The article by David Chu on time-interval averaging in the June '74 HP > Journal issue talks a little about why phase modulation is preferable to > FM > when you want to deliberately add jitter to a carrier. A frequency > modulator imposes a rolloff characteristic that shapes the spectral > characteristics of the noise source in ways that you might not want, while > making it harder to avoid changing the carrier's average frequency as well > as its instantaneous phase. He also points out that it's easy to add PM > jitter by applying noise to a varactor-tuned tank circuit across the > signal > path. It all seems obvious and straightforward enough. > > Remember that the computer guys don't care what their average frequency is > to any real degree of precision, because everything else is ultimately > slaved off the main CPU clock. If you use an FM technique and the > modulating function isn't absolutely symmetrical, or the modulator > response > itself is the least bit nonlinear, you will have to use a separate > low-bandwidth PLL to keep the mean carrier frequency where you want it, > I'm > thinking. Way too complicated, considering the advantages of the PM > technique. > > -- john, K5FX > > >> -----Original Message----- >> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] >> Behalf Of Hal Murray >> Sent: Friday, March 02, 2007 1:17 AM >> To: Discussion of precise time and frequency measurement >> Subject: Re: [time-nuts] Suspected Spam: External clock for Analog to >> Digital Converter in GPSRx front-end Rx front-end >> >> >> >> > How about using one of the "spread-spectrum" microprocessor clock >> > generator IC's? These add a pseudo-random jitter to the clock signal >> > so the interference from the equipment is slightly spread causing the >> > equipment to pass EMC testing by causing an apparent reduction in the >> > peak due to the bandwidth of the test receiver. >> >> I thought it was FM by a sawtooth, or something simple like that. >> >> I could easily have a fuzzy memory and/or there could be several >> techniques >> in use. >> >> -- >> These are my opinions, not necessarily my employer's. I hate spam. >> >> >> >> >> _______________________________________________ >> time-nuts mailing list >> [email protected] >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> > > > _______________________________________________ > time-nuts mailing list > [email protected] > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
