[time-nuts] Reference input on HP counters

paul swed paulswedb at gmail.com
Sun Jan 7 10:46:38 EST 2018


Jerry
It depends on the unit and age. There are not rules of thumb from my
experiance.
Some of the approaches in HP as an example
Have switches and demand a specific frequency and level.
Some lock an internal reference to any multiple of a reference freq like 5
or 10 MHz.
Some are direct some are phased lock.
I actually look at each piece of HP gear and see whats going on.
Lazy can get you in trouble as I learned.
Regards
Paul
WB8TSL

On Sun, Jan 7, 2018 at 10:21 AM, Jerry Hancock <jerry at hanler.com> wrote:

> I’m being a little lazy as I can check the schematics, but in the general
> case, do HP counters, frequency generators, etc, switch to the external
> reference when one is available or discipline the internal oscillator?  Are
> there brands of test equipment that generally discipline vs switch?
>
> Third question, again generally, when you discipline an oscillator, what
> impact does this have on the oscillator's phase noise?  I assume this third
> question depends on the discipline loop (if I’m using the correct term).
>
> Thanks
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