Hi

Don’t get me wrong here, I think the SR620 is a great counter. My concern is that the
design came out a long time ago in terms of solid state generations. If things work out
as they often do, some random part in there is going to go obsolete. What part and when,
I have no idea. HP has always suffered from this when they shut down their custom
IC production on this or that. I don’t know of anything custom in the 620 so it is sort of
a race to the end ….. My concern is going to the boss a year from now and having to
explain that the super counter is now EOL ….

Bob

The FS740 is interesting. Obviously it has a lot going for it, but what appears to be missing is graphic data display capabilities which would simply be a few line of code. Perhaps I missed something skimming through the manual.

And it appears to be a simple L1 receiver, I myself am looking forward to an instrument with these great user features backed up in an instrument using L1/L2 as well as the other GNSS constellations with carrier phase as well is simply looking at the L1 timing signal. What I also find interesting is the rubidium has the same phase noise spec as their physically impressive stand alone quartz The phase noise is very good compared to LPRO and X72 on the FS725's I have measured  with the 5MHz phase noise meeting their specs but the 10MHz seems consistently about 10dB optimistic.

All and All a real nice instrument that may soon find a place in my lab. Tramsmille has also come out recently with a similar concept but I have not seen any details.

Cheers;

Thomas Knox

From: time-nuts time-nuts-bounces@febo.com on behalf of Magnus Danielson magnus@rubidium.dyndns.org
Sent: Saturday, November 11, 2017 8:57 AM
To: time-nuts@febo.com
Cc: magnus@rubidium.se
Subject: Re: [time-nuts] Favorite counters (current production)?

Hi,

On 11/11/2017 01:44 PM, Tom Van Baak wrote:

This is a common problem to the researchers and the time-nuts.
We can hope that the vendors reading this take notice about these needs.

FS740 GPS Time and Frequency Systemhttp://www.thinksrs.com/downloads/PDFs/Manuals/FS740m.pdf
www.thinksrs.com
Stanford Research Systems FS740 GPS Time and Frequency System Certification Stanford Research Systems certifies that this product met its published specifications at ...

Frequency Standards - Stanford Research Systemshttp://www.thinksrs.com/downloads/PDFs/Catalog/FS740c.pdf
www.thinksrs.com
Stanford Research Systems phone (40)744-9040 www.thinSRS.com Frequency Standards FS740 — GPS Time and Frequency System

Many thanks for this one, I did not know about this one, but look very
interesting.

Exactly my view. That we comment on it here, is since we learn and need
to track it. Hopefully they learn from this.

Vendors have become better at interacting again.

In the meanwhile, I hope Santa has a nice FS740 for me under the
christmas tree. Need to be nice now for a the rest of the year.

Cheers,
Magnus

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and follow the instructions there.

I (my company) have one of these.  Can you say more?

re: SRS, I ran into the CEO -- I have forgotten his name and misplaced his
card -- at a local office supply store in Mountain View near the end of
2016.  I was behind him in a long'ish xmas line.    He was buying some
end-of-the-year payroll forms.  He was with his wife, and he or she said
something that made me realize that he was with SRS.  So I introduced
myself first as an engineer at a local tech company that knew of his
company and then as a time-nut (never lead with the time-nut thing :-)).  I
explained that I had a couple of SRS rubidium standards, and  that there
were a bunch of folks in our pro-to-hobby community who really liked the
SR620.  (Would you please offer me a xmas discount on an SR620, please, I
did not ask.)  Really nice guy.  SRS is a small company -- we chatted
about some of the challenges they faced.  I related that I could remember
doing payroll paperwork by hand once upon a time.

-- Christopher.
73 de AI6KG

On Sat, Nov 11, 2017 at 2:42 AM, Tom Van Baak tvb@leapsecond.com wrote:

On Sat, 11 Nov 2017 04:44:53 -0800
"Tom Van Baak" tvb@LeapSecond.com wrote:

Oh.. very nice. I wasn't aware of this beauty!

I only had a quick look at the schematics, but a few things stick out:

1. They use "half" Nutt interpolators for time stamping instead of
   A-B measurements as is usual with the Nutt interpolator. I was wondering
   why nobody did that, as it is kind of the obvious thing to do, today.

2. They use simple, time-to-amplitude converter for the interpolation.
   The only interesting bit there, is the, in my opinion, weird way of
   starting the charge using an opamp, that at the same time compensates
   for the diode forward voltage.

3. This is the first time I have ever seen someone even mentioning
   the possibility of metastability in counters or the Nutt interpolator.
   And they solve it in a quite interesting way too.

4. Even though they call it TCXO in the manual, the normal oscillator
   in the FS740 is an ovenized AT cut crystal. As it is built manually
   on the main PCB itself, it's nothing fancy, but apparently does the
   job quite well.

5. Every other clock source in the instrument is derived from the 20MHz
   that this central oscillator produces. Even the 12MHz of the frontpanel
   controller.

6. The OCXO and Rb options only phase lock the central oscillator with
   a small PLL at 300Hz BW. That explains that the phase noise performance
   is constant over all 3 options. Though I would have expected a higher
   close in phase noise for the rubidium, as it does in the ADEV plot.

7. The Rb only performs slightly better between taus of 100 to 10k
   than the OCXO.

I probably have to spend some time reading the schematics, which by the
way are superb. So much love to details, even small ones. You can almost
feel what kind of trade-offs the engineers made and for what reason.

		Attila Kinali

--
You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering.  -- The Doctor

On 10 November 2017 at 16:37, Bob Camp kb8tq@n1k.org wrote:

If I had to take a bet, I would say the SR620 will be supported longer.
Stanford Research seem to be selling the same products they have for
decades. I started my Ph.D. in about 1994, and bought what was a very new
product - the SR830 lock in amplifier.

http://www.thinksrs.com/products/SR810830.htm

23 years later, it is still a current product.

Stanford Research also sell a couple of LCR meters

http://www.thinksrs.com/products/SR715720.htm

The SR720 looks remarkably like the long obsolete HP E4925A LCR meter.

There's no doubt in my mind that Stanford Research sell their products much
longer than HP/Agilent/Keysight. Of course, that does mean Stanford
Research are using older technology.

I would add, when I have contacted Keysight about obsolete products they
have always been helpful. When I contacted Stanford Research to ask what
was the latest firmware for an SR620, I was ignored. They also ignored some
other email I sent them. So their support does not seem as good as
Keysight, but I assume, with persistence, one could get support on a
current product.

Dave

That reminds me, should anyone have a schematic for an SR 830 walking amplifier, can you please get in touch with me. I have one that keeps eating voltage regulators.

At 06:44 AM 11/11/2017, Tom Van Baak wrote:

I've sent a couple of emails to info@thinksrs.com with no reply yet.
If anyone has a sales contact at SRS, please pass it along.

--
newell  N5TNL