[time-nuts] Re: Eloran long test from now to August or September.
Jim Lux
jim at luxfamily.com
Sun Sep 24 19:10:11 UTC 2023
I agree. Â Most inexpensive SDRs, and more particularly, the gnuradio or other software, tends not to be designed for deterministic timing. Â 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.Â
Typically, what youâd 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. Â 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. Â Itâs everything after the interface to the host processor thatâs non deterministic. Â
Now, if youâre implementing the SDR on a dedicated processor, with no OS, and careful use of interrupts, you can do it. Â But thatâs what commercial timing receivers do.Â
On Sun, 24 Sep 2023 12:38:34 -0400, Bob Camp via time-nuts <time-nuts at lists.febo.com> wrote:
Hi
The issue with doing this with a low cost SDR board is not so much receiving / demodulating the
signal. Itâs a pretty good bet somebody out there has been there / done that. The issue is pulling
an accurate âtime pulseâ out of your typical SDR setup. This is a somewhat unusual thing to want
to do. Finding a âstockâ setup on a low cost board that does this will be a bit of a challenge.
Bob
> On Sep 24, 2023, at 11:47 AM, paul swed via time-nuts wrote:
>
> 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 11:04â¯AM David Taylor via time-nuts <
> time-nuts at lists.febo.com> wrote:
>
>> On 15/09/2023 14:43, john.haine--- via time-nuts wrote:
>>> This discussion reminds me, there is one eLoran station operating in the
>> UK,
>>> co-located with the MSF transmitter at Anthorn, for research purposes.
>> There is
>>> also some discussion about licensing some new operators mainly for
>> timing
>>> purposes. Does anyone have any information on the coverage available
>> from
>>> Anthorn please? John.
>>
>> 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 at blueyonder.co.uk
>> Twitter: @gm8arv
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