[time-nuts] HP 5316B External Reference

[Magnus Danielson]

Hi Wes,

On 2020-07-12 00:51, Wes wrote:
> As I understand it this counter has an external reference input that
> isn't used directly as the time base but injection locks the internal
> time base.  Does anyone here know how well this works. Is using a
> GPSDO as a reference a worthwhile accuracy improvement?

It was fairly easy to locate the operations and service manual for the
HP 5314A and 5314B and they both have the same input setup, which is a
"injection lock multiplier" which is switched in on case of external
reference.

So, rather than injection lock the crystal oscillator, another
oscillator is switched in which is more a LC-resonator that triggers on
the edge of input. It's crude but good enough for the counter.

Feeding it a proper frequency will help, but you want to first do
trimming to adjust the free-running frequency, which can be done using a
procedure described in the manual that forces is into self-oscillation
so that it can be trimmed. Then, injection locking will pull it
sufficiently close.

It's crude but it works. This is not the counter they invested most in,
but it can still do quite a bit. It's a budget counter with ext ref and
HPIB. I have a 5314A which has neither of these, but may be suitable for
portable use or even battery use.

Cheers,
Magnus