Re: [time-nuts] How good is the left end of your ADEV curve?

[Henry Hallam]

On Wed, Jan 25, 2017 at 1:35 AM, Volker Esper  wrote:
> What can I do at home, to observe such processes? Or is it way beyond any
> imagination to participate in any such experiments?

It's not exactly direct observation, but you can participate by
joining the Einstein@Home project to use your computer's spare CPU
cycles to search for events in LIGO data (as well as radio and gamma
ray telescopes):

https://einsteinathome.org/

Henry
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Re: [time-nuts] New PPB rated TCXO

[Henry Hallam]

On Mon, Oct 10, 2016 at 11:53 PM, Poul-Henning Kamp  wrote:
> I take it they know how to price a gem like that ?
>
> Any ball-park numbers for us ?

I don't have any price info for the "Super-TCXO" but I'd be surprised
if it were crazy, SiTime's other products are all pretty reasonably
priced.

On Mon, Oct 10, 2016 at 11:27 PM, djl  wrote:
> But how the heck did they get some? According to the website, even data
> sheets are not available.

I imagine they got in touch with the manufacturer via the
prominently-displayed email address on the webpage :)  Having the
prospect of buying at least a few reels' worth probably helped too.

Henry
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Re: [time-nuts] New PPB rated TCXO

[Henry Hallam]

I can attest that that oscillator was a lifesaver recently in a
project I was tangentially involved with.  They had tried several
TCXOs and were plagued with thermal and vibration sensitivity.  They
dropped in the SiTime and it worked like a charm.

Henry

On Mon, Oct 10, 2016 at 7:02 PM, Nick Sayer via time-nuts
 wrote:
> The video linked on that page is particularly interesting (if you take it on 
> face value that they're not faking it. ;) ).
>
> Sent from my iPhone
>
>> On Oct 10, 2016, at 8:03 AM, Robert LaJeunesse  wrote:
>>
>> For general group information, as SiTime datasheet is not open to the public 
>> (yet?).
>>
>> https://www.sitime.com/products/precision-super-tcxo
>>
>> Actually a MEMS oscillator, comparison video against quartz TCXO is 
>> interesting.
>>
>> Claimed Key Features:
>> - 30x better dynamic performance for macro cells, small cells, syncE and 
>> optical networks
>> - 3e-11 Allan Deviation (ADEV)
>> - 0.2 ps/mv PSNR, eliminating dedicated LDO
>> - No activity dips or microjumps
>> - 10x better dynamic stability, replacing OCXOs in IEEE 1588 applications
>> - 1 to 5 ppb/°C frequency over temperature slope
>> - -40°C to +105°C operation uniquely enables fan-less outdoor equipment
>> - 20x greater vibration resistance ensures continuous system operation
>>
>> Frequency range 1MHz to 220MHz (via 2 product types) so some form of 
>> synthesizer/divider is inherent.
>>
>> Bob L.
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Re: [time-nuts] OT stuffing boards: was GPS interface/prototyping board

[Henry Hallam]

On Thu, Jun 23, 2016 at 1:09 PM, Nick Sayer via time-nuts
 wrote:
> It all sort of depends on what you call “reasonable.” PNP assembly is a bit 
> like PCB fab in that there are rather large set-up costs and the per-unit 
> cost after that is quite low, which favors volume.
>
> Any way you slice it, I’d expect that 10 boards is too small a number for it 
> to be economical. I’ve done 10-20 *panels* of boards at a time with SBA, and 
> that’s worked out ok, but that’s amortizing the cost over a couple hundred 
> units at a time.

Tempo Automation in San Francisco is trying to fill this gap in the
market for prototype quantities of boards.  I used them a couple of
years ago and they did a good job for a good price.  Looking at their
website now (http://www.tempoautomation.com/) it appears they've
expanded into fabbing the board for you as well as assembling it.

Henry
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Re: [time-nuts] GPS altitude somewhat wrong?

[Henry Hallam]

Per 
https://www.topoquest.com/map.php?lat=40.02486=-105.24468=nad27=2=auto=d=zoomin=m
the address in your signature is close to the 5250 ft (geoidal)
contour.

Henry

On Wed, Jun 8, 2016 at 3:18 PM, Henry Hallam <he...@pericynthion.org> wrote:
> Some of that is probably the difference between the geoid (what your
> surveyed maps report height relative to) and the WGS84 ellipsoid (what
> your GPS reports heights relative to).  At Boulder that difference is
> only about 15 meters, though.
>
> Generally with VDOP < 2 and a reasonably modern receiver the accuracy
> of a GPS altitude measurement should be better than about 20 meters.
> I'm not sure if the Thunderbolt counts as such.
>
> How flat is Boulder?  Do you have a proper surveyed elevation of your 
> location?
>
> Henry
>
> On Wed, Jun 8, 2016 at 1:33 PM, Van Horn, David
> <david.vanh...@backcountryaccess.com> wrote:
>>
>> I have just installed a Thunderbolt here to get our time and frequency 
>> equipment all on the same page.
>> As I was looking at the display on Lady Heather, I was noticing that the GPS 
>> altitude seems rather wrong.
>> We are in Boulder CO, which is nominally 5430' and the antenna is about 20' 
>> off the ground.
>> The display (near overdetermined position) reads 1589.72991 meters or 5216 
>> and change in feet.
>> Altitude is a big deal around here. :)
>>
>> I suppose 214' isn't that outrageous, but it does bring me to a question:
>>
>> How accurate is the altitude number really?
>>
>> Thanks.
>>
>>
>> --
>> David VanHorn
>> Lead Hardware Engineer
>>
>> Backcountry Access, Inc.
>> 2820 Wilderness Pl, Unit H
>> Boulder, CO  80301 USA
>> phone: 303-417-1345 x110
>> email: 
>> david.vanh...@backcountryaccess.com<mailto:david.vanh...@backcountryaccess.com>
>>
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Re: [time-nuts] GPS altitude somewhat wrong?

[Henry Hallam]

Some of that is probably the difference between the geoid (what your
surveyed maps report height relative to) and the WGS84 ellipsoid (what
your GPS reports heights relative to).  At Boulder that difference is
only about 15 meters, though.

Generally with VDOP < 2 and a reasonably modern receiver the accuracy
of a GPS altitude measurement should be better than about 20 meters.
I'm not sure if the Thunderbolt counts as such.

How flat is Boulder?  Do you have a proper surveyed elevation of your location?

Henry

On Wed, Jun 8, 2016 at 1:33 PM, Van Horn, David
 wrote:
>
> I have just installed a Thunderbolt here to get our time and frequency 
> equipment all on the same page.
> As I was looking at the display on Lady Heather, I was noticing that the GPS 
> altitude seems rather wrong.
> We are in Boulder CO, which is nominally 5430' and the antenna is about 20' 
> off the ground.
> The display (near overdetermined position) reads 1589.72991 meters or 5216 
> and change in feet.
> Altitude is a big deal around here. :)
>
> I suppose 214' isn't that outrageous, but it does bring me to a question:
>
> How accurate is the altitude number really?
>
> Thanks.
>
>
> --
> David VanHorn
> Lead Hardware Engineer
>
> Backcountry Access, Inc.
> 2820 Wilderness Pl, Unit H
> Boulder, CO  80301 USA
> phone: 303-417-1345 x110
> email: 
> david.vanh...@backcountryaccess.com
>
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Re: [time-nuts] Segal law: freq difference for GPSDO

[Henry Hallam]

On Tue, Mar 29, 2016 at 5:48 PM, Vlad  wrote:
>
> I tried to see the 1PPS on my oscilloscope. Here is the series of
> screenshots from that experiment:
>
> https://www.patoka.ca/OCXO/TBvsSL/

>From those scope shots it looks like one or both of the GPSDOs does
not have any kind of lock to GPS time.  The PPS leading edges from the
two receivers should be aligned to within a few tens to hundreds of
nanoseconds, but yours are hundreds of milliseconds apart.

The screenshot you have at
https://www.patoka.ca/OCXO/TBvsSL/StarLocIImonitor.png shows a
receiver only tracking one satellite, which is not sufficient.  Maybe
the antenna signal connection to that unit is poor or maybe it's
defective. The filename says StarLoc but the window title says
Thunderbolt, which is it?

Good luck,
Henry
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Re: [time-nuts] Segal law: freq difference for GPSDO

[Henry Hallam]

If you put the PPS outputs of the two GPSDOs into an oscilloscope and
trigger on the leading edge of one of them, what does the other look
like?

Henry

On Tue, Mar 29, 2016 at 12:56 PM, Vlad  wrote:
>
>
> Hello,
>
> I am looking for for the advise regarding some strange difference in
> frequency between of two GPSDO: Trimble Thunderbolt and Datum Starloc II
>
> Measuring by HP 5386A counter it shows something around 0.014 delta.
> If I connect TB as REF source then I am getting numbers like this:
> 10.01396 Mhz
> If I connect StarLoc II as REF source then I am getting following:
> 9.98612 Mhz
>
> May be somebody could recognize, what 10.014 Mhz could be used for ?
>
> TB Lady Heather screenshot
> http://www.patoka.org/OCXO/TB-LH-Mar.png
>
> Allan Deviation for several hours looks like this:
> http://www.patoka.org/OCXO/TB-SL.png
>
>
> I connected both GPSDO to Rigol DS1102E Oscilloscope to see the phase
> difference. And its shows me the ellipse which change its orientation left
> to right and vice versa.
>
> Its classical case of Segal's law: "A man with a watch knows what time it
> is. A man with two watches is never sure". This is exact situation. Now I am
> not sure which GPSDO (if any) is more accurate.
>
> I have no third GPSDO (or equivalent) to compare. TB and Starloc connected
> to the same GPS Antenna distribution amplifier. So basically both using the
> same antenna. Both of them was turned on at relatively the same time and
> both was warmed up for few days.
>
> I have a theory, that may be StarLoc II was customized somehow to produce
> the freq. slightly different from 10Mhz. But its just a theory.
> Is it worth to compare 1PPS outputs using something like AD8302 + DAC + MCU
> ?
>
> --
> WBW,
>
> V.P.
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Re: [time-nuts] GPS Signal Simulator for GnuRadio

[Henry Hallam]

Nice.  I threw one together too a few weeks ago:
https://github.com/henryhallam/peregrine/commits/sig_gen

Henry

On Sun, Jun 21, 2015 at 11:33 PM, Attila Kinali att...@kinali.ch wrote:
 Moin,

 This just came in trough my feeds. Maybe someone finds it interesting:
 https://github.com/osqzss/gps-sdr-sim

 Attila Kinali

 --
 I must not become metastable.
 Metastability is the mind-killer.
 Metastability is the little-death that brings total obliteration.
 I will face my metastability.
 I will permit it to pass over me and through me.
 And when it has gone past I will turn the inner eye to see its path.
 Where the metastability has gone there will be nothing. Only I will remain.

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Re: [time-nuts] I wish to shorten GPS antenna cable - should I let receiver find the position again?

[Henry Hallam]

On Thu, Apr 23, 2015 at 5:03 AM, Dr. David Kirkby (Kirkby Microwave
Ltd) drkir...@kirkbymicrowave.co.uk wrote:
 I have an HP 58503A which I am using as a frequency source only - not
 to tell the time. I want to shorted the antenna cable a bit, but are
 wondering if I should let the GPS receiver finds it position again. Or
 either of the following better

 * Remove antenna cable, put a new N plug on, and screw it back in with
 the receiver kept powered up all the time.
 * Power off GPS receiver and power it back on with the cable connected.

 I'm not moving the antenna, so the actual position will not change,
 but of course the signals will get to the receiver a bit sooner.

If the goal is minimizing downtime and duration of degraded quality
output, I would go with the former.  The 58503A will enter holdover
mode.  It will keep its oven warm and retain its learned oscillator
model parameters.  When you reconnect the antenna it will pick right
back up where it left off, with minimal settling time.

Henry
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Re: [time-nuts] serial parsing program

[Henry Hallam]

RealTerm is my go-to for this sort of thing on Windows, though it
might not be quite as flexible as you'd like.
Linux: just mung together a pipeline involving things like xxd, awk, grep..

Henry

On Tue, Mar 24, 2015 at 3:22 PM, Cash Olsen radio.kd5...@gmail.com wrote:
 I'd like to find a program that has a very flexible serial input and can be
 easily setup to parse a binary sentence. Specifically, U-Blox timing but
 more general purpose would be nice for future projects. Has to be able to
 handle 1, 2, and 4 byte fields, and checksums would be nice also. Should
 run on Windows for the immediate project but Linux for next projects.

 --
 S. Cash Olsen KD5SSJ
 ARRL Technical Specialist
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Re: [time-nuts] June 30 2015 leap second

[Henry Hallam]

Such slewing solutions are OK for Google.  They wouldn't work well for
one of the systems I work with, which uses system time to calculate
the position of a LEO satellite for purpose of pointing a 7.6 meter
X-band dish.  Half a second of error corresponds to a pointing error
of 0.5 degrees, well outside the main lobe of the antenna beam.

Anecdotally yours,
Henry

On Fri, Jan 9, 2015 at 2:30 PM, Hal Murray hmur...@megapathdsl.net wrote:

 t...@patoka.org said:
 1s/24h = 1/86400 which is approximately 12ppm. That means that Aging  Offset
 could slow down my clock for 1 second if I'll apply the maximum  value one
 day ahead (roughly). I need to do some experiments first. ;-)  Its looks too
 unreliable for me.

 If you do it that way, your clock will be off by a whole second just before
 midnight when the leap-second brings it back into sync.  If you tweak your
 clock from noon-noon, it will only be off by 1/2 second at midnight when the
 sign-bit of the error flips.

 --
 These are my opinions.  I hate spam.



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Re: [time-nuts] June 30 2015 leap second

[Henry Hallam]

Correct me if I'm wrong, but as I understand it the tzfile in the
tzone package is not used to update the system time - that relies on
NTP or similar.  Rather, the leap second info in the tzone files is
made available for applications to use, primarily for calculating time
differences in the past.

Henry

On Fri, Jan 9, 2015 at 6:17 AM, Tom Van Baak t...@leapsecond.com wrote:
 I couldn't help noticing that Debian just issued an update
 to tzone, so that means Linux systems now know about the
 leap second.

 -Chuck Harris


 Hi Chuck,

 Linux systems now know about the leap second -- this is a very dangerous 
 assumption. And one reason why leap seconds have gotten out of hand the past 
 decade.

 Just because you observe one tz update from Debian does not imply that all 
 Linux systems on planet earth (or in space) magically know about leap 
 seconds. There must be millions (billions?) of embedded or isolated systems 
 -- from web servers to desktops to military systems to gadgets to Raspberry 
 Pi's to mobile phones, that have not, and will not ever receive this update.

 /tvb
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Re: [time-nuts] June 30 2015 leap second

[Henry Hallam]

The difference between GPS time and UTC (due to leap seconds) is
broadcast in the GPS navigation message[1] so all but the most poorly
designed GPS modules should take care of it and output the correct UTC
time.

I'm not going to get into the mess of unix epoch time.  Basically,
it's not a continuous time scale.  There is some information on the
wikipedia page[2], and plenty of discussion on various mailing lists
such as LEAPSECS.

Henry

[1] Specifically, page 18 of subframe 4 - see IS-GPS-200G page 112,
114 and 119-121.
[2] https://en.wikipedia.org/wiki/Unix_time#Leap_seconds

On Tue, Jan 6, 2015 at 1:01 PM, d0ct0r t...@patoka.org wrote:

 Hello,

 As I am in the process of creation of my own Nixie clocks. And it probably
 good time frame to clarify one thing about leap seconds. In my project I am
 using GPS module as an option to have current UTC time and also to have 1PPS
 signal to do auto-adjustment for external RTC module. The question is how
 usually GPS modules handle leap seconds ? Is it satelates who send UTC time
 to GPS module or GPS module has firmware with leap second information
 hard-coded ?
 The same question is for UNIX epoch time. How computers knows if it is
 necessary to add leap seconds ? Lets say I am using very simple script to
 calculate UNIX time for specified date:


 
 #!/usr/bin/perl

 use Time::Local;
 my ($d, $m, $y);
 my $time;


 @myYears = ('01/06/2000', '01/06/2015', '01/06/2038', '01/06/3000');

 foreach (@myYears) {
 ($d, $m, $y) = split '/', $_;
 $time = timelocal(0,0,0,$d,$m-1,$y);
 printf %ld\n\r, $time;
 }

 ==

 It will produce the following output:

 959832000
 1433131200
 2158977600
 32516740800


 I am not sure if its take leap second consideration. Most likely not. And
 that means its only accurate for the present and pas time. Right ? For my
 clock I already implement the function for the leap second and I am able to
 add/remove number of seconds from the time I receiving from GPS or any other
 source. But it will be more inetersting if clock could do it automagically
 and shows me that famous 60 number without human interaction. Any advise
 for this ? Thanks !

 Regards,

 V.P.


 On , Tom Van Baak wrote:

 Just announced: there will be a positive leap second at the end of
 June 30 2015 UTC (that's Wednesday July 1st for most of the world).

 As usual we time nuts will have a leap second party -- where we
 capture and share the magic hh:59:60 display on as many different
 clocks and instruments as possible.

 /tvb

 More info:
 ftp://hpiers.obspm.fr/iers/bul/bulc/bulletinc.dat
 http://hpiers.obspm.fr/eop-pc/

 And for those of you who want to know how long each day really is:
 ftp://hpiers.obspm.fr/iers/bul/bulb_new/bulletinb.dat
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 --
 WBW,

 V.P.

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Re: [time-nuts] CGSIC: FW: New NANU 2014090

[Henry Hallam]

The Swift Navigation Piksi project may be of interest:

http://swiftnav.com/piksi.html

It has an FPGA for correlation with an ARM Cortex-M3 for tracking
loops and navigation.  The hardware and ARM firmware is open source,
but the FPGA design is closed-source at the moment.  However, I don't
see why the FPGA would need adapting for use with L2C  L5.

I know the Swift Nav folks are looking into a multi-frequency product.
One of the main obstacles is a commodity front-end solution, and
antennas at reasonable prices.

Henry

On Tue, Dec 16, 2014 at 5:01 PM, Magnus Danielson
mag...@rubidium.dyndns.org wrote:
 Jim,

 On 12/17/2014 01:46 AM, Jim Lux wrote:

 On 12/16/14, 4:29 PM, Magnus Danielson wrote:

 Jim, Bob,


 There is a fair amount of work along the full path.

 LNA with some L2 and L5 filters is pretty easy.

 I think you still want to have a correlator baseband processing in say
 an FPGA.


 well, yes.. but I don't know if there's any handy open source free cores
 out there for that.

   I do know grin of an implementation that does the acq and track in a
 pair of Xilinx 2-3000 parts and does the nav solution in a SPARC V8, but
 it's not open source and it's definitely export controlled.


 For that application it needs to break both the limits at the same time, for
 sure.

 Seems that what's out there is mostly record bits and postprocess in
 C++ or Matlab Several textbooks even include it.


 It's good for many purposes as you get yourself up to speed.

 There is naturally stuff to be done on the L2C and L5 modulated signals,
 but it goes in a relatively slow paze so that even modest processors can
 keep up with it.


 Indeed.. we do 24 channels (where channel is one PRN at one frequency)
 with a 3 frequency solution without making a 66 MHz LEON2 based SPARC
 sweat too much.


 That's why it would be intriguing if someone had the FPGA stuff out there.


 Indeed. I did a GPS correlator core once, but it had issues to fit the FPGA
 I had at hand at the time. The software receiver I did was not at all doing
 real-time, but it did do many of the crucial points and was a nice exercise.

 It would still be an expensive project, I suspect.  Either you'd have a
 few $50-100 boards that would need interfacing and a lot of time, or a
 $1000 board with less time.


 One hopes that in a few years, multifrequency stuff will become available.


 Indeed. Maybe a complete implementation just needs to hit the web..

 Cheers,
 Magnus

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Re: [time-nuts] FYI: Galileo satellite recovered and transmitting navigation signals

[Henry Hallam]

It's a global system and modern receivers are already capable of
augmenting GPS solutions with measurements from Galileo satellites.

Henry

On Fri, Dec 5, 2014 at 1:08 PM, Richard Solomon w1...@earthlink.net wrote:
 Dumb Question Time ...

 Is the Galileo available in North America or only for our overseas brethren
 ?

 Tnx, Dick, W1KSZ



 On 12/5/2014 8:16 AM, Edesio Costa e Silva wrote:

 Partial recovery of Galileo constellation:

 http://www.southgatearc.org/news/2014/december/galileo_satellite_recovered_and_transmitting_navigation_signals.htm

 Edésio
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Re: [time-nuts] NPR Story I heard this morning

[Henry Hallam]

On Mon, Nov 3, 2014 at 1:18 PM, Mike Feher mfe...@eozinc.com wrote:
 Anyway, regarding time and gravity, I certainly believe the mathematics of 
 Einstein and others, however, I have a hard time believing that man-made 
 instruments to measure the effects of gravity on time is valid. For example 
 in a Cesium clock, time is a function of the transition time between two 
 hyperfine lines of Cesium atoms. So, does gravity affect this transition time 
 within the Cesium atoms? It may very well, but, I am not smart enough to know 
 that. Maybe someone can help.

This may not be a very satisfactory explanation, but in a nutshell
it's not the atomic transition time that changes with gravitational
potential, but *time itself*.  And remember, it's a *relative* effect
- you can only measure it when you compare two clocks at different
heights, never just by looking at one by itself, no matter how good it
is.

 Also, when someone mentioned moving a very sensitive scale up in elevation 
 and noting the difference due to gravitational effects, also seems odd to me. 
 Seems like even in the most sensitive scales, weight is measured as the 
 difference between the weighing platform and the body of the instrument. Here 
 again, moving the whole assembly up in elevation it would seem to me that 
 gravity would affect both the platform and the body, and the relative weight 
 indicated should remain the same. What am I missing besides gray matter? 
 Thanks - Mike

Weighing scales do not work by measuring the gravitational attraction
between the scale and the object to be measured.  They measure the
attraction between the earth and the object to be measured. When you
go up a hill, you move the apparatus and the object, but not the
earth.

Henry
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Re: [time-nuts] Sun Outage

[Henry Hallam]

On Thu, Oct 9, 2014 at 11:18 AM, Hal Murray hmur...@megapathdsl.net wrote:
 What's the beam width of the DirectTV antennas?  Does it agree with the 3 or
 4 minutes at the back-of-envelope level?

DirecTV is a Ku/Ka-band system operating with a 460mm dish antenna.
At Ka-band, the 3dB full-width of the beam is 2.4 degrees.  The earth
rotates at 0.25 degrees per minute, giving approx 10 minutes for the
sun to cross the beam assuming it crosses directly through the center
of the beam.

However, a little googling[1] suggests that in fact the DirecTV
satellite signal usually has enough margin to overcome the sun noise,
but that the C-band feed[2] that DirecTV uses at their uplink station
to receive programs from their providers may itself suffer from solar
conjunctions.

Henry

[1] http://www.dbstalk.com/topic/202779-sun-interference-message/
[2] http://www.prss.org/solar-outage-rules
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Re: [time-nuts] Homemade GPS Receiver

[Henry Hallam]

On Fri, Sep 26, 2014 at 8:25 AM, Dr. David Kirkby (Kirkby Microwave
Ltd) drkir...@kirkbymicrowave.co.uk wrote:
 As I say, without stating the properties of the receiving antenna,
 absolute power levels are not a sensible unit.

Indeed, there is an implicit assumption of a ~omnidirectional
(hemisphere-pattern) antenna, with a typical effective gain around 1
dBi.

Since the GPS signals come from all parts of the sky this is pretty
much required, unless you're using fancy beam steering techniques.

Perhaps slightly sloppy terminology but the meaning is clear, to me anyway :)

Henry
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Re: [time-nuts] Practical Survey-In Accuracy?

[Henry Hallam]

I would call that done.

Henry

On Sat, Aug 23, 2014 at 4:38 PM, Bob Stewart b...@evoria.net wrote:
 I've had the LEA-6T sitting in survey-in mode for about 17 hours, and at this 
 point, the u-center software says that the Mean 3D Std Dev is 0.109 meters.  
 Given that my antenna is just a puck at the peak of the attic (never got 
 around to adding the DIY choke-ring), has this reached the silly number 
 phase, or should I let is simmer overnight before calling it done?

 Bob - AE6RV
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Re: [time-nuts] Caveats on Allan Deviation with ultra stable oscillators

[Henry Hallam]

On Fri, May 30, 2014 at 3:24 PM, Poul-Henning Kamp p...@phk.freebsd.dk wrote:
 Always locate your DUTs physically orthogonal to each other.

Good point.  Of course, if you have more than three in an ensemble
then the ensuing hyperdimensional vortex may also cause unexpected
cross-coupling.

Henry
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Re: [time-nuts] HP Z3805A GPSDO Oven Heater Voltages

[Henry Hallam]

John,

I have a similar unit (probably from the same seller), advertised as
an Z3805A upgraded to the features of 58503A, whatever that is
supposed to mean.

Mine also does not get warm on top, though it appears to be providing
a decent 10 MHz output and indicates GPS lock.  This is the best
reference in the lab at the moment so I can't truly speak to the
stability of the output.

Thanks for the heads-up that the outer oven is not being turned on by
the CPU.  I haven't opened up the case yet but will do so as soon as
my order of round tuits arrives :)

Henry

On Thu, Apr 24, 2014 at 10:15 AM, John Stuart j.w.stu...@comcast.net wrote:
 Jarl,
 Thank you for your help on this.  It appears that either; the CPU has a bad
 output pin, some unknown command has turned the heater off, or the firmware
 is programmed that way.  The 10 MHz frequency had always been very 'stable',
 and I didn't know there was a problem until I bought a 2nd HP Z3805A and
 felt how warm the (50C) insulated double oven should feel.

 I am trying to communicate with the seller in Hong Kong.  So far he hasn't
 acknowledged that the CPU output pin can turn-off the heater.

 By the way, your projects onhttp://risums.net/hjem/oz9mo/index.html
 http://risums.net/hjem/oz9mo/index.html  are very interesting and described
 very clearly.  Nice work!

 John, KM6QX


   _

 From: Jarl Risum [mailto:jarl.ri...@gmail.com]
 Sent: Thursday, April 24, 2014 5:23 AM
 To: John Stuart
 Subject: Re: HP Z3805A GPSDO Oven Heater Voltages


 John,


 Thanks for the feedback and congratulations with your result so far.

 Unfortunately I have no further information regarding the function of the
 outer oven control signal from the processor board. You are probably right
 in assuming that the signal might be used to prevent the outer oven from
 overheating in case the thermistor went open, since the processor on the
 main board do monitor the outer oven heater voltage through P2/9.
 Speculating further: It might also be used by manufacturers to switch off
 the outer oven heater circuit permanently in HP Z3805's using the 5 MHz MTI
 OCXO if a suitable RS-232 command exist for this purpose.


 Cheers from OZ9MO / Jarl

 in Denmark

 Some of my Time-Nuttery:  http://risums.net/hjem/oz9mo/index.html





 2014-04-24 3:13 GMT+02:00 John Stuart j.w.stu...@comcast.net:



 Jarl, OZ9MO
 Thank you for those two links!  They have the information I needed, and are
 very well 'hidden' on the internet.

 I have had partial success.  Per the work-around on www.realhamradio.com, I
 pulled P2-8 on the power board up to +5V, and the outer heater came on and
 is now being controlled by temperature controller on the power board; TP104
 is modulating around 15.75 V.

 However the heater on/off control signal from the main circuit board
 (normally connected to P2-8) is still OFF at 0.0 V.  For some reason (maybe
 firmware) the units CPU is not turning on this signal.  I am thinking about
 permanently wiring +5V to P2-8 to keep the heater enabled.

 Why would the outer oven ever be turned OFF ??  Maybe to prevent
 over-temperature damage if the NTC sensor fails?

 When I bought this HP Z3805A from the Hong Kong seller a couple of years
 ago, it was advertised as having been upgraded to the features (firmware?)
 of the HP(Symmetricam) 58503A.  Does anyone else have this 'model' and does
 the Double Oven XO keep the unit's top very warm, like it should?

 John Stuart, KM6QX
 Lafayette, CA



   _

 From: Jarl Risum [mailto:jarl.ri...@gmail.com]
 Sent: Wednesday, April 23, 2014 2:22 AM
 To: j.w.stu...@comcast.net
 Subject: HP Z3805A GPSDO Oven Heater Voltages


 Hi John


 You will find a comprehensive description of the outer oven heater circuit
 here:

 http://www.ko4bb.com/Manuals/05%29_GPS_Timing/Z3801/Z3801A_Outer_Oven/Web_Pa
 ge/Z3801A%20Outer%20Oven%20Controller.htm


 In my HP Z3805A the outer oven circuit is identical to the circuit in HP
 Z3801.


 A description of a Z3801A outer oven fault similar to the one you have can
 be found here:

 http://www.realhamradio.com/oven-confusion.htm


 You will also find a suggestion for a simple remedy.


 Good luck.


 Cheers from OZ9MO / Jarl

 in Denmark



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Re: [time-nuts] Beaglebone NTP server

[Henry Hallam]

Thanks for all the hints everyone.  Lots to try!

Henry

On Thu, Mar 27, 2014 at 2:41 AM, Iain Young i...@g7iii.net wrote:
 On 26/03/14 23:18, Brian Lloyd wrote:

 Well, yeah. I figured that I would run the 1pps from my T-bolt to a GPIO
 line with appropriate clamping to 3.3V.

 But if anyone has done this before and run into anything of note, that
 would be nice to know ahead of time.


 Can I suggest you consider FreeBSD ? You can use the TIMER4-7 input pins
 as PPS input for a better PPS. See the following URL for details:

 http://lists.freebsd.org/pipermail/freebsd-arm/2013-February/004769.html

 If I recall correctly, the patch is in the FreeBSD 10 snapshots for the
 Beaglebone, so you don't need to apply it, but you will need to enable
 PPS and ensure one of the four TIMER pins is set to input in the DTS
 and recompile.


 Iain

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Re: [time-nuts] Beaglebone NTP server

[Henry Hallam]

Hi Gabs,

I have a Z3805A and a Beaglebone, and would like to set up an NTP
server for the lab.  Any kernel drivers and/or setup hints would be
appreciated :)

Cheers,
Henry

On Thu, Jun 20, 2013 at 7:37 PM, Gabs Ricalde gsrica...@gmail.com wrote:
 On Thu, Jun 20, 2013 at 3:39 AM, Chris Howard ch...@elfpen.com wrote:

 Are you using the original BeagleBone or the new BeagleBone Black?

 I'm using the original BeagleBone. it should work on the BeagleBone Black.

 Will you have any details available about what parts are needed to set it up?

 If your GPS receiver is using 3.3V logic, wiring it up is
 straightforward, similar to the Raspberry Pi NTP server. I will probably
 setup a page describing this.
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Re: [time-nuts] high (spacial) precision GPS in Kickstarter

[Henry Hallam]

I know the Swift Nav guys and they are working on adding various forms
of customizable timing inputs and outputs to the Piksi.  It's also an
open-source project, so it's pretty flexible in that regard.

Henry

On Sat, Jan 25, 2014 at 4:56 AM, Magnus Danielson
mag...@rubidium.dyndns.org wrote:
 On 25/01/14 11:42, Anders Wallin wrote:

 AFAIK 'normal' RTK does not provide a clock solution. There's something
 called 4D RTK which does:
 http://saegnss1.curtin.edu.au/Publications/2010/Feng2010Four.pdf
 apparently the results can be very good - but I think the errors quoted
 are
 for time-transfer between two RTK receivers (?).

 If there are papers comparing time-transfer with dual-frequency PPP to
 this
 4D RTK I'd be interested..


 I think you need to differentiate between common-view time-transfer and the
 precision you get from the system itself.

 RTK uses the carrier phase corrections achieved from known position to kind
 of high-speed delta signals as received in it's neighbourhood. This affects
 both the position and time shifts of the receiver. If the RTK base also has
 a good timebase and is maintained in a good way time-wise, then both
 position and time gets good corrections.

 It's about the same type of errors as you get in the difference between
 common-view time-transfer comparisons.

 If you only do L1 C/A RTK, then naturally you will benefit from the RTK as
 you have no double frequency observations of your own. If you have
 double-frequency receiver, RTK assist to work on the tropospheric
 corrections and sat orbit and time errors for which a pure double frequency
 receiver isn't able to crack on it's own.

 Cheers,
 Magnus

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Re: [time-nuts] OT : different Rx and Tx baud rate on same port

[Henry Hallam]

You could also consider making a simple gadget with your
microcontroller of choice, that presents an interface to the PC of a
fixed baud rate (perhaps 115200) and handles the weirdo split rates
for the GPS gadget on one or two of its other ports.

Henry

On Sat, Dec 7, 2013 at 12:18 PM, Hal Murray hmur...@megapathdsl.net wrote:

 b...@lysator.liu.se said:
 Looking at the stty unix command. It seems clear that split baud rates has
 been supported at one time.

 On Linux, man termios gives lots of API details.

 On NetBSD and FreeBSD, that gets an overview.  man tcsetattr gets the API
 details.

 If you use stty to change things, the new info is sticky.  So if you have a
 program that is all set to go except that the baud rates aren't right and
 that program doesn't smash the baud rates, you can set them with stty and
 your program should work.  I haven't tried it with split baud rates, but the
 normal (non-split) case works.

 If your gizmo uses simple ASCII, you can test things with cat /dev/wherever
 and things like this on another terminal
   echo blah blah...  /dev/wherever


 --
 These are my opinions.  I hate spam.



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Re: [time-nuts] GPSDO for my rubber duckie

[Henry Hallam]

The parameters you'll want for conversion between MCAT and mean solar
time are given daily in the IERS bulletins:
http://hpiers.obspm.fr/eop-pc/products/bulletins/bulletins.html

By making use of these you should be able to do much better than the
slightly inelegant leap second rubberization-over-10-seconds method
you had proposed.  Your rubber seconds should be smooth and
continuous, to the limit of the IERS measurement accuracy.

Good luck,
Henry

On Mon, Aug 1, 2011 at 12:23 PM, Michael Sokolov
msoko...@ivan.harhan.org wrote:
 Hello time-nuts,

 I've been on this list for several years now and I've made a few little
 comments on occasion, but this will be my first real technical post.

 I desire to build a timekeeping apparatus which I have nicknamed the
 rubber duckie, or a Rubber Time Generator.  As I've voiced very
 vigorously on the leapsecs list, I wish to live my personal life on a
 timescale that is anchored to Earth rotation via elastic (rubber) seconds
 rather than leap seconds or PHK/ITU-style total decoupling.  I do not
 wish to go into the reasons for that in this thread - the leapsecs list
 would be better for that - but here I am soliciting technical advice
 with the actual implementation.

 In technical terms I envision a device (a physical piece of hardware)
 that takes MCAT (Muggle Consensus Atomic Time) as input and produces
 UTR (UT Rubber) as output.  MCAT is my term that encompasses all of UTC,
 TAI, GPS time, other GNSS time etc, basically all the various timescales
 which produce their 1 PPS at exactly the same time but label their
 seconds differently.  As a matter of practical implementation my choice
 of specific MCAT realization for Version 1 of my rubber duckie will
 probably be GPS.

 Thus what I am soliciting on this list is advice with choosing a good
 GPS receiver / GPSDO for my application, which is feeding MCAT input to
 my rubber duckie.  My requirements are:

 * I want to be able to disable the leap second correction in the GPS
  receiver, i.e., have it output time such that I can add a constant 19
  to it and get TAI.  (Or TAPF = Temps Atomique Pedant-Free, which is
  defined to be identical with TAI in every respect except that it is
  free from the edict of though shalt not use TAI.)

 * I'm striving to move away from the Gregorian calendar wherever I can.
  Therefore, if the GPS receiver is trying to be user-friendly and
  convert the date part of GPS time into Gregorian format, I want to be
  able to disable that function.  I want MJD numbers instead of Gregorian
  dates, or GPS week numbers / day-of-week / time-of-day.

 * I think I need a GPSDO rather than just a GPS receiver.  The hardware
  design I have in mind for my rubber duckie is a custom PowerPC board
  on which I will run a specially modified and heavily stripped-down
  version of 4.3BSD-Quasijarus, an embedded PowerPC port thereof.

 In order to run a version of 4.3BSD-Quasijarus on my custom PowerPC
 board and make it do what I want (generate UTR from MCAT), I would like
 to implement a circuit on my board that generates an interrupt per
 millisecond.  These millisecond interrupts need to be aligned with 1 PPS
 such that every 1000th millisecond interrupt also serves as an on-time
 mark for MCAT (TAI/UTC/GPS/etc) seconds.

 Someone please correct me if I'm missing some other simpler way, but it
 seems to me that in order to generate these 1 ms interrupts with the
 properties I require, I will need a 10 MHz input in addition to 1 PPS,
 hence the need for a GPSDO rather than just a GPS receiver.  I envision
 my clock interrupt generation logic working as follows:

 * Starting at power-up boot, divide 10 MHz input by 1 and produce an
  interrupt every 1 ms.  At this point these interrupts aren't aligned
  with anything, but they are good enough for the OS to boot.

 * The FPGA in which this circuit resides gets an acquire lock command
  from the software.  It hunts for an external 1 PPS pulse, generates
  its own 1 ms interrupt at the same time (modulo a few cycles of 10 MHz
  for logic and synchronizer delays), and resets its divide-by-1
  logic from there, such that all subsequent 1 ms interrupts will follow
  in proper sequence.

 * In the preceding description the external 1 PPS pulse is acted upon
  only once, and all subsequent 1 ms and 1 s timing is derived from
  10 MHz.  However, there will also be a sanity check circuit that will
  look for the external 1 PPS in the vicinity (+/- 1 ms maybe?) of the
  internally-derived 1000th 1 ms interrupt.  If the internal and
  external 1 PPS signals disagree, signal an error indication to the
  software.  The software will then declare the UTR output as possibly
  invalid and resync itself; the resync sequence will include telling
  the FPGA to resync itself to the external 1 PPS.

 In order for my clock interrupt generation circuit to work as I envision,
 the 10 MHz and 1 PPS signals going from the GPSDO to my rubber duckie
 will need to meet 

Re: [time-nuts] GPS interference and history...

[Henry Hallam]

On Thu, Jun 9, 2011 at 2:42 PM, Jim Lux jim...@earthlink.net wrote:

 GPS orbits are tough from a radiation standpoint too.


In particular, the orbits are considerably worse for radiation than
GEO, and photovoltaic panels are quite susceptible to radiation.  Of
course you could put a GNSS in GSO but I think it's not as favorable
from a constellation design point of view, and the launches are more
expensive.

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Re: [time-nuts] light squared test

[Henry Hallam]

https://pilotweb.nas.faa.gov/PilotWeb/noticesAction.do?queryType=ALLGPSformatType=DOMESTIC

05/013 (A1221/11) - AIRSPACE GPS IS UNRELIABLE AND MAY BE UNAVAILABLE
WITHIN A RADIUS OF 175NM AND CENTERED AT 360709N/1151140W OR
THE LOCATION ALSO KNOWN AS THE LAS VOR 324.8 RADIAL AT 2.9 NM
FROM THE SURFACE TO FL400 AND ABOVE. PILOTS WITHIN A 175 MILE
RADIUS OF THE LAS VEGAS AREA ARE HIGHLY ENCOURAGED TO REPORT
ANOMALIES TO THE GPS SIGNAL DURING THIS TEST. 0700-1300 DLY. 16 MAY 07:00 2011
UNTIL 27 MAY 13:00 2011. CREATED: 12 MAY 18:40 2011


On Wed, May 18, 2011 at 7:50 PM, tom jones epoch_t...@yahoo.com wrote:

 The local NBC news in las vegas reported tonight (5-18-11) that next week, 
 piolets flying at night may find gps unreliable or unuseable do to 
 lightsquared testing broadband internet equipment in a frequency band 
 adjacent to gps frequency.  And that las vegas falls within a 350 mile radius 
 of this testing..

 Anybody have anymore info on this test. I've been reading posts here on 
 timenuts about likely interference to gps receivers . And  the fcc rushing 
 license's for lightsquared. But I wasn't aware of any tests.  Does anyone 
 know where lightsquared is testing its transmitters that las vegas would fall 
 within lightsquared's 350 mile radius.

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Re: [time-nuts] Isolated input oscilloscopes

[Henry Hallam]

On Sat, Dec 11, 2010 at 3:25 PM, Mark Sims hol...@hotmail.com wrote:

 A little off topic,  but needed for a time-nutty application:  4 channel 
 scope with isolated inputs that is affordable.  I have a 2 channel Tek 
 THS730A.  The Tek TPS2014 is rather pricey.  Does anybody know of something 
 affordable?

The TPS2014 is pricey but it is a real pleasure to use.  I haven't run
across anything as capable and convenient with isolated inputs and
four channels.  Running on batteries is also much more useful than I
expected it to be,

-- 
Henry Hallam

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Re: [time-nuts] GPS antenna info needed

[Henry Hallam]

On Wed, Dec 8, 2010 at 6:16 PM, Perry Sandeen sandee...@yahoo.com wrote:
 My magnetic base hockey puck amplified GPS antenna for my Lucent receiver 
 died.  I had purchased it at the Dayton Hamvention so I don’t remember the 
 dealer.

 I’ve found quite a few sellers on Amazon that are in the USA and their prices 
 are all about the same.

 Does anyone have a recommendation?

 I’d rather spend a few dollars more for a quality unit but I don’t know if 
 they are all from the same supplier in china and they only difference is the 
 dealers price.


I really like the Antenna Factor GPS-SH: http://tinyurl.com/2fxm6n7

I've bought them from Mouser but it looks like you might be able to
order direct from the manufacturer.

They seem to outperform the China clones by several dB, and have a
relatively narrow (~60MHz) bandpass filter at the antenna that reduces
out-of-band noise.

Don't forget to use a ground plane.

Henry

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Re: [time-nuts] Alternative to GPS?

[Henry Hallam]

On Tue, Oct 5, 2010 at 9:04 PM, Neville Michie namic...@gmail.com wrote:
 Hi,
 How far could you get passing time around from amateur station to station
 with a two way handshake system that establishes the instantaneous delay
 on the two way path and assumes a delay of half that value? A time relay.
 The stations would need their own short term clocks so they could keep
 their own time between contacts, and somewhere you would need heros
 with primary standards to synch the whole system.
 You would not be able to find a good position, because you would not know
 the
 propagation mode.

A lot of work has been put into NTP which does a fine job of this and
considers a lot of subtleties.  In practice it has precision limits.

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Re: [time-nuts] Symmetricom 58535A GPS antenna splitters FS

[Henry Hallam]

Hi Mike,
Do you still have any of these splitters available by any chance?

Thanks!
Henry

On Fri, Mar 26, 2010 at 4:29 PM, Mike Feher mfe...@eozinc.com wrote:
 I have the same items available in original sealed bags, for $35 each for
 one, $65 for two, and $120 for 4, plus actual priority shipping. So for one
 that is about $6, and for 2 or 4 it is about $11. Sorry to advertise on
 here, but, I know I am not setting a precedent. PayPal or checks welcome. I
 am now in Atlanta, but will be home tomorrow. Regards - Mike


 Mike B. Feher, N4FS
 89 Arnold Blvd.
 Howell, NJ, 07731
 732-886-5960



 -Original Message-
 From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
 Behalf Of J. L. Trantham, M. D.
 Sent: Friday, March 26, 2010 6:55 PM
 To: Discussion of precise time and frequency measurement
 Subject: Re: [time-nuts] GPS antenna splitters

 I have used one of these (ePay item 370265750113) and it works well.

 Joe



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-- 
Henry Hallam

Sent from my Laptop

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Re: [time-nuts] GPS SVN26 / PRN26

[Henry Hallam]

Right, but that was over days ago. I think my problem was just some
unusually strong multipath.

Thanks
H

On Aug 13, 2010 2:46 PM, Magnus Danielson mag...@rubidium.dyndns.org
wrote:
 On 08/13/2010 09:41 PM, Henry Hallam wrote:
 Is anyone else having issues with satellite 26 at the moment?

 There is scheduled activity for it:

 GPS OPERATIONAL ADVISORY 225
 SUBJ: GPS STATUS 13 AUG 2010

 1. SATELLITES, PLANES, AND CLOCKS (CS=CESIUM RB=RUBIDIUM):
 A. BLOCK I : NONE
 B. BLOCK II: PRNS 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14
 PLANE : SLOT B11, D1, C2, D4, E3, C5, A4, A3, A1, E6, D2, B4, F3,
 F1
 CLOCK : RB, RB, CS, RB, RB, RB, RB, CS, CS, CS, RB, RB, RB, RB
 BLOCK II: PRNS 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28
 PLANE : SLOT F2, B1, C4, E4, C3, E1, D3, E2, F4, D21, B2, F21, A6,
 B3
 CLOCK : RB, RB, RB, RB, RB, RB, RB, RB, RB, CS, RB, RB, CS, RB
 BLOCK II: PRNS 29, 30, 31, 32
 PLANE : SLOT C1, B21, A2, E5
 CLOCK : RB, CS, RB, RB
 2. CURRENT ADVISORIES AND FORECASTS :
 A. FORECASTS: FOR SEVEN DAYS AFTER EVENT CONCLUDES.
 NANU MSG DATE/TIME PRN TYPE SUMMARY (JDAY/ZULU
 TIME START - STOP)

 2010102 222106Z JUL 2010 16 FCSTDV 210/1345-211/0145
 2010103 292144Z JUL 2010 16 FCSTSUMM 210/1411-210/2126
 2010104 292146Z JUL 2010 26 FCSTDV 215/1715-216/1715
 2010105 03Z AUG 2010 26 FCSTSUMM 215/1726-215/
 B. ADVISORIES:
 NANU MSG DATE/TIME PRN TYPE SUMMARY (JDAY/ZULU
 TIME START - STOP)

 C. GENERAL:
 NANU MSG DATE/TIME PRN TYPE SUMMARY (JDAY/ZULU
 TIME START - STOP)

 2009025 061455Z APR 2009 GENERAL /-/
 2010068 111551Z APR 2010 GENERAL /-/

 Cheers,
 Magnus

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[time-nuts] GPS SVN26 / PRN26

[Henry Hallam]

Is anyone else having issues with satellite 26 at the moment?

Thanks
Henry

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Re: [time-nuts] one-off PC board

[Henry Hallam]

On Wed, Aug 11, 2010 at 11:11 PM, Dick Moore rich...@hughes.net wrote:
 I have a board layout that I need made, simple single-side, 2.3 x 6.5 inches. 
 Any suggestions on where I can get this made at a reasonable price? The mask 
 layout I have is a printout from a pdf document that has black where the 
 traces are and is full-size.


www.barebonespcb.com is high quality, fast and cheap.  Many board
houses offer a similar service.  The caveat is that they all expect
Gerber files rather than PDF.  You might be able to call and see if
they can take PDF as a special case.  Otherwise try to dig up the CAD
files that were used to create the PDF, or recreate the layout in
Eagle, gEDA, PCB Artist etc and export as Gerber.
Or skip the professional board houses and find someone with an etch
tank who can help.

Henry Hallam

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[time-nuts] Buffer / distribution amplifier for TCXO

[Henry Hallam]

Dear time nuts,

Background:
I have built a GPS receiver based around the SE4120L front end IC [1].
 I used a KT3225 TCXO [2] at 16.3676MHz driving the front end through
a 10nF series capacitor as in the example circuit in [1].  Inside the
front end, this oscillator is multiplied up to form a local oscillator
at 1571.2896 MHz.  The 16.3676MHz signal is also divided to form a
4.0919MHz sampling clock.  Digital I and Q samples then go to a DSP
where the GPS signal processing is done in software.  My receiver
works nicely, getting it online was a boatload of fun and I'm hoping
to make it available soon along with open-source software as a GPS
experimenter's kit.

Problem:
I'd like to clock multiple receivers from a single 16.3676MHz
oscillator, in order to combine measurements from multiple antennas.
The clocks must be at the same frequency, i.e. from the same source,
but it is not necessary that they have any particular phase
relationship as phase offsets are removed in the navigation
processing.

What sort of distribution amplifier should I use to split the output
of one TCXO into four front ends?  Do I need some kind of impedance
matching network?  How would I go about designing that?  This sort of
analog/RF design is unfamiliar territory for me, though I'd like to
learn.

The TCXO advertises a minimum output level of 0.8Vpp into (10kohm in
parallel with 10pF).  The front end requires a minimum oscillator
drive level of 0.2Vpp.  The front end datasheet lists recommended
crystal parameters including a load capacitance of 10pF (typ),
although I don't know whether or not that refers to the front end
input capacitance.

My guess is that phase noise performance is not particularly crucial,
at least by time-nuts standards.  I guess it would be nice if the
amplifier didn't make the phase noise significantly worse than it
already is from the cheap TCXO.

Many thanks,
Henry Hallam

[1] 
http://www.sige.com/support/download-form.html?dl=DST-00059_SE4120L_Datasheet_Rev_3p5_CYW_May-26-2009.pdf
[2] http://global.kyocera.com/prdct/electro/pdf/tcxo/172_e.pdf

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Re: [time-nuts] Buffer / distribution amplifier for TCXO

[Henry Hallam]

On Wed, Aug 4, 2010 at 1:50 PM, Bruce Griffiths
bruce.griffi...@xtra.co.nz wrote:

 The TCXO output waveform is presumably a clipped sinewave as required by the
 SE4120L?

I posted the waveform at
http://www.pericynthion.org/stuff/KT3225_500mV_per_div.jpg
Does that count as clipped sine?  If not, it seems to work anyway.


 In which case a linear distribution amplifier is probably required.

 With only a ~3V supply available, options for the distribution amplifier
 topology are somewhat limited.

I'm making a custom board that will include the TCXO and distribution
amplifier (as well as some digital stuff to allow the 4 receivers to
communicate), so it can have whatever power supplies it needs.

 In principle you could use an emitter follower driving 4 other emitter
 followers with a resistor in series with the emitters of the output devices
 and the AC coupled loads to match the source to the interconnecting cable
 impedance to minimise reflections without requiring excessive dissipation in
 the emitter followers.
 With the low voltage supply available, using an RF choke is series with the
 emitter follower's emitter to ground resistor will also be useful in
 achieving the required dynamic range.

Thanks.


Henry

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Re: [time-nuts] buffer amp transformers...

[Henry Hallam]

The spec sheet lists them as being good to 10MHz; would they be ok at
16MHz with a little more loss, or should I worry about resonances with
parasitic capacitance?

73 de Henry M0HMH in Santa Cruz

On Wed, Aug 4, 2010 at 9:14 PM,  k6...@comcast.net wrote:
 I think I'm a time-nut; as symptoms I include (1) a lot of Mini-Circuits 
 parts on my bench, (2) searches on eBay for Mini-Circuits goodies, and (3) 
 the desire to know how my LPRO, 10811, and Thunderbolt are different, and how 
 much better a Thunderbolt would be with a 10811 double-oven in it...

 Anyway, here's an eBay auction for 25 T-626 1:1:1 transformers -- item 
 number: 220544907085
 http://cgi.ebay.com/25-Mini-Circuits-T-626-RF-Transformers-0-01-10-MHz-/220544907085?cmd=ViewItempt=LH_DefaultDomain_0hash=item335980374d

 which look like just the thing for this amp...

 73 de bob k6rtm in silicon valley


 -
 Message: 4
 Date: Thu, 05 Aug 2010 10:05:39 +1200
 From: Bruce Griffiths bruce.griffi...@xtra.co.nz
 Subject: Re: [time-nuts] Buffer / distribution amplifier for TCXO
 To: Discussion of precise time and frequency measurement
 time-nuts@febo.com
 Message-ID: 4c59e433.6000...@xtra.co.nz
 Content-Type: text/plain; charset=iso-8859-1; Format=flowed

 Bruce Griffiths wrote:

 In which case a linear distribution amplifier is probably required.

 With only a ~3V supply available, options for the distribution
 amplifier topology are somewhat limited.
 In principle you could use an emitter follower driving 4 other emitter
 followers with a resistor in series with the emitters of the output
 devices and the AC coupled loads to match the source to the
 interconnecting cable impedance to minimise reflections without
 requiring excessive dissipation in the emitter followers.
 With the low voltage supply available, using an RF choke is series
 with the emitter follower's emitter to ground resistor will also be
 useful in achieving the required dynamic range.

 Bruce

 A more efficient buffer amplifier circuit schematic is attached.

 The series transformer feedback stage has high input impedance and an
 output impedance matched to the transmission line (yes it works well
 with long transmission lines as well).
 However a trifilar wound RF transformer is required.

 In principle the various GPS receivers could be connected to taps along
 an end terminated transmission line using feedthrough connections with
 compensation for the tap shunt capacitance if necessary.

 A lower impedance line (eg 50 ohms) could also be driven at the expense
 of a higher collector current.
 In this case the value of R3 would need to be reduced to around 100 ohms
 or so.

 Bruce
 -- next part --
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 --

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 End of time-nuts Digest, Vol 73, Issue 12
 *
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-- 
Henry Hallam

Sent from my Laptop

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Re: [time-nuts] Faulty GPS SAT # 16 on Lady Heather

[Henry Hallam]

Yes, forecast downtime due to delta V maneuvering.  I believe it's
related to the reorganisation of the constellation from 21+3 to 24+3:
http://blogs.agi.com/navigationAccuracy/?p=315

Henry


On Thu, Jul 29, 2010 at 2:41 PM,  b...@lysator.liu.se wrote:
 It seems it is beeing moved.

 56   16  Launched 29 JAN 2003; usable 18 FEB 2003; operating on Rb std
           Scheduled unusable 29 Jul 1345 UT to 30 Jul 0145 UT for
             repositioning maintenance (NANU 2010102)

 from   ftp://tycho.usno.navy.mil/pub/gps/gpstd.txt

 btw the Elmer Perkins Rb's beats most/all space CS out to a few days.
 Since the ground crew updates clock preditions every day, there is not
 that much need for the Cs _long_ term stability.

 --

   Björn

 Once again, one of the 8 received satellites (#16) delivers no
 contribution to the time ensmble, although it got is over 40dbc
 strength. Lady Heather (beta 3.00) shows a hollow circle in the diagram,
 marked yellow in the list, and it has zero CLOCK BIAS and ACCU=0.

 Does anybody know, if that satellite is defect (e.g. Cs down), or if it
 has a special task, i.e. military purposes only?

 Frank

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-- 
Henry Hallam

Sent from my Laptop

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Re: [time-nuts] Naval Jelly at home depot 25-35% Phosphoric acid

[Henry Hallam]

On Sat, Apr 10, 2010 at 3:44 PM, Bill pha...@wcc.net wrote:
 I keep at least a couple of gallons of phosphoric acid on hands at all
 time

That can't be good for your skin.  Can I suggest some moisturizer instead?

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Re: [time-nuts] Chilean quake shifted Earth's axis. The length of the day shorter by 1.26 microseconds ?

[Henry Hallam]

How would one go about verifying this? The angular difference after 1
year is about 3E-8 radians, which is probably well beyond the absolute
pointing accuracy of any telescope, and swamped by lunar tidal
deceleration anyway.

Henry

On Mon, Mar 1, 2010 at 7:36 PM, mc0fred mc0f...@gmail.com wrote:
 Interesting that the effect could be this large.

 http://www.smh.com.au/technology/sci-tech/chilean-quake-shifted-earths-axis-nasa-scientist-20100302-peqe.html?autostart=1



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-- 
Henry Hallam

Sent from my Laptop

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Re: [time-nuts] Chilean quake shifted Earth's axis. The length of the day shorter by 1.26 microseconds ?

[Henry Hallam]

Of course... I am designing a GPS receiver as my day job and didn't
think of that ;)

Henry

On Mon, Mar 1, 2010 at 8:36 PM, Mark Sims hol...@hotmail.com wrote:

 Pretty trivial to do with GPS where a 1 ns error is under 1 foot of position 
 error (and a geodetic grade GPS can give sub-millimeter accuracy)...  even a 
 cheap consumer grade unit is under 10 feet of error.   1.26 us of orbital 
 change is over 1100 feet of error.

 One trick is to compare the pre-earthquake GPS almanac/ephemeris data with 
 the post earthquake data.  I suspect that a lot of geodetic monitoring 
 stations are scrambling to keep up with what the earth is currently doing.


 ---
 How would one go about verifying this? The angular difference after 1
 year is about 3E-8 radians, which is probably well beyond the absolute
 pointing accuracy of any telescope, and swamped by lunar tidal
 deceleration anyway.


 _
 Hotmail: Free, trusted and rich email service.
 http://clk.atdmt.com/GBL/go/201469228/direct/01/
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Henry Hallam

Sent from my Laptop

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Re: [time-nuts] Are the days of buying a crystal numbered?

[Henry Hallam]

Anybody know what its performance is like under vibration?

Henry

On Mon, Feb 22, 2010 at 5:32 AM, Marco IK1ODO -2 ik1...@spin-it.com wrote:
 There are several kits around using the Si570 serires of oscillators. I
 built the FA-SY and it's very nice:

 http://www.funkamateur.de/download-files/dl1fac_FA-SY-Umbau.pdf

 FA-SY includes a program to trum the frequency, and a simple oven to heat
 the oscillator. It stays in some parts in 10^9, and is spectrally very
 clean. I expected it to be much worse :-) - I may post some plots, if anyone
 is interested.

 Then see http://www.mydarc.de/dg8saq/SI570/index.shtml and
 http://www.sdr-kits.net/USB/USB_Description.html

 73 - Marco IK1ODO


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Henry Hallam

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Re: [time-nuts] TBolt OCXO replacement

[Henry Hallam]

Timing newbie here, so please educate me - why does aging matter?
Isn't the whole purpose of a GPSDO to completely eliminate long-term
drift?

Thanks
Henry

On Tue, Feb 16, 2010 at 2:36 PM, Bob Camp li...@cq.nu wrote:
 Hi

 A similar question though would be - once you have done all the
 corrections to the setup of the TBolt (damping, time constant,
 sensitivity) what's left to fix?

 I would *guess*:

 Lower aging
 Better TC
 Better short term

 Aging will likely get better the longer you leave the existing oscillator on
 power. You also may be able to pick between units to find the best of 4 or
 something like that.

 TC can be improved a number of ways simply by helping the existing part. I
 think we have gone over that in about 300,000 messages so far.

 Short term stability is about the only thing I can see that's still on the
 list.

 That gets you to the question - just how good do you think the 1 second AVAR
 is on the existing oscillator, independent of the TBolt environment?

 If for instance you have a 2.5x10^-12 OCXO in yours, you would only see a
 significant improvement with a sub 1.0x10^-12 OCXO. That sort of bounds your
 OCXO shopping list right there.

 Bob

 -Original Message-
 From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
 Behalf Of Scott Newell
 Sent: Tuesday, February 16, 2010 1:06 PM
 To: time-nuts@febo.com
 Subject: Re: [time-nuts] TBolt OCXO replacement

 At 11:37 AM 2/16/2010 , WarrenS wrote:

In the ever ending battle to improve my TBolt's performance, I am in the
 process of upgrading a OCXO replacement I did to it a while back.
It would be Interesting to hear suggestions from others that have done
 similar sort of things and the results they have achieved.

 Did you check out John Miles's writeup?

 http://www.thegleam.com/ke5fx/tbolt.htm



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Re: [time-nuts] No 1 PPS output on a Tbolt

[Henry Hallam]

I use both a DS1052E and a couple of Tek scopes.  I do like the
DS1052E and think it offers great value at 25% the price of a
comparable Tek.  I love the long memory.
The Teks still feel more solid (in an accuracy/reliability/usability
sense).  I noticed some trigger jitter on the DS1052E.

Henry

On Fri, Feb 12, 2010 at 9:14 AM, Scott Burris slbur...@gmail.com wrote:
 I got a DS1052E a few months ago and I'm quite happy with it.  It's great
 for looking at events
 like this thread has been discussing (although am I the only person who
 still owns a Radio Shack
 logic probe from the 70's which would work just fine for detecting 1PPS??).

 I won't be giving up my three analog Tek scopes anytime soon though.  The
 DS1052E
 tends to be a bit noisy looking at low level signals, and anything over
 50Mhzish pushes
 me back to the analogs.  The user interface isn't always obvious, as it
 seems most buttons
 have multiple function and menus abound on this thing.  But user interface
 problems seem to
 be common on lots of test equipment these days -- I wonder what kind of
 scope Steve Jobs
 would design :-)

 I find myself using it mostly as a kind of 2 channel analog logic analyzer,
 setting up a single
 capture from the trigger and studying what happened before and after the
 trigger.  First use
 was looking at an I2C bus, not only to look at the data, but also the rise
 time of the signals.

 For the price it can't be beat, and it fills a diagnostic hole for me that I
 can't easily fill with
 the other equipment at my (hobbyist) disposal.

 Scott

 Brooke Clarke wrote:

 Hi Bob:

 I have been studying digital scopes for some time and have the Rigol
 DS1052E on the way.
 http://www.prc68.com/I/RigolDS1052E.shtml
 Rigol may make the low end scopes that are sold by Agilent.  This model
 goes for a little over $400 and gets excellent reviews (links on the above
 web page).

 Have Fun,

 Brooke Clarke
 http://www.PRC68.com



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