[time-nuts] Cheap jitter measurements

Jeremy Nichols jn6wfo at gmail.com
Tue Apr 3 18:32:28 EDT 2018


On the practical side, the 5345 is HEAVY due to its older technology—doing
what it does with first-generation ICs required HP jam an enormous amount
of circuitry into a fairly small physical package.

Jeremy
N6WFO


On Tue, Apr 3, 2018 at 2:39 PM Bob kb8tq <kb8tq at n1k.org> wrote:

> Hi
>
> I would add the HP 5335 to the list of counters to look for. The surplus
> market can be really
> weird. A 5334 *should* be less than a 5335, but on any given day, that may
> not be true. The
> 5370 and 5345 are also worth looking for. Target price (at least for me)
> wold be < $150 for a
> quick buy and < $70 if I was willing to shop for a while.
>
> Getting data *out* of the older counters will involve GPIB. If you are not
> already set up to do
> that, there will be the cost of a cable and a simple adapter.
>
> If you want to move up a generation, the 53131 and 53132 are higher
> resolution devices than
> the 5334 and 5335. They give you the benefit of a serial port. No GPIB
> stuff to bother with.
> Finding one at price lower than the TAPR counter …. probably not.
>
> Bob
>
> > On Apr 3, 2018, at 3:04 PM, Tom Van Baak <tvb at leapsecond.com> wrote:
> >
> > Hi Gary,
> >
> > One solution is to look for used hp, Fluke, or Racal time interval
> counters on eBay. 1 or 2 ns is pretty easy to find with a $100 or $200
> budget. Look for Racal 1992 or hp 5334B as examples. If you plan to collect
> lots of data, you'll want GPIB (or RS232 / USB) connections to a PC and
> that will add to your net cost.
> >
> > Another solution is to homebrew your own 1 ns counter. The downside is
> you will spend a month working out the bugs before you trust the data. Plus
> if you don't already have another counter to compare it against it makes
> development even harder.
> >
> > Third solution is the TICC from TAPR. It's new and works out of the box.
> Lots of us use them. John did a very good job with the design. Highly
> recommended. It's a dual-channel *time stamping* counter so you can collect
> 1PPS data on two separate GPS receivers at the same time if you want. In
> that respect it's 2x as useful as a commercial *time interval* counter.
> >
> > You mention jitter, not ADEV. I don't think you need a fancy timebase if
> all you want to measure is jitter. You can get a good feel for the jitter
> of a GPS / 1PPS output within a few samples. Even a minute of data is
> usually enough to establish the rms jitter value. If you want a full ADEV
> plot, then yes, you'd probably want at least an Rb for your reference.
> >
> > See paragraph "Timing Stability" at http://leapsecond.com/pages/MG1613S/
> for an example of what jitter from a GPS receiver looks like; in this case
> it's primarily sawtooth.
> >
> > Right, the picPET has 400 ns resolution and so it is not the right tool
> for your nanosecond needs. I do have a 10 ns version that I use, but that's
> still a bit coarse for GPS work.
> >
> > I have spare FEI Rb here; I'll send it if you want it. That way you can
> afford a TICC.
> >
> > /tvb
> >
> >
> > ----- Original Message -----
> > From: "Gary E. Miller" <gem at rellim.com>
> > To: "time-nuts" <time-nuts at febo.com>
> > Sent: Tuesday, April 03, 2018 10:47 AM
> > Subject: [time-nuts] Cheap jitter measurements
> >
> >
> > Time-nuts!
> >
> > With care I can measure GPS jitter on a RasPi to a bit over 300 nano sec
> > resolution.  That is the smallest increment of the RasPi 3B clock with
> > a 64-bit kernel.  That is clearly not time-nuts accuracy.
> >
> > What would you guys suggest as the cheapest way to see jitter down to
> > around 1 nano second?
> >
> > I'm thinking maybe something like a rubidium standard (FE-5680A) and
> > a TICC-TAPR?  But that would put me out around $400.
> >
> > The picPET does not look accurate enough.  Maybe a clever way to use it
> > for more accuracy?  Is there a picPET like thing cheaper than the
> > TICC-TAPR?
> >
> > Ideas?
> >
> > RGDS
> > GARY
> >
> ---------------------------------------------------------------------------
> > Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
> > gem at rellim.com  Tel:+1 541 382 8588
> >
> >    Veritas liberabit vos. -- Quid est veritas?
> >    "If you can’t measure it, you can’t improve it." - Lord Kelvin
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