[time-nuts] GPS jamming test in SW US this month.

[Ryan Stasel]

Interesting article linked off slashdot. Apparently the Navy will be doing some 
GPS jamming experiments. Would imagine it could cause some GPSDO drift

http://m.slashdot.org/story/312173

Ryan Stasel
IT Operations Manager, SOJC
University of Oregon

Sent from my iPhone
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Re: [time-nuts] Transformer inrush current and transformer simulation

[Mike Monett]

> OnFri,03   Jun   2016   12:37:26   -0400"Mike  Monett"
>  wrote:

>> I found  a  significant  error in  the  LTspice  analysis.  I was
>> wondering how the current could jump instantaneously at zero when
>> the voltage is applied at the peak. That violates magnetism.

>> It turns  out  it doesn't. When LTspice  starts  an  analysis, it
>> first calculates the operating point. For the Sine voltage source
>> at 90  degrees, it applies the full voltage across  the  load. In
>> this case, it was 169.7V across 1 ohm, resulting in 169.7 Amps.

>> That is what was plotted, and is a significant error.

> Actually, spice  (the  engine behind LTspice) does  a  DC analysis
> before almost  all  modes of operation. This DC  analysis  has the
> intention to start the circuit from a steady-state point  and thus
> to reduce simulation time. In order for this to work properly, you
> have to  specify  the  DC voltage  and  currents  for  all sources
> correctly. Spice messes this up at times making the first  part of
> a transient simulation worthless (it has even worse  problems when
> you do  an  AC analysis). Additionally LTspice hides  too  much of
> these small  complications for the problems to be  visible  to the
> untrained eye  and  also at times makes it harder  to  provide the
> correct values. Thus, caution is advised.

After starting  with Intusoft in 1985, moving to  Microcap  in 1991,
having a  brief  fling  with PSpice around  1998,  and  switching to
LTspice in 2006, I can say LTspice has the easiest and  fastest data
entry of any SPICE program I have tried.

There is no problem with specifying the sources in  LTspice. Nothing
is hidden.  The  setup   menus   are   extremely  easy  to  view and
understand. If you wish, you can have the input parameters displayed
on screen, as I have done with two of the functions.

LTspice checks all the information given, and if it detects an error
it generates an error message and won't run.

My original  problem  was not the setup menus.  It  was  picking the
wrong model.

> The general  rule of "Never trust a simulation you  haven't forged
> yourself" applies.

Most people would be hard put to do a hand simulation of  a wideband
op amp in a closed-loop feedback network. That is what SPICE is for.

>> Out of  13  examples I analyzed, I found only  one  that involves
>> unloaded transformers.

>> I found  many references that discuss transformer  inrush current
>> caused by  core saturation. This is a serious problem as  it puts
>> stress on the components and reduces operating life.

> I only  had a quick glance at your webpage, but it seems  that you
> used the  standard LTspice transformer model.  Unfortunately, this
> is not a good model to study this kind of behaviour. For  one, the
> only loss  considered  in the model is  the  winding  coupling, it
> doesn't even directly consider resistive losses in the windings.

You would  be advised to learn LTspice as it would save you  a great
deal of misconceptions about how it works.

The winding  resistances  are included in  the  inductor  model. You
specify them as needed. I usually used a series resistance of 1 Ohm,
but changed  it  in some examples to suit the  application.  You can
also specify the parallel winding capacitance and resistance.

> In this  case,  the two most important effects  that  you  need to
> include are  saturation and core losses, which are  both frequency
> dependent. The  cores  of electric machine  transformers  are very
> poor when it comes to their "high" frequency behaviour. Where high
> frequency starts somewhere closely above mains frequency.  Ie 1kHz
> is already  so  far off that somewhere around  90%  of  the energy
> would be dissipated in the core.

I was not interested in examining the frequency response, saturation
effect or core losses. These are only important after the  core goes
into saturation.

I was  only interested in the result of switching at the peak  or at
the zero  crossing. This is clearly defined at the beginning  of the
document.

> The sharp  rise  in voltage and the  leading  inrush  current have
> frequency components that are way higher than mains frequency.

> Hence the  linear model you used will give inaccurate  results, to
> put it mildly.

> Unfortunately, building an accurate transformer model in  spice is
> not easy and depends on higher order functions that might or might
> not be  available in the flavour you use. Not to mention  that you
> will need  to  have  good   (measured)  numbers  on  the non-ideal
> behaviour of a transformer, which are also not easy to get by.

The saturation  and  core  losses   are  outside  the  scope  of the
investigation. The  investigation was only to examine the  effect of
switching at  the  peak or at the zero  crossing.  This  was clearly
stated at the beginning of the paper.

My analysis  correctly defined an unloaded transformer  as  the only
case where  switching  at  

Re: [time-nuts] One sure way to kill your FE-5680A or FE-5650A

[Bob Camp]

Hi

Thanks for the heads up !!

It almost sounds like they are doing some sort of “use flash as eeprom” trick 
and not 
quite getting it right. Maybe updating a “how many times turned on” counter in 
that 
memory space.

Bob


> On Jun 7, 2016, at 5:22 PM, Skip Withrow  wrote:
> 
> We recently had a customer that purchased an FEI FE-5650A (basically a
> repackage version of the FE-5680A) and reported that it worked for several
> hours, then died.  We promptly sent another unit, and he reported that it
> died as well.  He had nothing but power hooked to the unit.
> 
> On return of the first unit, it was examined and found to have corrupted
> code.  The corrupted code problem was thought to be associated with doing
> bad things to the serial port (like framing errors), and we still believe
> this to be the case.  However, the customer said only power was connected
> to the unit.
> 
> I was asking some questions about how he was powering the unit, when he
> said he turned on the power supply (a large HP variable supply) and turned
> the voltage up to +15V (our 5650's are single supply).  Ah hah, slowly
> ramping the voltage up on these oscillators appears to be a no no.
> 
> The second oscillator has now been examined and it too was confirmed to
> have corrupted code.  So, the word of warning is - DO NOT slowly ramp the
> supply voltage of FE-5680A and FE-5650A oscillators.  I can't say what
> slowly is, but this guy was good at killing them.  If I get some time I may
> try to repeat the results.
> 
> My advice was to set the supply at 15V and just turn it off and on.  I have
> not heard from him since.
> 
> If anyone out there has a 5680A or 5650A that does not lock, the code issue
> is very likely the problem.  I have seen several 5680 units as well as a
> few 5650 units with this problem.  The good news is that they can be
> fixed.  I would happily do this for any time-nut that has one if return
> postage is included with the unit.  The bad news is that we don't know the
> nature of the code problem that trashes the software (stack overflow, error
> handling routine, etc.) so units can only be restored to their original
> condition that still has the bug in the code.
> 
> Otherwise, the 5650 and 5680 are great values to get rubidium performance
> at very reasonable prices.  I have 1000's of hours on them and 100's of
> power cycles, with a lot of serial port use, so if treated correctly they
> are reliable units.
> 
> Regards,
> Skip Withrow
> RDR Electronics, Inc.
> 
> 
> Virus-free
> 
> <#DDB4FAA8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
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[time-nuts] One sure way to kill your FE-5680A or FE-5650A

[Skip Withrow]

We recently had a customer that purchased an FEI FE-5650A (basically a
repackage version of the FE-5680A) and reported that it worked for several
hours, then died.  We promptly sent another unit, and he reported that it
died as well.  He had nothing but power hooked to the unit.

On return of the first unit, it was examined and found to have corrupted
code.  The corrupted code problem was thought to be associated with doing
bad things to the serial port (like framing errors), and we still believe
this to be the case.  However, the customer said only power was connected
to the unit.

I was asking some questions about how he was powering the unit, when he
said he turned on the power supply (a large HP variable supply) and turned
the voltage up to +15V (our 5650's are single supply).  Ah hah, slowly
ramping the voltage up on these oscillators appears to be a no no.

The second oscillator has now been examined and it too was confirmed to
have corrupted code.  So, the word of warning is - DO NOT slowly ramp the
supply voltage of FE-5680A and FE-5650A oscillators.  I can't say what
slowly is, but this guy was good at killing them.  If I get some time I may
try to repeat the results.

My advice was to set the supply at 15V and just turn it off and on.  I have
not heard from him since.

If anyone out there has a 5680A or 5650A that does not lock, the code issue
is very likely the problem.  I have seen several 5680 units as well as a
few 5650 units with this problem.  The good news is that they can be
fixed.  I would happily do this for any time-nut that has one if return
postage is included with the unit.  The bad news is that we don't know the
nature of the code problem that trashes the software (stack overflow, error
handling routine, etc.) so units can only be restored to their original
condition that still has the bug in the code.

Otherwise, the 5650 and 5680 are great values to get rubidium performance
at very reasonable prices.  I have 1000's of hours on them and 100's of
power cycles, with a lot of serial port use, so if treated correctly they
are reliable units.

Regards,
Skip Withrow
RDR Electronics, Inc.


Virus-free

<#DDB4FAA8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
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Re: [time-nuts] THE Original Time Interval Counter

[Steve - Home]

I calibrated and repaired dozens of these beasts in the Air Force. A Fluke 
207-1 was our reference standard at the time. Still have a 207-1 on the shelf 
and the whip antenna in the attic!

Steve K. 



> On Jun 7, 2016, at 3:21 PM,   wrote:
> 
> Well, This is probably not the original but I remember using one "in the
> day"
> 
> Corby
> 
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[time-nuts] THE Original Time Interval Counter

[cdelect]

Well, This is probably not the original but I remember using one "in the
day"

Corby___
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Re: [time-nuts] Some FE405B data

[Attila Kinali]

On Tue, 7 Jun 2016 11:36:43 -0700
 wrote:

> Attached here is a long term AD plot of an FE405B.
> 
> Stays in the 10-13ths all the way up to 10,000 seconds!
> 
> This unit has only been operating for about 2 weeks.

This is interesting. Do you have an idea why your unit peforms so much
better than those that TvB measured[1]?


Attila Kinali


[1] http://www.leapsecond.com/pages/fe405/
-- 
Reading can seriously damage your ignorance.
-- unknown
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Re: [time-nuts] GPS NOTAMS issued for US west coast

[james machado]

Seems there are a bunch of NOTAMs on this subject though the US from
June 6 to June 11

https://pilotweb.nas.faa.gov/PilotWeb/noticesAction.do?queryType=ALLGPS=DOMESTIC#ZSE



On Tue, Jun 7, 2016 at 11:27 AM, Scott McGrath  wrote:
> All
>
> Check the GPS NOTAMs for the west coast apparently USG will be conducting GPS 
> interference testing at  NAS China Lake with a radius of 300NM
>
> Advisory states GPS unavailable for up to 6 hours at a time
>
> From 6 June to 9 June
>
> Sorry on a phone or would have copied NOTAM text
>
>
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Re: [time-nuts] Goodie for British Timenuts!!!

[Dan Rae]

On 6/7/2016 10:38 AM, cdel...@juno.com wrote:

RACAL MA259 FREQUENCY STANDARD FROM 1965

Looks neat


Corby,

Internally they're a rebadged Sulzer more or less.  There's been one for 
sale on eBay in the US for years, literally, at the somewhat ridiculous 
price of over $3,000.


item:
252399450511

only now slightly reduced!

One might wonder what state the 21 NiCads are in after all those years 
:^)  And I couldn't sell my Sulzer for $50 at the swap meet, and that 
had new NiCads.


They are remarkably stable if my Sulzer is anything to go by, and it has 
a lovely mechanical fine frequency adjustment behind that multi turn dial.


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Re: [time-nuts] Goodie for British Timenuts!!!

[John Ackermann N8UR]

Boy, that looks an awful lot like a re-branded Sulzer 5 with Sulzer power 
supply!

> On Jun 7, 2016, at 1:38 PM,   wrote:
> 
> Hi,
> 
> Saw this while trolling for goodies!
> 
> http://www.mullardmagic.co.uk/racal-ma259-frequency-standard-ra17-ra117-r
> af-navy-goldfinger-james-bond-ra1218-ra1772-ra1792-ma50-ra181
> 
> RACAL MA259 FREQUENCY STANDARD FROM 1965 
> 
> Looks neat
> 
> Cheers,
> 
> Corby
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Re: [time-nuts] Satellites in the Sky

[Gary E. Miller]

Yo Don!

On Tue, 7 Jun 2016 11:51:40 -0500
"Don Lewis"  wrote:

> While in U-Center, bring up the ‘World’ graphic and it will show you
> which satellites are visible to your location and which ones are
> being tracked.  

The gpsd client xgps also does this, just no 'world' backgrounnd.

> Put your GPS module in NMEA mode.

Not required for gpsd, it works in NMEA, u-blox binary mode, or mixed
mode.

RGDS
GARY
---
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
g...@rellim.com  Tel:+1 541 382 8588


pgp_2SlfDmIgI.pgp
Description: OpenPGP digital signature
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[time-nuts] Some FE405B data

[cdelect]

Attached here is a long term AD plot of an FE405B.

Stays in the 10-13ths all the way up to 10,000 seconds!

This unit has only been operating for about 2 weeks.

In a month I'll repeat this plot and also include the aging rate.

I have found that these oscillators exhibit less drift than most others I
have tested!

Cheers,

Corby Dawson___
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[time-nuts] GPS NOTAMS issued for US west coast

[Scott McGrath]

All

Check the GPS NOTAMs for the west coast apparently USG will be conducting GPS 
interference testing at  NAS China Lake with a radius of 300NM

Advisory states GPS unavailable for up to 6 hours at a time

>From 6 June to 9 June 

Sorry on a phone or would have copied NOTAM text


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[time-nuts] Goodie for British Timenuts!!!

[cdelect]

Hi,

Saw this while trolling for goodies!

http://www.mullardmagic.co.uk/racal-ma259-frequency-standard-ra17-ra117-r
af-navy-goldfinger-james-bond-ra1218-ra1772-ra1792-ma50-ra181

RACAL MA259 FREQUENCY STANDARD FROM 1965 

Looks neat

Cheers,

Corby
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[time-nuts] Satellites in the Sky

[Don Lewis]

I thought I would share a tip for those interested in ’visualizing’ the GPS 
constellation overhead – ‘seeing’ the satellites you are currently tracking.

While there are many GPS monitor apps available, ...some free - some not  
...each app will have various means to depict which satellites are overhead.  
Many have just tables of data.

I find the U-Blox, U-Center monitor app (free) most enlightening.

Besides being very well written and documented, it of course supports its’ 
proprietary U-Blox modules as well as many standard, NMEA-formatted ones.

Put your GPS module in NMEA mode.

While in U-Center, bring up the ‘World’ graphic and it will show you which 
satellites are visible to your location and which ones are being tracked.  Very 
educational to see them progress across the ‘earth’ .

Good use of colors for status.

You can get instant feedback from moving and relocating your antenna by 
watching which sats come and go and their color ‘status’.

All this makes the hobby more pleasurable, realistic and not so ethereal.

-Don
N5CID

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[time-nuts] THE Original Time Interval Counter

[Brooke Clarke]

Hi:

The stopwatch: 200 years old and still ticking
http://www.gizmag.com/birthday-200th-stopwatch/43431/?

--
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
The lesser of evils is still evil.

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[time-nuts] Jupiter-T timing receiver oddness

[Mark Sims]

I added support for the Jupiter-T receiver to Lady Heather and noticed 
something odd.  On the sat position/signal level map sat PRN 9 was always being 
drawn with a small black circle in the middle.  I could not figure out what was 
causing this... until I noticed that sat PRN 27 (which was visible, but 
untracked due to low signal level) was being reported as being at the same 
az/el as PRN 9.  The black dot was PRN 27's location/signal level being 
overlaid on PRN 9's
Analyzing some logged data, it looks like something about PRN27 confuses the 
Jupiter-T  Other receivers showed PRN27 in its proper position with a strong 
signal.  Doing a factory reset on the receiver (which flushes the almanac, 
ephemeris, etc) did not change anything.





  
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[time-nuts] Symmetricom TimeCreator 1000

[armstrong]

A Symmetricom TimeCreator 1000 has come into my possession.  It is a GPS
receiver with DOCSIS TIme interfaces, 10.24 MHz and 1 PPS outputs.  The
unit appears to function, however I have no manual.  I have stumbled
across a few commands that provide some information but if anyone has
more I would appreciate hearing from you!

Thanks in advance
Dave Armstrong

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