Of course, there are PICTIC II, DMTD, DDMTD, SR620, HP5370B, Wavecrest, PM6681, HP53132. The simplest is using a scope and... wait.
On Thu, Apr 19, 2012 at 9:53 PM, Bruce Griffiths <bruce.griffi...@xtra.co.nz > wrote: > Use a dual mixer system with an offset LO. > > Bruce > > Azelio Boriani wrote: > >> And, if you are measuring, by analog mixing, two very slightly different >> frequencies, what do you expect to obtain if not a signal that is slow, >> very slow. How can you measure milliHertz or microHertz without waiting? >> >> On Thu, Apr 19, 2012 at 9:31 PM, Magnus Danielson< >> mag...@rubidium.dyndns.org> wrote: >> >> >> >>> Hi Wolfgang, >>> >>> >>> >>> On 19/04/12 21:10, skywatcher wrote: >>> >>> >>> >>>> Hello @all, >>>> >>>> my name is Wolfgang and i'm new to the list. :) >>>> >>>> >>>> >>> Welcome! >>> >>> >>> >>> I want to measure the frequency difference between a 10 MHz OCXO and a >>> >>> >>>> 10 MHz Rubidium. >>>> I think that's what many people here have done many times... but i don't >>>> want to use expensive >>>> equipment like time interval counters with picosecond resolution etc. I >>>> would prefer a cheap and >>>> easy solution. I also would like to have an update rate of more than 1 >>>> measurement per second, >>>> or even more. >>>> >>>> My first approach was to use a simple XOR phase comparator. I tried a >>>> 74HCT86 and a 74HCT4046. >>>> It works, but it's very noisy, so i don't get better than about 10 mHz >>>> frequency resolution. >>>> If i look at the lowpass-filtered output i don't see a nice sine or >>>> triangular wave, but it looks more >>>> than a triangular wave with round tops and some bumps between them. >>>> Another problem is that the >>>> difference frequency gets very low when the frequencies are very close, >>>> so it's not enough to look >>>> only for zero crossings of the difference signal. >>>> >>>> Does anybody know a possibility to get a resolution< 1 mHz ? >>>> >>>> >>>> >>> Have you looked at the PICTIC II project? It's not too bad. >>> >>> There is several other possible projects to consider, but the PICTIC II >>> may be a good start. Also look at a divide down system such as the TADD 2 >>> divider or the just released TADD 2 Mini. >>> >>> There is a challenge in doing fairly high precission for low budget here >>> on the list. Besides measuring frequency, we pride ourselves in measuring >>> the frequency stability, Allan Deviation (ADEV), as good as possible. >>> >>> Cheers, >>> Magnus >>> >>> >>> >>> _______________________________________________ >>> 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. >> >> >> > > > _______________________________________________ > 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.