On Thu, 29 Mar 2018 03:12:24 -0700
Hal Murray hmurray@megapathdsl.net wrote:

I think the easiest is GnuRadio... A quick googling lead
to https://github.com/jasonabele/gr-wwvb
I don't know anything about it so use at own risk :)
But at least it seems like something that can be done easily
on a rainy evening.

Normal RTL-SDR's do not work for WWVB as they have a lower cut of
frequency in the range of 20-50MHz...unless you bypass the tuner
chip and feed the signal directly to the ADC. As IIRC all RTL-SDR
give you something like 2Msps, that should be more than plenty to
decode WWVB and related signals. If you feed the RTL-SDR from an
external frequency source, you should be able to related that
frequency source to WWV.

		Attila Kinali

--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson

It does not take a fancy receiver to hear WWV or CHU. Any super low end shortwave portable (less than $100) will do fine.

You then feed the audio into a PC with naps configured for NTP audio refclock.

The wideband USB connected DSP receivers are neat and I am using one for various purposes in the shack but not yet WWV. You would have to characterize one and it’s computer based DSP processing for latency.

Any such setup has to be characterized for latency (propagation + receiver+ soundcard) anyway. Sub-millisecond accuracy is a reasonable goal.

In continental US, one or more of the three 5/10/15 MHz WWV signals is receivable most any time of day. NTP WWV software knows how to cycle one particular model of receiver through the frequencies and can easily be modified to work with other computer-controllable receivers.

WWVH can be reliably heard for some of each day as well.

A recent QST or QEX had a nice simple 10MHz WWV receiver in it. I think it was oriented towards extracting 10MHz carrier and not for demodulating the time code, however.

Tim N3QE

Hi

If you are running 10 MHz as your lab standard, you will have 10 MHz floating around.
Add to that various 10 MHz OCXO’s here or there on the bench and you have even more
odd stuff right at 10 MHz. Yes, if you run triple shield coax for your standard lines and your
antenna is 1000’ from your lab, this may not be that big an issue. If you setup is a bit more
modest, as WWV fades, the local stuff will be apparent. Bottom line - consider 5 MHz  (
unless you are set up with that as your standard ….).

Bob

On 3/29/18 3:12 AM, Hal Murray wrote:

Hal,
you should know better than to have a question like "get time" on this
list without specify the precision and accuracy <grin>.....

I was in a meeting yesterday with a lot of technical people, discussing
testing an HF receiver, and I mentioned WWV as a source, and there were
a combination of blank looks and amused/amazed looks (at the blank
looks) - OK, so now we know who in the room are the computer only people
(WWV? is that some sort of NTP protocol?) and who  are the radio people

The little HF dongle receivers will certainly receive HF WWV or WWVH, if
propagation supports it, and you can listen to the dulcet tones of the
appropriately gendered announcer ("at the tone, the time will be twelve
hours thirty four minutes coordinated universal time") - you could
probably track and decode the tone/ticks.  I would think that if you can
hear the voice, you can decode the 100 Hz subcarrier, but I've not tried
it. You can see the 100 Hz on a spectrum analysis display.

I would think that you can get propagation limited accuracy with the
RTL-SDR type receiver.

Antenna is going to be the big challenge - the little whip antenna for
the dongle won't usually cut it.

On 3/29/18 3:49 AM, Attila Kinali wrote:

The RTL-SDR is an interesting device - I'm putting together a hobby HF
interferometer with GPS to provide time tags.

Yes, most of the newer parts (RTL-SDR v3, for instance) provide a
programmable bypass of the front end downconverter (the part is actually
designed to tune TV signals and the L-band output of a consumer dish LNB)
The backend chip (RTL2832U) is a digital downconverter which mixes and
filters the nominal 3.5 MHz IF which is sampled at 28.8 MHz

You can actually adjust the output sample rate - something around 2
Msample/second is the default, but there's lots of other rates
available.  For WWV you could crank it down, but..
The ADC is 8 bits (7 ENOB) and the output is 8 bit I/8 bit Q.

Folks have modified the RTL-SDR to accept an external frequency
reference, so you could take the output from your ensemble of Cesium
references to discipline a hydrogen maser (so your close in phase noise
is better),then use that to drive a 28.8 MHz discrete divide/multiply
chain, and run that into your $30 receiver to improve the frequency
accuracy.  (not for nothing are we called time-nuts)

Hi

There are a lot of HF receiver gizmos out there these days. Is $5 to much to spend?
Does the budget make it up to $300? Do you want to pick up every time transmission
at once? (as constrained by propagation).

For something like 5 MHz / 10 MHz WWVB plus CHU, there are $20 demo boards that look like
they would do the trick as.a direct sampling device. I haven’t tried one yet. I have no idea
how well they actually do.

My guess is that at HF, propagation will limit the usefulness of the carrier as a stable
signal. Anything that will drift less than a few 10’s of Hz is going to do fine to pick up the audio.
That’s not all that crazy hard at 10 MHz.

Once you do get the time ticks off of the audio, you still have a “millisecond” level accuracy
signal due to propagation. You also have a signal that will drop out from time to time ( unless
you live in Colorado).

Bob

I'll add to the conversation. CHU is easier to deal with because its not a
subcarrier as the 100 Hz WWV signal is.
Its FSK and bell 103 modem style.
Regards
Paul
WB8TSL

On Thu, Mar 29, 2018 at 10:08 AM, jimlux jimlux@earthlink.net wrote: