Hi

The interference “front” turns out to be over the US rather than over the UK. Power,
distance, and propagation all get into the “why”. The answer is that you get crazy
fades and phase shifts as a result.

Bob

Hi thank you Bob for the mail

Do you realise the 60 Khz Transmitter in the UK was moved from Rugby in the
centre of England north by more than 200 miles
Paul

-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces@lists.febo.com] On Behalf Of Bob
kb8tq
Sent: 04 December 2018 02:38
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] new WWVB BPSK dev board

Hi

The interference "front" turns out to be over the US rather than over the
UK. Power,
distance, and propagation all get into the "why". The answer is that you get
crazy
fades and phase shifts as a result.

Bob

https://universal-solder.ca/product/everset-es100-cob-wwvb-60khz-bpsk-receiv

with

news.

http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com

time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

No virus found in this message.
Checked by AVG - www.avg.com
Version: 2016.0.8048 / Virus Database: 4793/15883 - Release Date: 08/14/18
Internal Virus Database is out of date.

that address is incorrect:  Website: www.EversetClocks.com

Alex

On 12/3/2018 6:20 PM, Paul Bicknell wrote:

I am on the east coast and the everset chips work very well I have had a
unit for musty be 5 years and ran tests for them. So at least here in
Boston it does very fine.
Hope that helps.
Regards
Paul
WB8TSL

On Mon, Dec 3, 2018 at 10:33 PM Alex Pummer alex@pcscons.com wrote:

This seems relatively expensive for a little wirebonded board of this type.
It seems like the sort of thing that you would normally find on aliexpress
or ebay for a few dollars.

It it because the es100 is otherwise unobtanium?

Eric

On Mon, Dec 3, 2018, 6:12 PM Tom Van Baak <tvb@leapsecond.com wrote:

I assume thats exactly the case. I also thought it was pretty high.
The actual clocks are about $50 or less I believe. So the board seems a bit
off.
Regards
Paul
WB8TSL

On Tue, Dec 4, 2018 at 12:03 AM Eric Garner garnere@gmail.com wrote:

$69 CAD is roughly $50 USD.

Expensive for what it is but easier to work with than gutting a working clock and no more expensive.

I ordered one.  Curious to see what sort of precision we can get from an i2c interface.

If nothing else I suppose I can toss a six digit i2c 7 segment module at it and roll my own WWVB desk clock.

—msa

Majdi good for you. You will have fun. OK precision thats a slippery slope.
The documentation will indicate the sequence time and length and as I
recall the chip produces a result every 90 seconds using the long phase.
There is a short phase after you have acquired that is something like 30
seconds. But I recall it was tricky aligning to the second. That was the
BPSK edge. Anyhow it does work.
I hear they ship some arduino code with it. That would be fun to look at. I
used whats was called a SXB at the time. Worked fine.
Regards
Paul

On Tue, Dec 4, 2018 at 11:26 AM Majdi S. Abbas msa@latt.net wrote:

Thanks for the heads up Tom! I ordered one and if it comes before the end
of the year I may have some time over the holidays to do acquisition test
from Maryland and maybe some cross-comparison with GPS PPS.

Here in Maryland I have somewhat unreliable reception on commercial
non-BPSK WWVB clocks at my house. My Casio Waveceptor watch is 99%+
reliable when I'm asleep on the 2nd floor but much less likely to work in
the basement. I can reliably hear the amplitude-keyed WWVB carrier on a LF
receiver with a homebrew loop (about 3 foot by 3 foot) in the evenings but
it takes some imagination to think I can hear it during the daytime.

Tim N3QE

On Mon, Dec 3, 2018 at 9:12 PM Tom Van Baak tvb@leapsecond.com wrote:

Hi

The I2C clock rate is going to matter a bit in terms of what you can achieve.
Since the device is targeted at low power, the max practical baud rate may
not be very high. I2C can have a lot of wait in it ... There are a lot of registers
dumped after each “reception attempt”.

There also is the basic question of how the IRQ flag relates to the time the
chip “sees”. If it’s actually WWVB time sync’d then that’s a useful thing.

None of this is likely to be an issue in a wall clock. If they can run at a “tens of ms”
sort of level that’s more than good enough. We really want to get to microseconds
don’t we :)

Bob

It does a very good job of pulling the signal out of the noise.  It
works in NH, traditionally a fringe region, in all but the most shielded
of rooms.  I also had occasion to test it for Everset in Kangerlussuaq,
Greenland.  I found it had no trouble acquiring at any time of the day. 
If the ES100 does not do well enough for you, there is supposedly an
ES200 available that uses a longer sequence for even more sensitivity.

The one thing I wish is that there were access to the synchronized
analog signal and/or a 1PPS.  Even a top of the minute would be useful. 
It only has the I2C digital interface.

73,

David N1HAC

On 12/4/18 11:35 AM, Tim Shoppa wrote:

I understand why a low-volume shipment of what started as a board costing a
few pennies costs $50, but does that simply mean that low-cost parts aren't
the right answer for this sort of application ?

How would an SDR based on a raspberry pi zero, a suitable ADC and a tuned
rx circuit compare ?

On Tue, Dec 4, 2018 at 4:54 PM David G. McGaw David.G.McGaw@dartmouth.edu
wrote:

Because of the Q of WWVB's transmit antenna (at least 300 by my back of the
envelope estimates), I don't think we could ever claim a WWVB PPS edge
sharper than 5 milliseconds and that might be optimistic.

Tim N3QE

On Tue, Dec 4, 2018 at 11:49 AM Bob kb8tq kb8tq@n1k.org wrote:

I ordered one, too.  It looks like there's an IRQ line that goes low +/- 100 ms of the second mark.  It will be interesting to see how stable that is in real life.

On Dec 4, 2018, 11:27 AM, at 11:27 AM, "Majdi S. Abbas" msa@latt.net wrote:

On 12/4/18 8:59 AM, Adrian Godwin wrote:

"suitable ADC" and "tuned Rx circuit" would greatly interact.. the more
narrow band your Rx, the fewer bits you'd need in your ADC - The Teensy
($20 arduino clone) can sample at well over 100ksps with a 16 bit (13-14
ENOB) differential input, and I'll bet you could make a simple PSK
demodulator in software, either on the Teensy or on the host PC  (which
could be a RPi or Beagle) connected via USB.

https://www.pjrc.com/store/teensy32.html

They also sell a higher performance audio interface that might be useful:
https://www.pjrc.com/store/teensy3_audio.html
Although it's 44.1 kHz sample rate - but might actually support other rates.

So the real question is where can you find an inexpensive 60kHz front
end amplifier.

The computer (whether arduino, teensy, beagle, or Rpi) isn't the
limiting thing, it's the RF to digital interface. -

Find a $20 60kHz narrow band receiver/ADC , and the rest is straightforward.

On 12/4/18 9:00 AM, Tim Shoppa wrote:

Sure you can.. you do a matched filter to the waveform, so you're not
just looking at a single zero crossing or cycle.  Getting fraction of a
degree phase accuracy from a strong signal is entirely possible.

A Q of 300 implies a bandwidth of 200Hz, which would, if a single
section, be a delay of a few milliseconds.  But that delay should be
constant. What might be the limit on precision is whether the delay
through the antenna and the ultimate radiated phase changes with, say,
temperature or soil properties.

In message CALiMYrs1kW3SwUTUpKrauhc3o=ODR7HXix3yHva=LB+wS83cEw@mail.gmail.com
, Adrian Godwin writes:

You can do a LOT more fun stuff that way, and it isn't even hard.

If you clock a 1MSPS ADC from an OCXO you can discipline it to whatever
VLF signal you prefer (or an ensemble of them)

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@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.

In message 6718818b-5243-8ad1-ddbd-6115fcdb6c29@earthlink.net, jimlux writes:

See also:  Loran-C ?

And with the new phase modulation, you can do get down in low
microseconds at tau=1, but the atmosphere will ruin longer taus.

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@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.