Mike, I agree with you that for SatCom application, long term stability is not as much of a concern, phase noise typically is the main issue.
But I suspect that for a time nuts looking at stability over periods of hours or days, temperature effects cannot be ignored. Passband ripple usually goes with group delay ripple, and that delay will change with temperature. For instance, on the Tek 494P I have, the 30Hz crystal filter is thermostatically regulated. When the instrument is cold, there is no signal at all... Didier ------Original Message------ From: Mike Feher To: Time-Nuts To: Didier Juges via Cox Subject: RE: [time-nuts] FRS-C TTL / sine outboard filter question Sent: Jun 23, 2010 8:41 PM I do not understand why the passband ripple would be of any consequence in the big (or small as we typically talk about) picture. During any measurement interval, it will be a constant, for all practical purposes, including ours. A measurement at a different time, at a different temperature that may adversely affect where the ripple is, it will certainly create a slightly different amplitude and phase delay, however, again, a constant through the measurement process, not affecting the result. When we were designing the system I mentioned previously, both Dave and Fred of NIST were in assistance, as well as the staff of the relevant departments of MIT's LL, and no one saw any issues. Regards - Mike Mike B. Feher, N4FS 89 Arnold Blvd. Howell, NJ 07731 732-886-5960 -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Leigh L. Klotz, Jr. WA5ZNU Sent: Wednesday, June 23, 2010 6:15 PM To: did...@cox.net; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] FRS-C TTL / sine outboard filter question Thank you, Didier. That pretty much sums it up. I was aware of the signal level issue but didn't consider that passband ripple would be temperature sensitive. It's fun learning to think in the long time domain. In the meantime I've found a 10 mbit ethernet ISA card in my office and will follow Robert G8RPI's suggestion to use G4HUP's document to obtain a ready-made 10 MHz filter from it. Plus as a bonus the box had a BNC T connector in it. Leigh/WA5ZNU _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ------------------------ Sent from my BlackBerry Wireless thingy while I do other things... _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.