No MIT here.  Sadly.

Sent from mobile

On Dec 4, 2012, at 8:49 AM, paul swed paulswedb@gmail.com wrote:

Hi

Vacuum stuff sells by the pound (more or less). The kind you need in this
case isn't the cheap stuff. Pounds go up by the cube of the size. In this
case, I believe you want the fountain portion of the gizmo to be fairly
small.

Bob

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of paul swed
Sent: Tuesday, December 04, 2012 9:49 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] PTTI 2012, part 2

Basements the key. So for me bigger is better. Heck if its a rack thats ok.
It gets interesting in what types of components you can use if you are
willing to go larger.
Great point on the laser and optics. Funny thing is for small change you
can actually get used optics bench components at least at the last MIT flea
I ran across the items. They were snapped up by the way.

all that sure its beyond this group.
Regards
Paul

On Tue, Dec 4, 2012 at 9:34 AM, Bob Camp lists@rtty.us wrote:

can

rate)

probably

incompetence.

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To unsubscribe, go to
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and follow the instructions there.

The lasers arent that difficult to make or expensive if one adopts a
modified Littrow ECDL configuration.
Laser diodes without AR coatings have been used successfully in such lasers.
Low noise current sources and close temperature control of the laser
diode chip are required.

Bruce

paul swed wrote:

In message 50BE4F1D.7020702@xtra.co.nz, Bruce Griffiths writes:

Wouldn't the right way to be to do an optical comb, use that to lock
the lasers for the fountain, then lock the optical comb to the fountain ?

(Yes, I know! :-)

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

I agree, Bill. I do have some elk in the front yard, but they are no
help...
Don L
Bill Dailey

--
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
De Erroribus Medicorum, R. Bacon, 13th century.
"If you don't know what it is, don't poke it."
Ghost in the Shell

Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
www.lightningforensics.com
www.sixmilesystems.com

Hi

A few kilometers of optical fiber should do the trick. Servo the fiber temperature to keep things locked up.

Bob

On Dec 4, 2012, at 4:17 PM, Poul-Henning Kamp phk@phk.freebsd.dk wrote:

Hi

My 8th grade science project was made from optical bits from the MIT flea. One of the criticism's of the project was that it could have been better if I'd just shopped a bit harder….

What ever it is you need - it'll be gone when you need it.

Bob

On Dec 4, 2012, at 10:05 AM, Bill Dailey docdailey@gmail.com wrote:

Hi

But would you cryo cool the walls of the fountain enclosure? It helps …..

Bob

On Dec 4, 2012, at 9:46 AM, Bill Dailey docdailey@gmail.com wrote:

And here's the third part of my PTTI report...

• Vendor presentations/Symmetricom/Miles

Besides 3 days of presentations, PTTI also hosts a vendor/exhibit area. This includes the usual T&F suspects like FEI, Symmetricom, TRAK, Spectracom, SpectraDynamics, TimeTech, etc. Most of this gear is outside the budget of a regular time-nut but it's always nice to see and touch what's on display, knowing in ten years it will show up on eBay.

Yes, that was John Miles in the Symmetricom booth showing off his, I mean, their new TimePod and wearing a Symmetricom shirt. We've had a number of time nut "graduates" over the years: Rick Hambly went on to start CNS Systems, Said Jackson started Jackson Labs, John Miles became Miles LLC and both have ties with Symmetricom. You'll see press releases like this one:
http://www.gpsworld.com/symmetricom-expands-test-set-portfolio-with-high-performance-test-probe

If you have more questions, I'm sure John will be happy to answer then on- or off- the list.

• M12/uBlox GPS board

It was very nice to see Tom Clark ("grandfather" of time-nuts) at PTTI; it was from his work at NASA with VLBI, masers, and Motorola Oncore GPS receivers that a number of us caught the precise time bug in the early 90's.

Many of you know him as the author of the often recommended paper "Critical Evaluation of the Motorola M12+ GPS Timing Receiver vs. the Master Clock at the United States Naval Observatory, Washington DC" which is available here:
http://www.gpstime.com/files/PTTI/PTTI_2002_CNS_Testbed.pdf
http://www.gpstime.com/files/PTTI/PTTI_2002_CNS_Testbed_VG.ppt

Anyway, this year Tom Clark presented performance results of a new GPS board. It is h/w and s/w compatible with the Motorola M12 receiver used in many existing T&F products, but it's based on a uBlox-6T chip instead of the Motorola or iLotus M12 chip. The trick is that Rick Hambly added a PIC on the board to make it talk exactly like an M12. The reason for this is to allow drop-in replacement of the original Motorola M12 or still-current iLotus M12+ with this new one. It's called the Synergy SSR-6T.

That means that any instrument (e.g., GPSDO) that uses an M12 can be upgraded to the uBlox-6T. Tom's presentation contains charts showing the performance improvement:
http://www.cnssys.com/files/PTTI/Low_cost_GPS-based_time_and_frequency_products.pdf
http://www.cnssys.com/publications.php

I have one to play with and hope to duplicate his results. I didn't get pricing/availability info but it is supposed to be "really cheap". (Tom Clark -- can you provide this info when you get it?)

• Quartz in space

With all the focus on fiber and optical and atomic clocks, it's refreshing to hear now and then about good old quartz. This was a fascinating talk about real-world (or real out-of-this-world) performance of quartz oscillators in space. What they did was mine recorded telemetry from many space missions looking to directly/indirectly measure the frequency of the quartz oscillator over years in space.

Just like we use LH to monitor the EFC of a GPSDO, they monitor the EFC of the quartz LO in the GPS sats. In addition to normal drift there are effects of radiation dose and solar flares. I'll post the URL of the paper when it's out. Meanwhile I saw a bunch of fine papers/presentations at the FEI site:
http://www.freqelec.com/tech_lit.html

• ION/PTTI 2013 in Bellevue, WA (!)

After 44 years, PTTI is changing "management". Instead of being organized by the US government (USNO, NASA, JPL, and DoD) it will now be run by ION (Institute of Navigation). This keeps the government out of the hospitality and conference business.

The next ION/PTTI will be held in Bellevue, WA. If you haven't considered attending an ION or PTTI conference before, this might be a good one to try. Also, since that's my hometown, I plan to have an "open house" during the conference. That means I have a year to clean up the lab so more than one person can walk in it...

A number of people continued to comment on the relativity experiment I did a few years ago. I have now posted the original (190 page) power-point presentation I gave at PTTI that year:
http://www.leapsecond.com/ptti2006/

• The state of Time-Nuts

Lastly, I wanted to make a note about time-nuts. I was pleasantly surprised how many professionals already know about the time-nuts list or lurk here. This group has really done well. Perhaps propelled by advances in the telecom/optical world or neutrino experiments, there's a whole new crop of scientists in the precise time field. Formal technical journal articles by PhD's tend not to deal with the mundane details of precise time measurement and lab equipment so people turn to google, and find us here.

As the list grows we face some issues about posting bandwidth, focus, and repetition. The list is mostly unmoderated, so it's completely up to you to keep the list relevant and interesting. Please resist too off-topic posts or low-content postings. For now at least, the archived list is rich enough that it acts like a wiki or faq.

As usual, if you have suggestions on how to make the list better please send them to me (tvb@LeapSecond.com) and John (jra@febo.com).

Thanks,
/tvb

Great comments and a good read. OK so what does the drop in replacement
cost???
Thanks lots to read here.
Later
Paul
WB8TSL

On Thu, Dec 6, 2012 at 10:24 AM, Tom Van Baak tvb@leapsecond.com wrote: