I also see terms like GPS tamed or PLL-GPS.
https://www.ebay.com/itm/1pcs-PLL-GPSDO-10M-GPS-tamed-clocks/263392170249?hash=item3d53659109:g:1p0AAOSwH3haNo7c
https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2047675.m570.l1313.TR12.TRC2.A0.H0.Xgps-pll.TRS0&_nkw=gps-pll&_sacat=0
It is not at all clear which one is what type and how it is designed.
Even in main well known brands, I understand PRS10 and sa.22C and fe5650 are
fundamentally different.
I guess they are all "GPS disciplined" in some way but for a newbie, telling
one apart from the other and picking a suitable architecture for the purpose is
very difficult.
---------------------------------------
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
On Wednesday, September 25, 2019, 9:28:29 PM EDT, Bob kb8tq <[email protected]>
wrote:
Hi
The first gotcah is that the distinction is not very clear. A TBolt varies the
frequency of
the OCXO in the GPSDO. GPSDO’s that use Rb’s can and often do vary the
frequency.
Indeed some devices use a DDS to generate an output rather than varying
something else.
I suspect that is what you are bumping into. In some cases a DDS feeds a
cleanup loop or filter
that restricts the output range.
If you are after low noise at 10 GHz, the multiplier chain needs to be
carefully designed. There
is a lot more to it than you might think. The first and most basic question
would be “is it a fixed
frequency output or tuned?”. From there you can head off in a number of
directions.
If you need to be able to change frequency from 1 MHz to 10 GHz in a few
nanoseconds, then
there is no alternative to using a DDS. If hat is part of the requirement then
you go from there. If
you want only 10 GHz +/- 0.001Hz then there are other, more quiet / lower spur
ways to do the job.
Indeed it goes on and on …..
Bob
> On Sep 25, 2019, at 4:45 PM, Taka Kamiya via time-nuts
> <[email protected]> wrote:
>
> This is a cross post from EEVBLOG. I'm hoping there is someone who's
> familiar with this subject would help me out here.
> I am hoping someone can help me understand this. I've seen similar
> discussions take place both for GPSDO with Crystal Oscillators and Rubidium
> modules. It appears there are two types of each.
> 1) fixed frequency type (less jitter)
> 2) frequency agile type (more jitter)
>
> I've read frequency agile Rb modules (ones you can change output frequency)
> is one kind of Rb (sa.22c and fe5650, etc), and there is another one that you
> cannot change frequency. (ie. T-bolt, PRS10, etc). Words like phase noise
> and PLL are thrown out often in discussions. I vaguely remember frequency
> agile types are less suitable if ultimate in stability is needed such as
> multiplying the output into GHz range. This discussion was about 10GHz
> transverter.
> Is this because frequency agile type has the ultimate output from PLL
> (subject to jitter) and fixed frequency type is from OCXO? If this is the
> case, why frequency agile type even exist? It's not like it can be used as a
> VFO (on radio).....
>
> I'm sorry this is SO vague but that's the reason for this post. I need to
> understand this. There was a wiki page on this, but it doesn't go into this
> discussion deep enough.
>
> Would someone help me gain knowledge in this?
>
> ---------------------------------------
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
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