Re: [time-nuts] More ES100 WWVB Measurements

[Brooke Clarke]

Hi Wayne:

The problem is that when and how DST is implemented is a political decision at the state level.  When those rules that 
apply today are implemented in firmware (easy to do) the product tells the wrong time when those rules change.


In the case of the Heathkit GC-1000 the DST firmware changed the time when Colorado changed, but for me in California 
that clock was wrong twice a year for a couple of hours.

https://www.prc68.com/I/HeathkitGC1000.shtml

--
Have Fun,

Brooke Clarke
https://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
axioms:
1. The extent to which you can fix or improve something will be limited by how 
well you understand how it works.
2. Everybody, with no exceptions, holds false beliefs.

 Original Message 

> GPS has no bits for Daylight Savings

It isn't that hard to compute when DST changes and GPS has the advantage that, since it also knows position, a wall 
clock could also automatically set the timezone, much as our cellphones do.


> Has anybody looked into how much code it takes to implement DST?

In my WWVB generator for Arduino it took me about about 15 lines of C code and a small table (daysToMonth[]). The main 
function is getNthSundayOfMonth() which, in turn, use two other functions, getDayOfYear() and isLeapYear().  The 
daysToMonth[] table is used by getDayOfYear(). Then, the main code uses getNthSundayOfMonth() to get the 2nd Sundays 
of MARCH and NOVEMBER.


Wayne

On Tue, Jan 1, 2019 at 12:34 PM Brooke Clarke mailto:bro...@pacific.net>> wrote:

Hi Wayne:

DST.

GPS has no bits for Daylight Savings.  As far as I know only WWV and WWVB 
have those bits.
So for a clock displaying local time WWVB is the way to go.

-- 
Have Fun,


Brooke Clarke
https://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
axioms:
1. The extent to which you can fix or improve something will be limited by 
how well you understand how it works.
2. Everybody, with no exceptions, holds false beliefs.

 Original Message 
> While reading this thread and pondering whether to buy and fool around 
with
> an ES100-based module from Universal Solder, I suddenly found myself
> wondering if there was any advantage to using the time received from WWVB
> vs just using an inexpensive GPS receiver.  The ES100 module costs about
> $70, but I can get a GPS receiver, with antenna, for far less than that 
and
> I've had no trouble receiving GPS signals indoors with most modern 
receiver
> modules.
>
> I suppose the low power requirements of the ES100 might be an advantage
> when building battery powered clocks to mount on the wall, but it seems
> like some of the newer, ultra low power GPS modules intended for use in
> smart watches could also work in a battery-powered wall clock, especially
> if the receiver was only powered on a few times a day to update the time.
>
> And, finally, if GPS modules are (or will some become) a suitable
> replacement for WWVB receiver modules, do we really need WWVB in the 
modern
> age?  Perhaps there's some critical advantage to using WWVB to get the 
time
> but, offhand, I cannot think of it.  What am I missing?
>
> Wayne
>
> On Mon, Dec 31, 2018 at 4:30 PM Brooke Clarke mailto:bro...@pacific.net>> wrote:
>
>> Hi Joseph:
>>
>> Thanks for the patent link.  I've added it to my WWVB phase modulation
>> info at:
>> https://prc68.com/I/Loop.shtml#La_Crosse_UltrAtomic
>>
>> --
>> Have Fun,
>>
>> Brooke Clarke
>> https://www.PRC68.com
>> http://www.end2partygovernment.com/2012Issues.html
>> axioms:
>> 1. The extent to which you can fix or improve something will be limited 
by
>> how well you understand how it works.
>> 2. Everybody, with no exceptions, holds false beliefs.
>>
>>  Original Message 
>>> On Mon, 31 Dec 2018 12:00:02 -0500, time-nuts-requ...@lists.febo.com 

>>> wrote:
>>>
    time-nuts Digest, Vol 173, Issue 44
 Message: 7
 Date: Mon, 31 Dec 2018 04:04:22 -0800
 From: "Tom Van Baak" 
 To: "Discussion of precise time and frequency measurement"
       mailto:time-nuts@lists.febo.com>>
 Subject: Re: [time-nuts] More ES100 WWVB Measurements
 Message-ID: <96BB388753294278A9CDE96C1EA7D9AE@pc52>
 Content-Type: text/plain;    charset="UTF-8"

 Hi Graham,

 That's very nice work. And you have uncovered several unusual effects
 in the ES100. Bugs? Features? If we time nuts keep up the good work
 to evaluate this chip, we are likely at some point to get an
 informative response from the guys who designed it. They read
 time-nuts.
>>> I didn't see this mentioned, but I think I have found the 

Re: [time-nuts] question about multi-way measurement

[Hal Murray]

strom...@nexgo.de said:
> Over wired Ethernet you can expect to synchronize a bunch of systems to
> within a ~200µs envelope of absolute time and maybe a factor of 2x-3x  lower
> if you can control certain things more tightly than usual if you  run those
> system on a single hop switched LAN that have a GPS-based  stratum-1 NTP
> server.  For anything better than that you'd need PTP,  which unfortunately
> the rasPi is incapable of.  Or do you plan to use  the rasPi itself as the RX/
> TX?  The few  papers I've just looked up all  use Atheros 9k hardware. 

On the Raspberry Pi, the Ethernet is on USB so there is another source of 
timing error.  It's full speed USB rather than low speed USB so the timing 
noise isn't as bad as it could be - 1/8 ms vs 1 ms.  (I could be off on the 
numbers or names, but the general idea is correct.)

If you think you can avoid that by averaging, be sure you understand hanging 
bridges.

If you need good times on a Pi, consider a GPS hat.  The PPS goes in via a 
GPIO pin with an interrupt so the timing can be pretty good.



-- 
These are my opinions.  I hate spam.




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[time-nuts] FCC OTA pre-emption and restrictions on GPS antennas [was: Short term 10MHz source]

[Gregory Maxwell]

On Wed, Jan 2, 2019 at 4:03 AM Chris Burford  wrote:
> My current residence does not allow a permanent GPS antenna therefore I am 
> limited in its use.

[separate thread since I'm not answering the question that was actually asked.]

Perhaps not applicable to your situation, but in the US federal law
(47 C.F.R. Section 1.4000) substantially prohibits any restriction--
be it a local ordnance, zoning, deed covenant, private contract as
part of a lease, etc-- that prevents installing or using small (<1m)
antennas for data services in locations where you otherwise have
exclusive use. [AFAIK, it doesn't help if you're buried in a basement
and just don't have sky access at all]

My understanding is that originally the law went was created to
protect satellite TV services which were being impacted by cable
companies paying off developers to add deed restrictions that
prohibited any satellite TV dish, but over time it was amended to
cover more things including data services.

The FCC has a FAQ: https://www.fcc.gov/media/over-air-reception-devices-rule

I've never previously considered the application of this rule to GPS
antennas, since they're small and inconspicuous enough that I've never
run into much of a concern with them.

I am not a lawyer but it seems to me that the rule plausibly enough
covers a fixed GPS antenna. Someone having an issue getting approval
to install one could potentially make use of the rule in a couple
different ways:

* By arguing that the GPS timing receiver is covered by the current
rule and that federal law pre-empts any rule preventing the
installation, or
* Putting up an antenna under another service which is more obviously
covered (e.g. there are a number of L-band data services...) and
swapping out for the GPS after the fact, or
* By negotiating using the position that your alternative to running
the timing antenna would be installing a much more conspicuous 95cm
satellite TV dish ... "So, wouldn't everyone be happier if I could
just install the GPS antenna".

If a time-nut in the US has found themselves in the unfortunate
situation where a small-minded authority (such as a HOA) is
capriciously denying setting up a tastefully placed timing antenna one
of the above strategies might be useful.

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Re: [time-nuts] Short term 10MHz source

[Tom Van Baak]

> Use the Rb as your reference and log the time offset of its PPS.
> Manually steer vs a 10 hour GPS PPS data set once a week.
> You probably will stretch it out to a couple weeks after things settle in.

I'm with Bob here. Once a week, once a month, once a year, even once a 
lifetime: the choice depends on your accuracy requirements. For example, you 
can easily obtain ppb-levels (9 digits of accuracy) from an Rb with only once a 
year adjustment.

If you need to generate precise 10 MHz for some sort of transmitter or 
real-time customer then, yes, you should use a GPSDO -- a h/w solution to 
steering. But if all you are doing is making precise measurements and 
collecting data then a s/w solution is applicable. Consider it "data steering". 
You don't need EFC or Vref or DAC or other complexities of a GPSDO.

I do lots of multi-channel TAPR/TICC, TIC, picPET logging here. I rarely use an 
actual GPSDO. Instead I just log a GPS/1PPS as one of the counter(s) 
channel(s). That way you never have to calibrate your timebase, regardless if 
it's XO or OCXO or Rb. The timebase just free-runs. The calibration is done in 
s/w when you later process your counter readings. By recording a GPS tick along 
with all your DUT(s) you get tracking and calibration of your LO for free.

The TICC is designed to do this. It's not just a 2-input start/stop TIC, but a 
dual / independent timestamping counter.

This is similar to the trick people do with sound cards. Put a 1PPS into the 
R-channel and your signal into the L-channel. The inaccuracy and instability of 
the PC clock, or NTP, or RTC, or sound card xtal, or USB latency all drop out. 
It's a self-calibrating system.

/tvb


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Re: [time-nuts] HP3325B as LO for a transceiver or receiver? Phase noise?

[Chris Caudle]

On Wed, January 2, 2019 4:15 am, Leo Bodnar wrote:
> Here is the phase noise at 10MHz
> http://www.leobodnar.com/files/mini%20GPS%20clock%20-%20phase%20noise%2010MHz.png


Does that plot have enough resolution to show any narrow band spurs?  That
looks really clean for a programmable clock source.

-- 
Chris Caudle



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Re: [time-nuts] question about multi-way measurement

[Achim Gratz]

Charles Wyble wrote:

I built a dedicated server room in my house, with it's own air
conditioner. I've been working on overall instrumentation , especially
temperature.


If the rasPi is a dedicated system and does not serve extra tasks, just 
record its CPU temperature, no extra sensor needed.  The absolute 
temperature will be an almost constant offset from the ambient, so the 
changes are well preserved (except for short periods, e.g. when a cron 
job runs).


Any temperature transient will show up in the timing error, however 
small.  The FLL/PLL code in NTP will need to chase the changing crystal 
frequency and then eliminate the already accrued timing error.  The 
faster the transient, the larger the error.  So on-off aircon with 
forced convection is pretty close to worst case.



Could you share the snippets of the
PPS logging? I'm not 100% sure what you mean by the PPS timestamps.


Just reading from /dev/pps0 (system time and capture timestamp in my 
case), really; additionally system load and CPU temperature and logging 
the everything into a file.



Interesting. My ultimate application of this high precision timing is
driving TDMA wifi links as low cost as possible.
I'm not familiar with the requirements for that.  I suspect that the 
absolute timing between stations is actually pretty unimportant.  So the 
only thing that matters is that the relative timing error between 
beacons or syncs must keep below some threshold, which means the 
frequency offset of the system must be kept within (probably not too 
tight) bounds.  The latter is much easier to achieve and maintain.


Over wired Ethernet you can expect to synchronize a bunch of systems to 
within a ~200µs envelope of absolute time and maybe a factor of 2x-3x 
lower if you can control certain things more tightly than usual if you 
run those system on a single hop switched LAN that have a GPS-based 
stratum-1 NTP server.  For anything better than that you'd need PTP, 
which unfortunately the rasPi is incapable of.  Or do you plan to use 
the rasPi itself as the RX/TX?  The few  papers I've just looked up all 
use Atheros 9k hardware.



--
Achim.

(on the road :-)

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Re: [time-nuts] Short term 10MHz source

[Chris Burford]

I'll give the window placement a try and see if I can maintain a usable lock.

Thanks for the assistance.

Chris
 Hal Murray  wrote: 
> 
> > I do realise that the long term stability of the GPSDO is somewhat superior
> > to a Rubidium source. I'm planning on using my TICC to validate both my 
> > GPSDO
> > and RFS. I'm aware that such a short "power on" period is somewhat
> > counterproductive but I have no other options. I'd like to know if a 6-8 
> > hour
> > window for the GPSDO is sufficient for use as a 10MHz source for the TICC. 
> 
> Try using the Rubidium as the clock source for the TICC and watch the PPS 
> from 
> the GPSDO.
> 
> 
> > I have a situation in which I have access to a GPSDO 10MHz source but for
> > only about 10-12 hours at a time. My current residence does not allow a
> > permanent GPS antenna therefore I am limited in its use. 
> 
> Step two would be to see how well your GPSDO works with an internal antenna.  
> Sometimes it works with the antenna in a window.  ...
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
> 
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Re: [time-nuts] HP3325B as LO for a transceiver or receiver? Phase noise?

[Didier Juges]

Another option would be to phase lock the existing XO in the transceiver
instead of "replacing" it. With a very narrow PLL bandwidth, you should not
degrade the transceiver stock performance.

Didier KO4BB


On Wed, Jan 2, 2019, 4:17 AM Leo Bodnar  Here is the phase noise at 10MHz
> http://www.leobodnar.com/files/mini%20GPS%20clock%20-%20phase%20noise%2010MHz.png
> There will be overall noise increase of about 4dB at 15.6MHz
> Leo
>
> On 1 Jan 2019, at 17:00, time-nuts-requ...@lists.febo.com wrote:
> > From: Mark Goldberg 
> > Leo Bodnar's GPSDOs do provide good enough phase noise output.
> > I'l let him provide recent data if he wishes. You could feed it similarly
> > to how I feed an external frequency to my Perseus SDR, documented on my
> web pages.
>
> > On Tue, Jan 1, 2019 at 7:24 AM Chris Wilson 
> wrote:
> >> Could I use my HP3325B locked to a Trimble Thunderbolt GPS disciplined
> >> 10MHz oscillator as the master LO of my Kenwood TS-590S transceiver
> >> that has a LO at 15.6 MHz
>
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Re: [time-nuts] Short term 10MHz source

[Bob kb8tq]

Hi

Use the Rb as your reference and log the time offset of its PPS. Manually steer 
vs a 10 hour
GPS PPS data set once a week. You probably will stretch it out to a couple 
weeks after things
settle in.

More or less:

PPS starts at some offset. Call that zero. 

As the days go along: 

PPS goes positive = your frequency is high. 
PPS goes negative = your frequency is low.

A week later, look at the PPS relative to your zero. 
Do the math to work out the frequency offset. 
Measure frequency against the GPS with the TICC with maybe a 1,000 second gate 
time
Adjust the frequency by the required offset. 
Log the final PPS offset and use it as the new zero. 

There are a lot of other ways to do it, but the technique above does work. An 
alternative is
to monitor the EFC on the Rb and assume it has a constant slope. With a 
digitally tuned 
Rb, this all is “free”. 

Bob

> On Jan 1, 2019, at 10:56 PM, Chris Burford  wrote:
> 
> I have a situation in which I have access to a GPSDO 10MHz source but for 
> only about 10-12 hours at a time. My current residence does not allow a 
> permanent GPS antenna therefore I am limited in its use.
> 
> I do realise that the long term stability of the GPSDO is somewhat superior 
> to a Rubidium source. I'm planning on using my TICC to validate both my GPSDO 
> and RFS. I'm aware that such a short "power on" period is somewhat 
> counterproductive but I have no other options. I'd like to know if a 6-8 hour 
> window for the GPSDO is sufficient for use as a 10MHz source for the TICC.
> 
> I appreciate any and all comments.
> 
> Regards,
> 
> Chris
> 
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Re: [time-nuts] HP3325B as LO for a transceiver or receiver? Phase noise?

[Leo Bodnar]

Here is the phase noise at 10MHz 
http://www.leobodnar.com/files/mini%20GPS%20clock%20-%20phase%20noise%2010MHz.png
There will be overall noise increase of about 4dB at 15.6MHz
Leo

On 1 Jan 2019, at 17:00, time-nuts-requ...@lists.febo.com wrote:
> From: Mark Goldberg 
> Leo Bodnar's GPSDOs do provide good enough phase noise output.
> I'l let him provide recent data if he wishes. You could feed it similarly
> to how I feed an external frequency to my Perseus SDR, documented on my web 
> pages.

> On Tue, Jan 1, 2019 at 7:24 AM Chris Wilson  wrote:
>> Could I use my HP3325B locked to a Trimble Thunderbolt GPS disciplined
>> 10MHz oscillator as the master LO of my Kenwood TS-590S transceiver
>> that has a LO at 15.6 MHz

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Re: [time-nuts] HP3325B as LO for a transceiver or receiver?

[Dave B via time-nuts]

Hi.

Usually on a crowded band, to be nice to the RF neighbours (often
ourselves!)  Irrespective of the "mode" used, and/or getting the "best"
performance (small signal sensitivity) from a receiver.

Also, when multiplying/mixing up to microwave frequencies, again for a
clean signal.

The OP wanted to use it as an external reference signal for a Kenwood
radio (from memory.)  But how much of it's existing phase noise
signature is from the "reference", and how much from the other PLL's and
synthesizers it has internally may make what a Time Nut might regard as
a noisy external reference perfectly OK to use.

It's something that does interest a lot of people (especially VHF and up
DX'ers) where some popular makes of rig are very much worse than others!

However, few have the kit needed to make definitive "measurements", or
the ability to understand them "in the real world".  (Me included!)

73 & HNY

Dave B (G0WBX)

On 02/01/2019 04:03, time-nuts-requ...@lists.febo.com wrote:
> I wonder if some of the amateur modes also have 
> that need?

-- 
Created on and sent from a Unix like PC running and using free and open source 
software.
::


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Re: [time-nuts] Short term 10MHz source

[David G. McGaw]

Just inside a window can work for a GPSDO.  One of our labs at Dartmouth 
has metallic-tinted windows, so for that we hang a little puck antenna 
just outside.  Not ideal, but it gets signal.

David


On 1/1/19 11:53 PM, Hal Murray wrote:
>> I do realise that the long term stability of the GPSDO is somewhat superior
>> to a Rubidium source. I'm planning on using my TICC to validate both my GPSDO
>> and RFS. I'm aware that such a short "power on" period is somewhat
>> counterproductive but I have no other options. I'd like to know if a 6-8 hour
>> window for the GPSDO is sufficient for use as a 10MHz source for the TICC.
> Try using the Rubidium as the clock source for the TICC and watch the PPS from
> the GPSDO.
>
>
>> I have a situation in which I have access to a GPSDO 10MHz source but for
>> only about 10-12 hours at a time. My current residence does not allow a
>> permanent GPS antenna therefore I am limited in its use.
> Step two would be to see how well your GPSDO works with an internal antenna.
> Sometimes it works with the antenna in a window.  ...
>
>

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