[time-nuts] Arrays, SDRs and good clocks Re: time-nuts Digest, Vol 168, Issue 21 SDRs and precision time

[jimlux]

On 7/23/18 5:56 PM, Tim Shoppa wrote:
> I thought the thinned array curse was specifically referring to
> transmitting coherent arrays?
> 
> In terms of synthetic aperture receiving arrays, I'm not sure the absolute
> timestamping accuracy you can extract from say, the on-off encoded minute
> marker on the 60kHz reference signal will be good for much of any synthetic
> array used at HF or above. I'm guessing their transmit antenna has a Q of
> 100 or so, meaning that the on-off encoding will have a rise or fall time
> in the millisecond ballpark.
> 
> Wikpedia tells me NPL used to have a "fast code" 100 bit per second signal
> which would imply that their antenna Q is not more than 1000.


Why not use GPS to get your sync?
Using some sort of VLF, LF or HF signal seems subject to propagation 
uncertainty which would be greater than the few ns you could get with 
disciplining a decent oscillator with GPS.

In practice, what you probably want to do is have a pilot tone you can 
distribute across your array.




> 
> Tim N3QE
> 
> On Mon, Jul 23, 2018 at 3:41 PM, Andre <Andre at lanoe.net> wrote:
> 
>> Hi, has anyone ever combined an SDR and Anthorn atomic clock receiver
>> module so that they can be synchronized?
>> the idea here is as a variant of a thinned array similar to WebSDR but
>> using lots of smaller units to get around the thinned aray curse (tm)
>> and combining signals with suitable offset delays so that signal increases
>> at the expense of noise.
>>
>> -Andre
>>
>>
>> ________________________________________
>> From: time-nuts <time-nuts-bounces at lists.febo.com> on behalf of
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>> Sent: 23 July 2018 17:00
>> To: time-nuts at lists.febo.com
>> Subject: time-nuts Digest, Vol 168, Issue 21
>>
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