Re: [time-nuts] Good GPSDO on eBay?

[Dimitri.p]

since you asked ...
Many thoughts, none of them good.
Recycled components sold for real money.
Too many "versions" to figure out "what you got".
If all you want is a frequency standard to turn it on and "forget it" 
spend a few extra bucks and get one with all new components from a 
domestic company.

Or if you want to have some fun put together one of your own.



At 04:40 PM 7/9/2016, Richard Mogford wrote:

This looks like a good beginner's GPSDO on eBay: 172148560746

"This is GPS Disciplined Clock made with trimble GPSDO Board.Full 
tested by Agilent 53132A with US-012 option and Ex-ref from trimble 
thunderbolt GPSDO."



 The seller says it has a sine wave output and is accurate from
 10e-11 to 10e-12.

Any thoughts?

Richard

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Re: [time-nuts] Simple solution for disciplining OCXO with 1 PPS

[Dimitri.p]

Among Simple , analog, 1PPS
you'll have to pick two of the three.
The miller GPSDO needs 10KHz  it's simple and 
analog.  http://www.jrmiller.demon.co.uk/projects/ministd/frqstd0.htm


The IK0OTG is simple, uses 1PPS and is digital 
http://www.ik0otg.net/index.php?option=com_content=article=53%3Aoscillatore-10mhz-sinc-gps=34%3Ahome-made=59=en




At 10:41 AM 5/22/2016, Bernd Neubig wrote:

Hello Fellow time-nuts,
I am looking for a simple solution to discipline my 10 MHz reference 
OCXO in my private lab with an 1 PPS signal from a separate GPS receiver.
I am curious if there is a solution possible without programming a 
microcontroller, as I am an old-fashioned "analogue" guy ;)
I am well aware, that such a solution would have a lot of 
disadvantages, as it cannot effectively compensate for short-term 
variations. However I would be happy if such a KISS solution could 
achieve  a stability (STS) of better 1E-10 over an hour. I know this 
is a damned long integration time for an analogue integrator...
If that sounds too weird, I am open to receive advises for a 
microcontroller based solution.


Thanks a lot for your comments to come.
BTW: you need not to teach me about basics of short-term stability. 
I just want to evaluate the limits of a possible analogue solution. 
For sure, that's not real disciplining, but more like a long-tau 
integration PLL


Best regards
Bernd DK1AG

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Re: [time-nuts] Cheap LEA-6T [was: Re: Precise Time transfer and relative position over ashort baseline]

[Dimitri.p]

They are using LEA-6T0-000
My 6T-0-000 reports
Software version 6.02(36023) and hardware version 00040007 in the UBX 
MON (Monitor) VER (Version)


In the datasheet there is no 6T0-0-000  but there is a 6T-2-000 with 6.2 FW.
LEA-6T
LEA-6T-0-001  ROM7.03
LEA-6T-1-001  FW7.03
LEA-6T-2-000  FW6.02

But not bad for less than 30 bucks

Dimitri



At 02:26 PM 4/12/2016, Attila Kinali wrote:

On Mon, 11 Apr 2016 13:47:36 -0500
Scott Newell  wrote:

> BTW, there are some LEA-6T modules (with patch antenna, compass, 1PPS
> led, and USB connector) intended for drone autopilot use on eBay for
> around $30 shipped from China. (Search for "LEA-6T".) Mine showed up
> on the day of my lightning strike, so I've barely played with it. It
> has the 6.something ROM, connects to u-center, and appears to output
> the +/-10 ns sawtooth error correction message and the RTKLIB
> compatible raw data.

There is something strange with these. For one thing, they are way too
cheap. LEA-6T is still quite expensive when bought from u-blox directly,
eventhough it came down from 180eur/pcs to 140eur. The prices these
modules are selling are lower than the cheapest price i've ever seen
for LEA-6T's, when bought in the 100s. So, either they bought them in
swats of 10k or there is something amis...

Also, why would anyone use LEA-6T in navigation module? That does
not make sense. The power of the LEA-6T is as a timing module, not
for navigation.

And last, but not least, the pictures seem wrong. All the LEA modules
i've seen, had two shield covers, one over the RF part and one over
the digital part. Yet these shown in the pictures have only a single
shiled. It might be that u-blox decided to use a single shield
for them... though it would seem strange to do that to an already launched
product that sells in relatively low volumes. Even more so, as I know
that u-blox itself warned users of their modules to ensure an electrically
quite enviornment around their modules, for maximum performance.


So, i would warn people buying those that they might be fakes...


Attila Kinali
--
Reading can seriously damage your ignorance.
-- unknown
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Re: [time-nuts] Advise on building a DIY GPSDO?

[Dimitri.p]

Miller GPSDO vs HP Z3801A,  Jackson Labs Fury GPSDO,  vs Trimble 
Thunderbolt  compared Feb 2008


http://leapsecond.com/pages/gpsdo

It seems the Miller GPSDO, for an "unlikely" design, it can hold its 
own pretty good.




At 06:56 PM 4/4/2016, you wrote:

Don wrote:


5.  Design a voltage tracking / filter to match the OCXO
control requirements.
6.  And, ...ta-dah;
7.  You have a 10MHz, bench frequency standard that will
rival all others


Not very likely.  The whole point of a GPSDO is for the frequency to 
be controlled by the more stable source (OCXO or GPS) at all 
integration times (tau).  But the OCXO will typically be more stable 
than the GPS for tau less than several hundred seconds (see graph 
below -- black line is GPS, brown line is a typical OCXO).  So, the 
PLL needs to have a time constant of hundreds of seconds.  Such a 
PLL filter cannot practicably be designed in the analog domain, so 
one needs to design a digital filter with appropriate time constant 
and damping.  Because of the very long time constant, it is almost 
necessary for the filter to have more than one, switchable time 
constants to avoid extremely long lock times.


Very few home builders are capable of designing a proper digital 
filter suitable for this application (the counter-based loops of 
most published DIY GPSDO designs are not proper digital filters).


So, no -- it is very unlikely that a home-built GPSDO will "rival 
all comers," whether the builder designs his or her own circuit or 
uses one of the many published circuits.


Best regards,

Charles


Graph below.  Note that a properly designed GPSDO would show 
stability that follows the OCXO (brown line) at low tau, and the GPS 
(black line) above the point where they intersect -- here, about 350 
seconds.  Note that a loop filter with proper damping will NOT 
exhibit a "hump" near the crossover (many GPSDOs do exhibit a 
pronounced hump, betraying that their loop filters are not properly designed).




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Re: [time-nuts] Advise on building a DIY GPSDO?

[Dimitri.p]

Regarding "as good a place to start as any",  ublox receivers will do 
10KHz all day long.
I didn't realize ublox receivers have dual output until after I built 
a couple of other GPSDOs, (well, maybe four)


As for a good  OCXO: other than the Morion MV89a, ($20-$50)  for 
anything else, figure about one or two hundred bucks depending on new 
vs used and "luck".


But as it's been said before it all depends on if you are building 
"to use" or "to play/learn/experiment/get your hands dirty"


Building does not save money or time and buying doen't give you an 
excuse to fire up the soldering iron.

Decisions...decisions...


Dimitri.p


At 12:00 PM 4/4/2016, Chris Caudle wrote:

On Mon, April 4, 2016 11:18 am, Tom Holmes wrote:
> The preceding questions always come up when a newbie
> comes up on the list wanting to build their own GPSDO.

It is good to make sure the person actually wants to build a GPSDO.
A few years back I was in a similar position, and my answer was I actually
needed a high accuracy reference to check frequency accuracy of some
clocks, and the recommendation was just get a Thunderbolt.  I didn't know
about surplus GPSDO's available so that was good advice for me, I didn't
actually >want< to build a GPSDO myself.  It would have been fun, but the
end goal was more important to me.

So I think really the first question should be do you want to build a
GPSDO, or do you want a high accuracy time and frequency source for its
own use?  Because if you want to own a GPSDO to use, building one yourself
is probably not the way to go.  Get a surplus unit, or save up a little
more and get a new Jackson Labs.
If you just like to build stuff and a GPSDO is the particular stuff you
want to build next, then go ahead and have fun.  Chris Albertson's arduino
based design is probably as good a place to start as any, it should be
cheap and I think the pieces are easier to find than that CPLD based
design that relies on having a GPS that can output 10kHz instead of just
PPS.

--
Chris Caudle



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Re: [time-nuts] HP5370B & HP5345B Front-End IC Redesign Effort

[Dimitri.p]

Someday , someone will get bored with everything 
else and give it a try, you know, in their spare time.

The time when these counter were new was a long while ago.
Back then an amplifier chip with 500MHZ BW was a 
much bigger deal than it is in 2016.

...but spare time is permanently on backorder  :)

Dimitri

At 06:15 AM 1/24/2016, Bob Camp wrote:

Hi

Back when these counters (5345, 5370, 5335) all were new, the inputs were
the weak link on all of them. There were known 
“don’t do that” things on the line
that would blow out each of them. Regardless of 
the level of care and yelling, inputs

blew on a fairly regular basis. Probably 10% of the counters went back
for repair over a 5 year period. It was always a 
“swap out the entire board” sort
of repair and never was under $1K. We regularly 
spent the price of a new counter
each year on repairs. If there had been an easy 
way to fix them,  (or even to just

pay $500 for the chip) we would have done it.

Bob

> On Jan 24, 2016, at 8:34 AM, Dale Cannon  wrote:
>
> Funny,
>
> A friend asked me if I could replicate the front end for a 5370A, a many
> years back. I related to him that replicating the input chip was not a
> trivial task. His 5370A had been used (by someone else) for direct testing
> of controlled-motion DC motors and the front end had obviously been
> overstressed by voltage spiking. At the time, I had considered replicating
> the front-end probe circuit of a K100D logic analyzer: FET diff. pair
> followed by an ECL 10216 line driver. Obviously most daughterboard or dead
> bug modification approaches have downsides; in the end I just couldn't cut
> up the HP front end and told him to search for a more qualified repair
> facility.
>
> BAMA boat anchors has the K100D manual and probe schematic.
>
>   Dale Cannon  KS4FA
>
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Mathew
> Breton
> Sent: Friday, January 22, 2016 5:15 PM
> To: time-nuts@febo.com
> Subject: [time-nuts] HP5370B & HP5345B Front-End IC Redesign Effort
>
> I was gifted an HP 5370B with the usual problem: front-end problems,
> probably due to overstress. It is currently up and running again with a set
> of 5345A series A3/A4 boards as I wasn't able to get a cheap pair of
> 5088-706x hybrid ICs.
> This sounds like a common problem. As a 
result, I'm designing an open-source

> drop-in (hopefully) replacement. My hat is off to the original IC designer,
> as it is not a trivial effort due to the wide input signal common-mode
> range, and very tight trigger timing requirements. Other items (like the
> E-ECL) output) are also adding a bit of extra effort.
> I'm hoping that someone(s) might be interested in working with me on it. I
> would like to have my assumptions and math checked before I start the
> detailed design phase, and perhaps contribute some better ideas.
> In addition, it would be really helpful if 
someone could run a few rise-time

> dispersion tests on an instrument with a working "B"-series A3/A4 PCB set
> (my unit obviously doesn't qualify).
> Regards,
> Mat Breton
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Re: [time-nuts] 10811 unsoldered fuse

[Dimitri.p]

Are they visible from the same side as the 
thermal fuse and the IC or are they under the 
board  so you can only see them once you start taking the boards apart ?


Thanks,
Dimitri


At 11:48 PM 10/23/2015, Luca Dal Passo wrote:

Hi all,
   i have on my desk a disassembled 10811 for service. It has a thermal
fuse of the rectangular black type placed just above the IC. The leads are
plugged into two very small sockets on the pcb, they are not soldered.
Bye
Luca
iw2Lje



Il giovedì 22 ottobre 2015, J. L. Trantham <jlt...@att.net> ha scritto:

> David,
>
> Good to know.  Thanks for the info.  Any idea of a source for that part?
>
> I don't remember whether my fuse was soldered in or plugged in.  Whatever
> it was, I replaced it the same way.
>
> Thanks again.
>
> Joe
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com <javascript:;>] On
> Behalf Of David G. McGaw
> Sent: Wednesday, October 21, 2015 10:02 AM
> To: Discussion of precise time and frequency measurement
> Subject: [Bulk] Re: [time-nuts] [Bulk] 10811 unsoldered fuse
>
> That probably is an original thermal cutout.  It matches ones I have found
> when repairing 10811As.
>
> David
>
>
> On 10/20/15 7:59 AM, J. L. Trantham wrote:
> > Dimitri,
> >
> > That clearly is not the 'original' thermal fuse that I found in my 10811.
> > Mine was a small, axial lead, cylindrical part.
> >
> > It looks like someone substituted a different part (is that a fuse or
> > a
> > cutoff?) and did a poor job soldering.  I think the temperature is
> > correct though.  I'd have to look at the manual to know for sure.
> >
> > My 'fuse' failed and I replaced it.  All the soldering was OK on my unit.
> >
> > Joe
> >
> > -Original Message-
> > From: time-nuts [mailto:time-nuts-boun...@febo.com <javascript:;>] On
> Behalf Of
> > Dimitri.p
> > Sent: Monday, October 19, 2015 2:32 PM
> > To: time-nuts@febo.com <javascript:;>
> > Subject: [Bulk] [time-nuts] 10811 unsoldered fuse
> >
> > How common is it to find undetected missing solder on 10811 parts
> > after all these years?
> >
> > Dimitri
> >
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Re: [time-nuts] Unified VCXO Carrier Board

[Dimitri.p]

The price of the resistors is small change 
compared to the $8 connector for the 10811.
Then again maybe the plan is not to actually 
build one board with all the parts that will 
accomodate any of the OCXOs on the list



Dimitri

At 04:44 AM 10/22/2015, Bob Camp wrote:
> 2. It provides unified tuning: 0V = lowest 
possible frequency, 3V3 or 5V = highest 
possible frequency, no matter of the VCXO tuning sense and range.


That immediately gets you into op amps and 
feedback resistor stability. With a number of 
combinations, the required resistors can get pretty expensive. It

also gets you into dual supplies with some OCXO’s.


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Re: [time-nuts] 10811 unsoldered fuse

[Dimitri.p]

From the top side of the board I couldnt' tell if what looks like an 
unsoldered joint was supposed to be a single pin, so I soldered the 
leads  and have been enjoying it working.
If it acts up again I'll take it further apart to see what's on the 
other side.


Thanks for all the replies.

Dimitri



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Re: [time-nuts] GPS Referenced Programmable Oscillator...

[Dimitri.p]

It would be interesting if the programmable PLL 
was offered as a stand alone (using an external 
10MHZ reference) ..now that would be something.

Instead of adding a mystery GPS receiver and a mystery TCXO into the works.
Most people interested on this probably already 
have one or two (or more ) GPSDOs  :)


Dimitri



At 10:34 PM 10/18/2015, Bob Albert via time-nuts wrote:
Well it seems to me to have too high a 
price.  It could be useful; if I had one I'd 
use it as a master oscillator for my HP 
counter.  My ham transceiver is very accurate 
so I don't need to improve on it.

If it were around $50 I would be very interested.
Bob K6DDX



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