[time-nuts] Frequency Mixers

[John Moran, Scawby Design]

The latest Technical Article from Analog Devices may be of interest to some of 
you -

https://www.analog.com/en/technical-articles/the-changing-landscape-frequency-mixing-components.html?ADICID=EMAL_WW_P354759_MIX-NL-PN_1077=DM23404


John

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[time-nuts] Re: GPSDO - GPS1300-10-1000 by RFX Ltd. UK

[John Moran, Scawby Design]

Thank you all for your comments both here and direct, greatly appreciated. I 
think I now have a more sensible plan.

Running LH on a PI as a stand-alone device sounds interesting. If there are 
project details around, I would be interested in a copy, thanks.

John

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[time-nuts] Re: GPSDO - GPS1300-10-1000 by RFX Ltd. UK

[John Moran, Scawby Design]

>Bob said - " A GPSDO with a poor sky view will not do well"

Thanks for the feedback.

I am exactly 100 miles South of Hadrian's wall and a smidgeon West of The Prime 
Meridian. My house is in pretty clear surroundings except for a large willow 
tree in the front garden, which faces South. I can easily mount a pole-mounted 
GPS antenna on the roof above any obstruction on the roof. So, with luck, I 
should have a reasonably clear view, and I can always pollard the Willow ...

Lady Heather was on my 'to buy' list so it sounds as though I should get her 
now and a cheap GPS brick to see what the viewing is like. I have a couple of 
old M12 eval modules from back in the day that were never switched on and a 
couple of uBlox LEA-M8T-0-10 modules chopped out of Huawei PCBs by the Chinese, 
but it will probably be quicker and easier to get a cheap module as you 
suggest. My electronics Lab faces South so I can sit one of the small patch 
antennas that came with the Motorola kit on the window ledge for initial trials 
before climbing on the roof.

>Tom said - "look into Leo Bodnar GPSDO" seconded by Wes.

Thank you both, they look interesting - and low postal charges!

>Hal said "older GPS receivers"

Thanks, that's one of the reasons that I have decided to buy a low-cost device 
rather than try to revive the M12 kits, they are over a decade old.

>Mete - thanks for recounting your experiences, I can see this is a long 
>journey. :-)

>Erik compared rooftop antenna with east window ... sounds like I need to get 
>on the roof, eventually. Thanks for that Erik (sounds like Belgium or the 
>Netherlands?).

John
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[time-nuts] Re: GPSDO - GPS1300-10-1000 by RFX Ltd. UK

[John Moran, Scawby Design]

David - thanks for the reply, but these seem designed for SDR and I wanted 
1pps. Nice and cheap though.

Paul - thanks too; it seems that you are saying that the performance of all 
GPSDOs are the same, but that wasn't the impression I had got from listening to 
discussion here. Fine when the thing is locked (except for sawtooth stuff and 
these hanging bridge things, and digital vs analogue (British) control loops, 
etc.) but what about hold-up performance when it's not.

So, are they all the same ... or not? If they are, why not buy the cheapest 
Chinese device available rather than making your own?

John




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[time-nuts] GPSDO - GPS1300-10-1000 by RFX Ltd. UK

[John Moran, Scawby Design]

With all this interesting talk about -

a) How hard it was to build a GPSDO from scratch and
b) How, to measure a signal accurately, you need a reference circa 10x better

I started to get worried since I want to do both. To help with the latter I 
have acquired an HP5370A that just needs picking up from Scotland, where I was 
hoping to maybe pick up some surplus oscillators as well. But the 10x specs in 
the discussions got me worried enough to look around for a known good GPSDO 
rather than buying a bag-full from China and trying to sort out a good one.

I found this - 

https://www.rfx.co.uk/pdfs/GPS_OCXO_1300_10_module.pdf

and have been quoted £500 as a special deal (they normally have a £1,000 
minimum one-off charge).

Can anyone please pass some sort of judgement on whether its specs are good 
enough to stand in as my master reference until I can find a Rubidium device on 
this side of the pond.

John 
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[time-nuts] Tonga effect on GPS

[John Moran, Scawby Design]

Someone suggested this a while ago, this may be of interest -

https://phys.org/news/2022-02-tonga-eruption-ripples-earth-ionosphere.html

John
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[time-nuts] Time ball clock

[John Moran, Scawby Design]

What a project!

86,400 x 16 foot columns spaced 3” apart arranged on a cylinder 3.9 miles in 
diameter with bigger balls for minutes and bigger still for hours.

Magical, and almost as grand as the 10,000 year clock.

I will raise a Kickstarter Project immediately ...

Seriously though, a small two ball desk-top version would be fun, but you would 
have to silence the thuds a bit.

John
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[time-nuts] Re: A Nice Slice of History

[John Moran, Scawby Design]

The Link worked fine for me, thanks Nigel, just took a while for all those 
pages.

On Page 232 there is information on crystals with two sets of electrodes, 
common on the low frequency bar crystals that I have quite a few of, and a few 
others on this list have a few stashed away.

The following couple of pages are quite interesting and give yet another link 
to a free book for more information - "Electromechanical Transducers and Wave 
Filters" from 1942 which give more information.

The book -

https://archive.org/details/in.ernet.dli.2015.13601

Takes even longer to download because it's coming from The Archive.

Enjoy, and Merry Christmas too.

John


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[time-nuts] Hermetic tantalum capacitors

[John Moran, Scawby Design]

When I was a lad designing telecom kit that had a minimum design life of 20 
years, we used Sprague tantalum cased glass sealed capacitors that were treated 
like gold dust.

Sprague has now been subsumed into Vishay and they still do the same devices, 
stocked by Mouser and Digikey at reasonable prices, so long as you don’t go for 
the aerospace versions.

John
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[time-nuts] Re: in-ground clock room - geophones

[John Moran, Scawby Design]

Poul-Henning Kamp writes:

"There are a number of footnotes about geophones, the primary one being
that they have a resonance frequency in the 4-7 Hz range and therefore
provide no usable information below that.

The second is that it is anyones guess what their sensitivity is,
in particular if you buy it on eBay from somebody who found it
lying in a field after percussive oil-exploration, so buy more
than one."

For something a little more reliable and trustworthy than an eBay gamble,
albeit probably more expensive, there is an organisation that caters for people 
nuts about vibrations -

https://raspberryshake.org/

They offer some very nice products and would allow correlation of time glitches
from pendulums (an interest of mine), and other clocks, with earthquakes and 
other such disturbances.

John
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[time-nuts] Missing links

[John Moran, Scawby Design]

Hello All

Thanks for your feedback.

I now believe it is because I use the digest-mode option to view all these 
e-mails and TVB and JA are having a little trouble with the latest update to 
the system.

I will change to the other option and see if the links re-appear.

John
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[time-nuts] RE - before time was invented (Jan Boutsen)

[John Moran, Scawby Design]

Is it just me, or has something happened to the links to attachments that 
people are adding to their posts?

It used to be that there was a message saying something had been removed, but 
there was then a link at the end of the post to retrieve the attachment.

The 'removed' messages are still there, but the links have been absent for the 
past few weeks.

John

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[time-nuts] Re: Best frequency to start for GHz synth ?

[John Moran, Scawby Design]

Since low phase noise seems to be a main requirement here, this paper by Jeremy 
Everard from York University may be of interest -

'Ultralow Phase Noise 10-MHz Crystal Oscillators'

Available here -

https://ieeexplore.ieee.org/document/8540461

It also shows construction of a double oven system for it.

I believe Jeremy was working on sapphire oscillators 20 years ago when I worked 
at York for a while.

John 
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Re: [time-nuts] Old Crystal.

[John Moran, Scawby Design]

Ref. the original comment about a blue glow seen in a crystal, I would suggest 
that it was simply a blue LED used in exactly the same way that constructers of 
Nixie Clocks add LEDs under the Nixie tubes to make them look more dramatic.

John

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Re: [time-nuts] Daft idea with the National Grid

[John Moran, Scawby Design]

That was some heavy-weight receptionist! :-)

Thanks for the feedback.

John

> On 8 Feb 2021, at 17:58, Poul-Henning Kamp  wrote:
> 
> ----
> John Moran, Scawby Design writes:
> 
>> "If you happen to own something like a steel mill running electric
>> 
>> furnaces or an aluminum refinery, so you can manipulate the load..."
>> 
>> Sometime in the late '80s, my first decent sized computer system came on 
>> line [...]
> 
> We had the same problem when we installed the largest non-university
> UNIX computer in Denmark in the late 1980'ies.  In our case it was
> our heavy-weight receptionist getting into the antique lift, heading
> for the canteen on the top floor.
> 
> -- 
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.

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Re: [time-nuts] Daft idea with the National Grid

[John Moran, Scawby Design]

On Sun, 7 Feb 2021 20:45:57 -0800
Jim Lux said -


"If you happen to own something like a steel mill running electric

furnaces or an aluminum refinery, so you can manipulate the load..."

Sometime in the late '80s, my first decent sized computer system came on line 
at a telecom factory in England. It ran fine for a few days then crashed. 
Rebooting made it run fine for another 7 days then it crashed again, and then 
every 7 days at almost the same time - like a very poor clock. Monitoring the 
mains voltage with an expensive hired monitor showed a huge drop in voltage 
lasting about ten seconds at the relevant time.

It turned out that the biggest steel rolling mill in Europe was only 5 miles 
away and they were testing new motors on the rolls. We had some interesting 
visits and talks with them and persuaded them to turn the motors on one by one 
instead of in batches and, in conjunction with some hefty mains filtering, the 
problem went away.

That sort of load step must have been noticed by the electricity suppliers, and 
half the computers in the city!

John

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Re: [time-nuts] Long Wave Radio-Frequency standard testing

[John Moran, Scawby Design]

There is an earlier NIST publication on the problems here -

https://nvlpubs.nist.gov/nistpubs/jres/64D/jresv64Dn3p239_A1b.pdf

John


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[time-nuts] Technical information on Peltier Modules

[John Moran, Scawby Design]

Following earlier discussions on the pros and cons of Peltier modules for 
temperature control of crystal oscillators, DigiKey have just launched a range 
of small devices. However, the reason for posting that information here is that 
their web page contains a wealth of information on the selection, design, 
operation and reliability of the modules - see here under the Resources heading 
-

https://www.digikey.co.uk/en/product-highlight/c/cui-devices/micro-peltier-modules

John

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[time-nuts] SiTime Stratum 3E DCOCXO

[John Moran, Scawby Design]

Does anyone have any knowledge of the suitability of these silicon vs quartz 
frequency sources for TimeNuts applications?

https://www.sitime.com/products/stratum-3e-dcocxos/sit5721

The published specs seem quite remarkable for a device that is 5 x 7 x 9mm

You have to request a data sheet, which is then for your eyes only, but they 
are quite forthcoming with that.

I have requested a price for a one-off sample and will report back if and when 
they respond.

John
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Re: [time-nuts] SMPS or conventional?

[John Moran, Scawby Design]

From: ed breya 
To: mailto:time-nuts@lists.febo.com
Subject: Re: [time-nuts] SMPS or conventional?

"Regarding TEC life, ..."

A really good reference to TECs, especially factors affecting lifetime is here -

https://tetech.com/faqs/

John 


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[time-nuts] Quantum Time Dilation

[John Moran, Scawby Design]

It's been mentioned many times here that Time-Nuts are continually chasing down 
the more and more esoteric effects that make their clocks less than perfectly 
accurate. I wonder whether any of them have got their clocks to the state where 
corrections to quantum effects are now in their sights?

The paper linked here in Nature Communications explains the upcoming problem -

https://www.nature.com/articles/s41467-020-18264-4

Unfortunately, my mathematical skills are not up to working out the magnitude 
of any errors.

John 


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Re: [time-nuts] What do people use for measuring temperature?

[John Moran, Scawby Design]

Final input from me on this topic.

The surprising, to everyone, result from the research paper referenced in the 
eevblog -

https://www.eevblog.com/forum/metrology/long-term-stability-of-temperature-sensors/?action=dlattach;attach=412153

Was that the cheapest thermistor had a drift of less than 0.5mK/year.

It is the Murata NCP15XH103D03RC and is available from Mouser for 41c. Create a 
cluster of these and you have your low-drift reference.

John 


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Re: [time-nuts] What do people use for measuring temperature?

[John Moran, Scawby Design]

Thanks for going easy on me Bob ... a case of more haste, less speed! I 
focussed on low long-term drift specs without realising I had turned up a 
voltage reference, sorry.

However, I have found some YSI glass encased thermistors that have long-term 
drift specs of <10mK at 25C and 75C over a period of 100 months. They are in 
the YSI 46000 series - data sheet attached.

http://www.farnell.com/datasheets/169207.pdf

There is an interesting paper by NIST on achieving the International 
Temperature scale - link attached (it is 196 pages and 10MB) that seems to 
indicate platinum sensors are the most stable at less than 1mK and, of course, 
to be able to measure these resistors accurately, you need an equally low-drift 
voltage/current source. :-)

https://nvlpubs.nist.gov/nistpubs/Legacy/TN/nbstechnicalnote1265.pdf

This reference appeared from an EEVblog where I think some Volt-nuts were 
discussing temperature. One of them confirmed that the most economical way was 
to have a group of lower-cost sensors and characterise them.

https://www.eevblog.com/forum/metrology/long-term-stability-of-temperature-sensors/

John 


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Re: [time-nuts] What do people use for measuring temperature?

[John Moran, Scawby Design]

Would not a band-gap temperature sensor such as the LT6657 be better than a 
thermistor for precision, low drift applications?

The above device has 30 ppm/√kHr long-term drift. That should hold a mk for a 
fair few years.

John 

https://www.analog.com/media/en/technical-documentation/data-sheets/6657fd.pdf



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Re: [time-nuts] Precise Pendulum

[John Moran, Scawby Design]

Interesting ...

They quote - “At the other end of the scale, gravity dominates over very long 
distances, while quantum effects vanish entirely at these distances.”

I thought quantum entanglement was valid over any distance - Einstein’s “spooky 
action at a distance”. Thus offering the possibility of instantaneous transfer 
of information over stellar distances.

This is one of the problems they are trying to sort out with the 
incompatibility of the two conflicting hypothesis.

To then dismiss one of the ‘strange’ properties of quantum mechanics where 
there is an apparent overlap, right at the beginning, seems a bit strange.

John
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Re: [time-nuts] ThunderBolt question

[John Moran, Scawby Design]

Everyone ...

I must admit to being amazed at the cavalier attitude to impedance matching. I 
dread to think what a state we would be in if the original telecoms networks 
were designed with such disregard.

OK, my background is in the old telecoms - land-line stuff where we had a 
variety of impedances to work with, balanced and unbalanced, but mainly 600 
ohms for the audio and line side and 50 or 75 ohms for the internal stuff. But 
whatever we were working with, designing to match the impedance closely was a 
critical parameter, and not difficult at all. Regarding connectors, you could 
mix and match types as long as everything you used was designed to match the 
same impedance and terminate the cable properly.

When you are designing amplifiers to be flat within 0.1dB over a wide 
bandwidth, impedance matching matters both for steady-state amplitude settings 
and ringing caused by the reflections.

There is a whole discipline around transmission lines going back nearly 200 
years, for a reason.

OK, TimeNuts tend to be piping single frequencies around the place, but I 
thought this was a place looking for precision, and playing with low-level 
signals, and hunting down esoteric artefacts and anomalies. Wading roughshod 
through transmission theory is at odds with that for me, sorry.

It's not as though designing stuff to have the right input and output 
impedances is difficult. Nowadays with integrated amplifiers you can just use 
the brute-force method of hanging a 50 ohm resistor across a 'high-impedance' 
input and another 50 ohm resistor in series with a 'zero ohm' output impedance. 
Back in the day we designed them to inherently have the right input and output 
impedance and so saved throwing lots of signal away.

My humble apologies for the rant ... but I just couldn't believe what I was 
reading this morning when I opened the mail.

I guess I'll get thrown out for this ...

John

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Re: [time-nuts] TICC / TimeLab fun

[John Moran, Scawby Design]

Chris

I don't have any of that kit yet but it seems to me that the two units have 
locked to each other somehow, a bit like the question I raised a while ago 
about crystals locking to each other.

Just a pure guess though.

John
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Re: [time-nuts] Vaperware Parts and pulse stretching circuits

[John Moran, Scawby Design]

Date: Fri, 24 Apr 2020 23:19:24 + (UTC)
Perry Sandeen said -


"I believe It is a bit disingenuous to say: *It is a small-pitch device but not 
impossible to solder*.

Really?? If you've dropped $750 to $1K for a stereo microscope and other 
specialized soldering equipment then you can probably do it without too much 
difficulty.? Or some may access to such specialized equipment.

But for us *Po Folks* hobbyist we have to stick with older but larger parts."



Just to put the record straight, I am a 72-year-old retired electronics 
specialist who uses a 50-year-old Weller soldering iron and a magnified (x3.5) 
bench light to solder 64pin 0.5mm pitch MSP430 microprocessors by hand. As I 
said - "... not impossible to solder."



Like you Perry, I am a *Po Folk* :)



Kind regards - John


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Re: [time-nuts] Using speaker / earphone for PPS testing (not a question)

[John Moran, Scawby Design]

Bob kb8tq - Wed, 22 Apr 2020 07:46:34 -0400

Said -

>
A lot also depends on what sort of voltage / power the speaker is expecting. 
If it's a high impedance voice coil gizmo things aren't going to be as easy as
with a piezo gizmo designed to work in a 1.3V battery powered greeting card. 

Where did I leave that 10KV output amplifier ?.. should be easy to find ?. :)
>

10kV may be a little excessive for normal devices and ears.

However, Texas Instruments make some rather nice piezoelectric haptic drivers 
that include an on-chip boost voltage generator that can supply up to 200v to 
drive the piezo disc ... more than enough to drive someone mad after a few 
hours of 1PPS ticking in the cellar. The device is a DRV8662 and is available 
from Digikey for $3.35. It is a small-pitch device (0.5mm) but not impossible 
to solder.

I will order a couple and see how they perform. I think I have some 4kHz 
resonant piezo discs that should ring quite nicely ... even when hit by a 
narrow pulse ... at 200v.

Data sheet here -

http://www.ti.com/lit/ds/symlink/drv8662.pdf

There are a couple of other information sheets referenced at the end of the 
data sheet.

John 


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Re: [time-nuts] OCXO and fluctuations after EFC adjustment

[John Moran, Scawby Design]

On Fri, 10 April 2020 14:31:53 -0700 Rick wrote:


>At this time, I will give my usual speech about IMHO the fact that

>since the invention of the DDS on a chip, EFC should no longer be used

>for high performance oscillators.

During my 50 years in the electronics industry I have always been puzzled about 
one aspect of crystal oscillators. They go to great lengths to use a precise 
piece of quartz as the heart, because of its unique properties, and then add 
standard external components - capacitors, varactors, Zeners, etc. to tweak its 
frequency. All these components vary far more than the original piece of quartz 
... hence my confusion.

I know it is practically impossible to grind a crystal to exactly the frequency 
you want, and it then drifts over time, but what is the logic of using 
relatively wildly varying components to adjust the quartz? Are their 
temperature and ageing characteristics swamped by the superior crystal?

In all the papers I have ever read, the subject is never mentioned ... you just 
add a variable capacitor and/or an EFC circuit and job done.

I guess this is showing my total ignorance here, but I would like to know.

Maybe this is at the heart of Rick's usual speech?

John


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[time-nuts] Facebook, the master of Time

[John Moran, Scawby Design]

I just stumbled across this and wondered what people thought of it.

https://www.popularmechanics.com/science/a31746495/facebook-time-synchronization-breakthrough/

John

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Re: [time-nuts] Synchronisation of crystal oscillators

[John Moran, Scawby Design]

Since the answer to my original question of possible synchronisation was a 
reasonably resounding no, I started doing some design work and then got an 
off-post message from TVB suggesting the use of his neat PicDiv chips to divide 
all my crystals down to 1PPS.

On ordering a batch he came up with an even better idea - instead of using 
separate oscillators and dividers, how about trying to use the oscillator 
circuitry built into micros to drive the crystal and then program the micro to 
divide it down to 1PPS (and also output a buffered crystal signal on another 
pin). So, I will be looking at using MSP430 micros to perform this trick and 
keep you informed of progress.

Obviously, this isn't a hyper-precision TimeNut type 1PPS but it should all 
look interesting and may show whether synchronisation can happen or not at 
these low frequencies.

Plus, some of these crystals were classed as Master crystals in their old 
Telecom days so when I finally arrange to pick up my HP5370A from gandalf9 I 
will be able to see how they perform. I will let you know.

John

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[time-nuts] Synchronisation of crystal oscillators

[John Moran, Scawby Design]

My apologies if this is slightly off-topic, but it does concern crystal 
oscillators.

I have a small collection of ancient crystals amassed over the past 50 years or 
so. Half a dozen are low frequency (3,600Hz, 10kHz,  and 100kHz), long bar, 
crystals sealed into B7G vacuum tube bodies. I was considering mounting them 
all in a neat row in a nice aluminium housing with individual oscillator 
circuitry and LDO regulators to ensure that they were all independent. For fun 
I will divide each oscillator down to 1PPS and use that the flash individual 
LEDs in the face of the housing, and watch them all slowly move in and out of 
phase with each other.

However, I then remembered Huygens's discovery that 1S pendulums mounted on the 
same wall, or beam, would synchronise and swing either in phase, or out of 
phase and sometimes one would be stopped, by the minute interactions.

So, my question is - will my row of low frequency crystals 'talk' to each other 
and synchronise in their frequency groups as well? Remember that these crystals 
are long thin bars of quartz - one of the 3,600Hz crystals being 2mm square by 
60mm long - so they will possibly vibrate quite vigorously compared with squat 
discs.

I look forward to your comments.

John
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Re: [time-nuts] What is the BEST crystal?

[John Moran, Scawby Design]

Wow, that provoked an interesting discussion!

Thanks for all the information and references to further information - it 
should keep me quiet for a while.

Interestingly 50mm diameter was about the diameter of the crystals used by the 
British Post Office in the early days for generating a master oscillator. It 
wasn't ground into a plano-convex lens but as a ring and was about 10mm thick. 
Like the old WW2 crystals the electrodes weren't plated but just contact rings. 
I have no idea what frequency they were ... by the time that I realised they 
were scrapping all this kit it was gone and I only managed to salvage two GPO 
Type 36 master 1S pendulums from a dumpster!

Thanks again for all the feedback.

John
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[time-nuts] What’s the BEST crystal?

[John Moran, Scawby Design]

Since the poor old SC cut crystal has been given such a kicking for its 
inconvenient placement of spurious responses, is there a better, or BEST 
crystal for putting in an oven and turning into a nice reference?

John

Cheers - John

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[time-nuts] Oven Controlled Voltage Controlled SAW Oscillators

[John Moran, Scawby Design via time-nuts]

Do these devices have any use in the TimeNuts community?

https://www.electronicsweekly.com/news/products/digital-integrated-circuits/iqd-launches-ocvcsos-2020-02/

They claim lower phase noise and noise floor and jitter.

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[time-nuts] PLL synthesizer information from TI

[John Moran, Scawby Design]

For those of you interested in exotic Phase-lock Loop synthesizers, I just 
received this information from TI -

http://e2e.ti.com/blogs_/b/analogwire/archive/2020/02/10/why-component-integration-carries-weight-for-space-based-pll-synthesizers

The web page includes a link to an application note with more data on their 
highly integrated solutions enabling designs from 10MHz to 20GHz.

The parts aren't cheap, but they are designed for space applications.

I have no links with TI except for having used their devices for over half a 
century.
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[time-nuts] Construction and shielding information

[John Moran, Scawby Design]

Gerard

Thanks for the cornucopia of information, much appreciated.

Cheers - John

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Re: [time-nuts] Power supply for time source concerns

[John Moran, Scawby Design]

Date: Mon, 23 Dec 2019 07:51:49 -0500

From: Charles Steinmetz mailto:csteinm...@yandex.com>>

To: time-nuts@lists.febo.com

Subject: Re: [time-nuts] Power supply for time source concerns

Message-ID: <5e00b865.4000...@yandex.com>

Content-Type: text/plain; charset=utf-8; format=flowed



Charles wrote:



[...  To get even that far, one needs multiple

shielding (see list member Gerhard Hoffman's construction photos for

ideas) and may very well need PC boards with more than two layers.]


Being a relative newcomer here, how do I search the archives for a specific 
author's input? I found some random posts from Gerhard but I don't see how to 
search for all of his input to find these construction photos.

Sorry to be so dim.

Regards - John
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Re: [time-nuts] gpsdo 10MHz steering resolution

[John Moran, Scawby Design]

Bob

This based in Germany, 50Hz mains, hence my thoughts.

John

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Re: [time-nuts] gpsdo 10MHz steering resolution

[John Moran, Scawby Design]

I may be completely wrong here but if the span of that spectrum is 1kHz, then 
the spurs look like 100Hz mains hum   frequency modulation of the 10MHz.


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[time-nuts] Bulk Acoustic Wave (BAW) technology

[John Moran, Scawby Design]

Just been sent information on this technology by TI. Is it of any use/interest 
to TimeNuts?

https://training.ti.com/introducing-tis-bulk-acoustic-wave-baw-resonator-technology

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Re: [time-nuts] new WWVB BPSK dev board

[John Moran, Scawby Design]

Good morning

I agree that 1deg is overkill but I was simply extrapolating one extra decade 
from BOB kb8tq's "backing off a bit" comment where he got down to 10deg. :-)

10MHz is an obvious sample rate - sorry, that fell into a blind spot here!

I think I will get distracted over Christmas sketching out some designs ...

Thanks - John

-Original Message-
From: Poul-Henning Kamp [mailto:p...@phk.freebsd.dk]
Sent: 4 December, 2018 11:03 PM
To: Discussion of precise time and frequency measurement 
; John Moran, Scawby Design 
Subject: Re: [time-nuts] new WWVB BPSK dev board


In message 
mailto:am0pr03mb4129fbd0922805fc14b8cefde4...@am0pr03mb4129.eurprd03.prod.outlook.com>>,
 "John Moran, Scawby Design"
 writes:

>However, fast A-Ds are not particularly cheap and you would need circa
>50MHz sample rate to resolve 1deg of the carrier, and TVB has already
>stated that there are no time benefits to BPSK, so this is all just an
>interesting technical exercise, isn't it?

I admit it would be interesting to do the allan variance on it, but measuring 
the carrier to 1 degree in every single cycle is way overkill.

1 MHz sampling rate is fine, but go for 5 or 10 MHz so you can drive the ADC 
directly from your house-standard.

And BPSK *does* improve the timing, because you can very precisely measure when 
the change of phase happens, and it since it happens at a carrier zero-crossing 
you can filter it down to +/- sample.

--
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org<mailto:p...@freebsd.org> | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

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Re: [time-nuts] new WWVB BPSK dev board

[John Moran, Scawby Design]

I'm a little puzzled as to why people keep calling 60kHz - 'RF'. Many Hi-Fi 
audio amplifiers go higher than that.

As for an 'RF' front end, there are dozens of off-the-shelf op-amps that can 
amplify the signal from a tuned ferrite rod aerial sufficiently to then feed 
into a decent A-D and then a micro.

Analog Devices have A-Ds that digitize the carrier of 12GHz RF signals so I 
think we should be able to manage 60kHz ... the problem then being to process 
the resulting data stream.

However, fast A-Ds are not particularly cheap and you would need circa 50MHz 
sample rate to resolve 1deg of the carrier, and TVB has already stated that 
there are no time benefits to BPSK, so this is all just an interesting 
technical exercise, isn't it?

John Moran
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