I forgot the URL http://g4jnt.com/10MHzDist.pdf
Andy www.g4jnt.com On Sun, 28 Nov 2021 at 18:39, Andy Talbot <andy.g4...@gmail.com> wrote: > The way I look at short term stability is to multiply up to microwave > frequencies then mix the two and look at the resulting beat note. The > popular ADF4351 Fract-N synthesizer is ideal for this. Take two of them, > and programme for two frequencies in the GHz region a 1kHz or so apart when > driven by the two 10MHz freqs that are being compared Apply the two > multiplied signals to a mixer, and look at the resulting IF product with a > PC soundcard input. Using spectral analysis software with a waterfall > display, such as Spectran or Spectrum Lab you can look at the multiplied > frequency instability in real time. > > An example of the techniques used on a range of 10MHz reference sources > can be found here (I used a different Fract-N synth with a smaller setting > grid possible than the ADF4351 can give, but the same idea applies) > > > Andy > www.g4jnt.com > > > > On Sun, 28 Nov 2021 at 18:19, Erik Kaashoek <e...@kaashoek.com> wrote: > >> As the collection of frequency sources and counters in my home lab is >> growing I'd like to understand the performance of the frequency sources. >> Two different GPSDO do help to check long term stability. >> But the Rubidium frequency standard I have (Accubeat AR60A) is fairly >> unknown and seemingly not of good reputation, more specifically its >> (very) short term stability is doubted. >> So how best to check very short term (below 1s) frequency stability. >> The frequency counters available loose resolution quickly when the gate >> time is reduced below 1 second and high performance phase noise >> measurement equipment is not available so google helped with a search >> for alternative measurement methods. >> What I found was a method using two frequency sources, one of the two >> being a VCO, a mixer and some filters and amplifiers. >> By weak locking (large time constant) the VCO source using the mixer as >> phase detector to the other source, the output of the mixer's IF port >> should carry a voltage real time proportionally to the phase difference >> and by filtering and amplifying it should be possible to check for >> variations in the 1ms-1s range. >> Maybe even a scope can see the variations. >> When you know the amplification and the full range voltage you can even >> do an absolute measurement. >> Would this method work? >> Any specific concerns to take note of when doing the measurement? >> Removing the DC component (or locking the VCO such that there is no DC >> component) will be crucial I guess but given the slow speed of the loop >> even an ADC->computer->DAC->VCO setup can work. >> Any suggestion is welcome. >> Erik. >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe >> send an email to time-nuts-le...@lists.febo.com >> To unsubscribe, go to and follow the instructions there. > > _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.