Thank you for the interesting information. Now, the time has come to
look for an adequate counter - anyone who has experience with the HP
53132A and the SR620? If they both where at - say 1000 USD - what would
you prefer for the job of phase measurement? I've read about that
massive single shot capability of the SR, but - as being a newbie - is
there anything I overlook at this moment?

Thanks

Volker - DF9PL

Am 02.11.2012 16:32, schrieb Volker Esper:

On 11/03/2012 03:10 PM, Volker Esper wrote:

For short time-scales, single shot resolution and trigger jitter
dominates your measurement floor.

Single-shot resolution is the time resolution by which you make a single
measurement.

Trigger jitter is the noise at the trigger point. it's a combination of
thermal noise and the slew-rate at the trigger points. It is often that
trigger jitter is dominated by slew-rate, but there is also internal
sources of trigger jitter. The slope dependent trigger jitter follows
the formula:

t_jitter = v_noise / s_slew

t_jitter is the trigger jitter (s)
v_noise is the noise power (V)
s_slew is the slew rate (V/s)

When the time-span of a measurement is long, long-term stability comes
in as well as systematic drifts. Also, systematic noise such as hum also
becomes important.

To see how much you depend on slew-rate limitation, you can reduce the
amplitude, and as this reduces the slew-rate you can separate the
slew-rate dependent jitter from the intrinsic jitter of the input. It
also helps you to identify if you need to work on the slew-rate limit
rather than anything else.

So, it may not be the single-shot resolution which limits you, but a
combination of things.

I would recommend you to pick up a SR620. It has 4 ps single shot
resolution and about 25 ps jitter (but you can get less). That is
significantly better than the 53152A provides.

SR620 manual (one of many links):
http://ilrs.gsfc.nasa.gov/docs/timing/sr620_manual.pdf

Cheers,
Magnus

Hi Magnus;
I hope this is not to far off thread. Has anyone in the group done real world measurements of single shot res, and jitter on the new Agilent and Tektronix/Pendulum counters compared to the SR620 and Agilent 53132A. I would imagine that counter designs would be an area that really benefits from ongoing advances in digital technology.  I have also found that it is much easier to claim specs then meet specs.
Thanks;
Thomas Knox

Hi

Both counters have their weak points long term. On the balance I think the 620 should last longer. The 620 is the higher resolution of the two. The 620 normally comes with a bit better reference. Both are supported by various Time Nut software packages. Both do GPIB and serial i/o. The 620 is a bit more controllable over serial. The 53132 takes up less space on your bench.

For the same price - go for the 620. For the usual 53132 is $1300 and the 620 is $2400, not so clear.

Bob

On Nov 3, 2012, at 10:10 AM, Volker Esper ailer2@t-online.de wrote:

Hi

The 620 is still pretty good (when tuned up). It certainly beats the Pendulum's on a single shot basis. The 53230 is spec'd to be as good as the 620. I suspect it meets or exceeds it's stated specs.

Bob

On Nov 3, 2012, at 12:58 PM, Tom Knox actast@hotmail.com wrote:

Hi Tom,

On 11/03/2012 05:58 PM, Tom Knox wrote:

I haven't tested the new 53230 counter, and not the CNT-91/PM-6691
counter either, but much of the others.

It should not be too hard to test this. I have made some tests with the
aggregate of single-shot and trigger noise on a sine signal, i.e. 5 MHz
out of a BVA. It gave the expected separation as a linear slope on the
ADEV. On the other hand just tossing a sine into counters isn't
necessary the most fair comparison, so in that sense it just gave a
rough image.

This thread have again had me consider reviving the testing aspect, and
I decided to get a 53132A counter finally, now that prices have gone down.

Cheers,
Magnus

Hi Bob

I didn't expect something to be tunable in the counter (except for the
oscillator) - what is it that has to be calibrated?

Thanks

Volker

Am 03.11.2012 18:04, schrieb Bob Camp:

Hi

There is a fairly elaborate alignment procedure for the 620. It's been reported in great detail here on the list. The counter definitely does better after you go through the full process.

Bob

On Nov 3, 2012, at 3:42 PM, Volker Esper ailer2@t-online.de wrote:

Hi Bob

What is it, that limits a counters life, are you speaking of typical
counter specific failures or do you just mean the common wearout?

Sorry, I know those are no smart questions - but my heart is thumping
when I think of the price and the long way it has to go over the sea...

Thanks

Volker

Am 03.11.2012 17:59, schrieb Bob Camp:

Hi

In the case of the 53132, the power supply seems to be the weak link. Out of maybe a hundred or so in the fleet, we see maybe one or two die each month. On the SR620 the power supply also seems to go from time to time. Both have the normal keyboard and display issues, but those can be fixed. If you go back to things like the 5335, the weak point is the input amp, it blows if you get +5 on it. Like power transformers - not a replaceable item...

Bob

On Nov 3, 2012, at 4:10 PM, Volker Esper ailer2@t-online.de wrote:

Ah, ok, that helps. Meanwhile, I've found the manual and the schematics,
and it seems to be possible, to get a died power supply back running.

Thanks a lot!

Volker

Am 03.11.2012 21:36, schrieb Bob Camp:

Great, your answere gives me hope, that the calibration procedure can be
done at my home :-)

Thank you!

Volker

Am 03.11.2012 21:08, schrieb Bob Camp:

Folks,

Given that slew rate is so critical, why do we distribute sine waves and
perform the zero-crossing detection at every target instrument?

david

On 11/03/2012 09:36 PM, Bob Camp wrote:

Another weak point on the 5335 is the relay. We had to replace it and
the relay-holder, but once that was done, it was back up operational.
The 5335 ticks in as the most human-friendly of the counters at work,
while the 53132 is competing with the 5372 as being the most
human-unfriendly, where the 5372 has more capabilities to present, so it
gets used more.

Cheers,
Magnus

David,

On 11/03/2012 10:44 PM, David Hooke wrote:

... or rather, why do we design our input stages so they are so
slew-rate sensitive?

Sine isn't necessary a bad choice, the benefit of a sine is that you
would not have to be as wide-band as to handle a whole number of
overtones. That translates into lower amount of noise.

There isn't really one right way of doing it, you can go about it in
several ways, but you need to do it consistently.

I've modified my TADD-2:s such that I use the input treatment to drive
one of the outputs, so that they will square up sines for me. For some
signals this have lowered my trigger jitter and hence improved my
ability to see more of the actual signal I want to see.

Just as much as you can get a counter with very high single shot
resolution, it doesn't help if you do not treat your signals properly to
get the most of that counter.

When doing DMTD tricks, the mixer is the easy part, squaring the signal
up to get good trigger jitter for the total is what takes a lot of effort.

Cheers,
Magnus

Usually you don't need a BVA to test the single-shot capability of a
counter: a length (say 50nS) of good RF coaxial cable and your preferred
OCXO/Rb/GPSDO should be enough.

On Sat, Nov 3, 2012 at 11:14 PM, Magnus Danielson <
magnus@rubidium.dyndns.org> wrote:

Hi

If you have a sine wave, it gets into everything. You can identify it and take it out of your data.

If you have a broad band uber-fast high level pules, it gets into everything. Identifying it's impact and taking it out of the data - not so easy.

That may sound a bit crazy. I've actually worked in a place that went over to a square wave based system. It lasted for about a day. Got into all sorts of things, total nightmare.

Bob

On Nov 3, 2012, at 5:44 PM, David Hooke dhooke@gmail.com wrote:

Hi

The relay can be replaced. Not so much with the input amp. If it goes, you lost the counter. The displays also die from time to time. Like the relay, they can be replaced.

Bob

On Nov 3, 2012, at 6:14 PM, Magnus Danielson magnus@rubidium.dyndns.org wrote:

david wrote:

Magnus made some good points in response to your question. To
elaborate a bit: it is much easier to provide a friendly transmission
environment for a sine wave (single frequency), and sine waves are
less sensitive to imperfections in the transmission environment
(impedance discontinuities and mismatches, noise ingress,
etc.).  Reflections in the transmission environment will put funny
steps in what started life as clean square waves or pulses, and
differential phase shifts will also mis-shape square waves or
pulses.  This can even be a problem with sine waves -- see, for
example, the NIST paper on the timing effects of distortion in sine
wave sources for an example of the sensitivity of sine wave systems
to harmonics (Walls and Ascarrunz, The Effect of Harmonic Distortion
on Phase Errors in Frequency Distribution and Synthesis) -- but it is
much worse with square waves or pulses.

Sine wave systems are also much less prone to radiating
noise.  Anyone who operates one or more frequency standards as well
as sensitive RF receivers can testify that sine waves are much less
of a hassle.

Best regards,

Charles

The below is correct but a simpler way to say it is this:

"A square wave contains the fundamental frequency plus every odd harmonic
up to infinity.  A sine wave contains only the fundamental frequency."

It is the "up to infinity" part that causes all the trouble.  And yes it
really does go to infinity, at least in theory.  but in real life you can't
have frequencies so high so without them you can't and don't have a perfect
square wave.  In other words perfect square wave can't esist in the real
world but perfect sine wave, at least in theory could

On Sat, Nov 3, 2012 at 4:39 PM, Charles P. Steinmetz <
charles_steinmetz@lavabit.com> wrote:

--

Chris Albertson
Redondo Beach, California

Of course you can't have a perfect square wave!  That would imply zero
transition time and since frequency is inverse to time that implies infinitely
high frequency bandwidth is required to achieve that perfect square wave.
Getting a "square" wave with a "fast enough" slew rate between high and low
levels is certainly achievable and better than that perfect square wave.  Be
careful what you ask for, because with a perfect square wave you would have such
high frequency content that you would get induced noise everywhere.

Peter

On 11/3/2012 8:05 PM, Chris Albertson wrote:

On 11/04/2012 01:13 AM, Peter Gottlieb wrote:

... oh, THAT would be useful! :D No trigger point jitter!

... and it would be a hell to contain within the cables and connectors
we have, as they leak a lot as you get up into frequency.

Indeed. Bob has shown this.

Another aspect of it is that phase-shifts at higher frequencies may eat
into the phase shift of the zero transition, so it may for some systems
give a worse environmental/temperature dependence than a sine would.

Then again, if you check your signal properly, a square-wave may be
exactly what you want and need. It's just that again, your milage may vary.

Cheers,
Magnus

Hi

If you slew rate limit the square wave (which is reality) you get a sin(x)/x frequency response. It doesn't go to infinity, but the lobes keep going for quite a while.

Things like cables and connectors have upper frequency limits as well. A square wave will only be happy with a linear phase shift. Both cables and connectors depart from a linear phase vs frequency response if you go high enough in frequency. Some get quite nasty. The original Heliax with the constant spacing in the inner supports was really crazy when hit with a fast pulse. It pretty much rang forever and ever…

A simple square wave implies a DC level for a switch point. With long runs that gets messy. Most practical systems go differential. You double the cable cost, but get back to a simple switch point.

No free lunch.

Bob

On Nov 3, 2012, at 8:46 PM, Magnus Danielson magnus@rubidium.dyndns.org wrote: