Leigh, A narrow filter around 10MHz is likely to show phase ripple in its passband, and that will most certainly vary over temperature, not a good thing for ADEV, that's why a LPF is preferred.
Also, most crystal filters may not be happy with the output level of a typical OCXO, so you would have to attenuate the signal before the filter and amplify it after, an unnecessary complexity that will not help ADEV. Crystal filters are not usually used for harmonic suppression because away from the resonance, crystals are good capacitors, so you will probably not find much data, and if you find data, it will probably suck :) In most applications, they are preceded and followed by L-C filters to normalize the out-of-band response. Didier ------------------------ Sent from my BlackBerry Wireless thingy while I do other things... -----Original Message----- From: "Leigh L. Klotz, Jr. WA5ZNU" <le...@wa5znu.org> Sender: time-nuts-boun...@febo.com Date: Wed, 23 Jun 2010 13:44:37 To: Discussion of precise time and frequency measurement<time-nuts@febo.com> Reply-To: Discussion of precise time and frequency measurement <time-nuts@febo.com> Subject: Re: [time-nuts] FRS-C TTL / sine outboard filter question > ... >> [snip] > If you need a sine wave output but don't want to change anything inside, > just add a lowpass filter. > A 5th order LPF (three inductors/ 2 caps or vice versa) should give you > a clean sine wave output. > Just add a coupling cap to remove the DC component. > > Adrian > > _ Thank you, Adrian. I'll pursue both options, internal fixes and external filter. A multi-pole LPF is easily understood, and I don't believe I care about passband ripple, though I wonder a little about the effect of the coupling on phase changes (i.e., does this have any unfortunate effect on adev?). I still don't know if a crystal ladder filter will suppress the harmonics, but I did get the answers that make me not need to ask anymore (1. fix the internal filter, 2. use the high Q xtal filter for optional removal of close-in noise) Given time I would do all of these things, but I may not get to them all! Leigh. _______________________________________________ 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. _______________________________________________ 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.