On 15/09/2023 14:43, john.haine--- via time-nuts wrote:

Yes, I can confirm reception in Edinburgh using a Youloop antenna in an
attached garage.

So, is there any sort of software decoder for the signal?  I don't have a
specialised hardware receiver, just the usual SDR boxes including an Airspy HF+
Discovery.

Thanks,
David

SatSignal Software - Quality software for you
Web: https://www.satsignal.eu
Email: david-taylor@blueyonder.co.uk
Twitter: @gm8arv

David
There have been various things posted in the past that have required A/Ds
and such. Poul here on Time-nuts did a semi software version. (I think) But
the fact is the old LORAN C receivers for frequency are a great way to go.
The only difference between LORAN C and eLORAN is the 9th pulse used as a
data channel. There was no 9th pulse in the old LORAN C. I have not seen
anything that describes the coding. It may be out there but I haven't been
interested in that. For many of us its an alternate very accurate Cesium
referenced source.
How it all develops if the governments supports it will be pretty
interesting. Certainly the old positioning is possible. The data channel
can provide propagation behaviors to allow for very accurate time and
positioning. The new generation receivers will all be SDR based.
I have actually seen an operational prototype numbers of years ago.
Regards
Paul
WB8TSL

On Sun, Sep 24, 2023 at 11:04 AM David Taylor via time-nuts <
time-nuts@lists.febo.com> wrote:

Hi

The issue with doing this with a low cost SDR board is not so much receiving / demodulating the
signal. It’s a pretty good bet somebody out there has been there / done that. The issue is pulling
an accurate “time pulse” out of your typical SDR setup.  This is a  somewhat unusual thing to want
to do. Finding a “stock” setup on a low cost board that does this will be a bit of a challenge.

Bob

One word - UrsaNav.

Kind regards,

John

https://linkedin.com/in/john-h-6a131b12/

I agree.  Most inexpensive SDRs, and more particularly, the gnuradio or other software, tends not to be designed for deterministic timing.  It is true that you can run some tests and empirically determine the delay through the software, but then, you have to worry about the non-deterministic behavior of the host OS. 

Typically, what you’d need is to simultaneously grab a counter running off the sample clock AND the ADC samples (presumably decimated in the hardware), and then you can deal with the uncertainty, and generate a count that can be compared against that same counter to generate an output pulse.  Most of the SDR hardware out there uses one of the multitude of chips that implements some form of pre filtering and decimation and post filtering - but those are typically deterministic in delay.  It’s everything after the interface to the host processor that’s non deterministic.  

Now, if you’re implementing the SDR on a dedicated processor, with no OS, and careful use of interrupts, you can do it.  But that’s what commercial timing receivers do. 

On Sun, 24 Sep 2023 12:38:34 -0400, Bob Camp via time-nuts time-nuts@lists.febo.com wrote:

Hi

The issue with doing this with a low cost SDR board is not so much receiving / demodulating the
signal. It’s a pretty good bet somebody out there has been there / done that. The issue is pulling
an accurate “time pulse” out of your typical SDR setup. This is a somewhat unusual thing to want
to do. Finding a “stock” setup on a low cost board that does this will be a bit of a challenge.

Bob

time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
 

If I may disagree, the only part that matters when generating a timing information
from a SDR is the knowledge that not a single sample is lost in the periodic acquisition
by the ADC, and the time information encoded in the received message. Since both
information propagate through the asynchronous processing chain at the same rate, they
end up being decoded simultaneously and can be compared with each other to adjust e.g.
the clock of the ADC which also acts as the source of the 1-PPS generator. This is at
least what we did in http://jmfriedt.free.fr/ifcs2021.pdf: our initial error in this
investigation was indeed to try and steer the GP-CPU clock and use it to generate the
timing information, when the only deterministic part of the processing is in the FPGA
clocking the ADC.

Best, Jean-Michel

https://forum.pjrc.com/threads/45693-A-second-T31-Precision-Frequency-Standa
rd

On the second page of the thread he posts his Teensy code.

John.
-----Original Message-----
From: David Taylor via time-nuts time-nuts@lists.febo.com
Sent: Sunday, September 24, 2023 2:15 PM
To: time-nuts@lists.febo.com
Cc: David Taylor david-taylor@blueyonder.co.uk
Subject: [time-nuts] Re: Eloran long test from now to August or September.

On 15/09/2023 14:43, john.haine--- via time-nuts wrote:

Yes, I can confirm reception in Edinburgh using a Youloop antenna in an
attached garage.

So, is there any sort of software decoder for the signal?  I don't have a
specialised hardware receiver, just the usual SDR boxes including an Airspy
HF+ Discovery.

Thanks,
David

SatSignal Software - Quality software for you
Web: https://www.satsignal.eu
Email: david-taylor@blueyonder.co.uk
Twitter: @gm8arv

time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an
email to time-nuts-leave@lists.febo.com

Hej Bob,

On Sunday, 24 September 2023 18:38:34 CEST Bob Camp via time-nuts wrote:

Not that I have any experience in (E)Loran, but what about generating a time
signal yourself and adding it to the RF input (in the most basic realization
by simply pulsing off or AM modulating the RF input with an RF-switch, or
slightly more sophisticated by adding a micro-controller generated PRN-time-
code)? Then you you could recover the time-stamp from your recorded, de-
modulated data.

Cheers,
Jürgen