[time-nuts] Just any counter external reference and discipline mode.

[jimlux]

On 7/13/20 11:27 AM, paul swed wrote:
> Taka
> I firmly believe the first answer to your question is cost.
> Was the counter an economical unit or higher quality.
> My 5335 counters have seriously cheap xtal clocks and an external reference
> makes a big difference.
> But the larger costly generators and counters seem to use the phase lock
> approach. I suspect it also filters the reference input.
> Regards
> Paul
> WB8TSL
> 



There's a lot of lore out there that, for instance, HP would put 
oscillators with good long term stability in counters, but for things 
like a spectrum analyzer or signal generator, you'd use an oscillator 
with good close in phase noise, because absolute frequency accuracy 
isn't as important, but ability to make close in measurements with high 
dynamic range is.

I would also not make any assumptions about continuity of design, 
especially when it changes from an all analog to a DDS based design. A 
synthesizer using analog synthesis with PLLs would smoothly sweep, while 
a DDS design typically goes in discrete steps (unless specifically 
designed for smooth sweeps), and may or may not be phase continuous 
across steps.