When comparing a 10MHz OCXO divided down to 1Hz with a GPS PPS signal, the
effective VCO gain (Ko/N) is likely to be around 6E-7 rad/s/V (eg HP10811A) and
the phase detector gain around 1V/rad. Consequently a PLL loop bandwidth of
100uHz only requires an Integrator time constant of around 100 sec or so for a
second order PLL with an active PI filter. The required integrator time
constant can be reduced further by using an attenuator between the filter
output and the OCXO EFC input.
Bruce
On Wednesday, 25 May 2016 9:00 AM, Wes <[email protected]> wrote:
A cleaver design, but the OP wanted 1pps. I have the Leo Bodnar GPSDO. It
too
is a nice frequency standard, but it doesn't know what time it is.
On 5/24/2016 9:53 AM, Graham / KE9H wrote:
> If you want an "existence proof" for a simple, mostly analog, a few digital
> counters, no software or microprocessor GPSDO, look at the "Miller" GPSDO..
> He designed it for his own use, then put it into production because of
> demand for a simple, cheap GPSDO. It has been characterized, and works
> well for the simple circuit.
>
> The schematics are published, since it started as a hobby project.
>
> http://www.jrmiller.demon.co.uk/projects/ministd/frqstd0.htm
>
> http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm
>
> You can buy his, or build your own with his design as a starting point.
>
> He does use a GPS with 10 kHz output to simplify some of the timing and
> integration issues Bob referred to.
>
> --- Graham
>
> ==
>
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