Valentines Day & Love Numbers
The randomness of WWVB propagation require incredibly long measurements
to get an interesting degree of accuracy compared to a GPS driven solution.
The WWVB signal does respond nicely to solar flares if measurements are
integrated
over one minute. Check out the VLF monitoring stuff on my web page.
On 02/21/2014 12:06 PM, John Seamons wrote:
As a starting point: Here's an extension of the SAQrx PC sound card receiver that supports 192 KHz sample-rate sound cards. Enough to get you WWVB.
https://sites.google.com/site/swljo30tb
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--
Chuck Forsberg WA7KGX caf@omen.com www.omen.com
Developer of Industrial ZMODEM(Tm) for Embedded Applications
Omen Technology Inc "The High Reliability Software"
10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430
I was monitoring WWVB against a good local standard and evaluating 60kHz
'seeing' 30 years ago. Sometimes it is beautifully quiet, after a storm
front went through as I remember, at other times it's absolute hash... to
the point that the HP 117A would not even hold lock.
-John
=================
The randomness of WWVB propagation require incredibly long measurements
to get an interesting degree of accuracy compared to a GPS driven
solution.
The WWVB signal does respond nicely to solar flares if measurements are
integrated
over one minute. Check out the VLF monitoring stuff on my web page.
On 02/21/2014 12:06 PM, John Seamons wrote:
As a starting point: Here's an extension of the SAQrx PC sound card
receiver that supports 192 KHz sample-rate sound cards. Enough to get
you WWVB.
https://sites.google.com/site/swljo30tb
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
--
Chuck Forsberg WA7KGX caf@omen.com www.omen.com
Developer of Industrial ZMODEM(Tm) for Embedded Applications
Omen Technology Inc "The High Reliability Software"
10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
On 2/20/14, 8:51 PM, Bob Camp wrote:
Hi
You can get parts in the 18 bit and up range for not a whole lot of money with rational sample rates for a WWVB receiver. Analog Devices and Linear Tech both make some interesting looking parts. They get you into the >=100 db dynamic range area.
Yes. 192ksps is considered audio and is now available as a common part
for consumer devices. Or go with a 1-bit part and then decimate the hell
out of the result.
Even with a lower bit count part, you pick up some bits in the downsampling process. As long as you have enough noise to keep things moving, you can track pretty far down into the crud. GPS receivers do that sort of thing all the time.
Since this is slow audio after the CIC decimator, things like ARM chips probably have enough DSP horsepower to do what you need to do. The decimator it’s self is not terribly taxing if you don’t go too crazy with the rate change.
This all makes more sense to me than hacking a bunch of op amps and
filter hardware. Use a low bit-depth but fast part then decimate. If it
is fast enough you can get by with very simple anti-alias filtering.
Like you said, if you have enough noise to randomize the LSB you are
good to go. I bet that the AMBCB provides more than enough randomization
power. And if it doesn't, just inject enough broadband noise to
randomize the LSB. The rest is just SMOP.
Just for giggles I took a look at the output of the ADC on my Hermes
board. The input is my Pixelsat loop which is broadband from 50kHz to
30MHz. (It has significant output down to below 20kHz.) The ADC of my
Hermes HPSDR board is being fed with the raw output of the antenna with
no filtering so the ADC is seeing everything from DC to 60MHz that comes
out of the antenna. Peak ADC level at my location is -40dBFS. I live
about 35km N of San Antonio so my location is neither particularly RF
quiet nor noisy. Seems like the 16-bit ADC has plenty of headroom. I
hear WWVB very handily on this setup and I am seeing -83dBm out of my
antenna for WWVB on peaks. (Actually the S:N is pretty good at over 16dB
in a 300Hz bandwidth.) This is near noon local time.
--
Brian Lloyd, WB6RQN/J79BPL
706 Flightline Drive
Spring Branch, TX 78070
brian@lloyd.com
+1.916.877.5067
On 2/20/14, 10:35 PM, Graeme Zimmer wrote:
I have a Kenwood TS-940S transceiver that can receive 60 kHz but I
have never heard anything
Where are you? It must be deaf as a post.
Most ham receivers that purport to have coverage down there really
don't. I thought my Flex 5000 should hear that handily but all it ever
heard were images of the AM-BCB. The HPSDR Hermes board in my ANAN-10
hears WWVB a treat. Direct Down Conversion (DDC) is your friend and
anyone considering playing with this stuff really needs to be thinking
about a DDC receiver.
--
Brian Lloyd, WB6RQN/J79BPL
706 Flightline Drive
Spring Branch, TX 78070
brian@lloyd.com
+1.916.877.5067
Sorry for comming late to the party...
This may be relevant:
http://phk.freebsd.dk/loran-c/CW/
The basic idea is that you use a high-rate ADC, something like 1MS/s
and then you average into for instance a 1msec = 1.000 samples circular
buffer.
That gives you a very narrow comb filter for all frequencies which
are a multiple of 1 kHz, and extracting the phase from, for instance
the 60 kHz WWVB carrier will be trivial.
In the example above, the buffer were w full second long, 1.000.000
samples, this reveals the per-second modulation of the carrier, and
allows you to extract any (averaged) signal on an integral Hz carrier
frequency.
There are Arm chips out there now with 1MSPS*12bit ADCs that's
plenty for this kind of stuff. (see also: http://phk.freebsd.dk/AducLoran/)
--
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.