[time-nuts] Subject: Re: GPS 1PPS, phase lock vs frequency lock, design

[Glen English VK1XX]

Hi Bob

RRR.

In fact  all my original GPSDOs in the '90s were FLLs, for radio comms 
gear, essentially frequency counters with the error driving a PI loop. 
They were controlling standard XOs. For new engineers, if they want a 
project to teach them many skills, I recommend a GPSDO project from 
scratch, there are many excellent disclipines to grasp, oscillators, 
control systems, measurement.... and  many systematic errors to 
understand... and the project is only done if the spec is met, and of 
course the spec can go on being as tight as you want. You could spend 
your whole life on it.

glen
On 25/06/2019 1:16 PM, Bob kb8tq wrote:
> Hi
>
> In a GPSDO, an FLL can be done with no “cycle slips” between readings. In that case, the I term will indeed
> correct for long term errors. The net result will be effectively the same as a PLL for long term error. That is by
> no means to say that *all* FLL’s are done this way. Only that it is one possible implementation.
>
> Bob
>