[time-nuts] Re: Eloran long test from now to August or September.

[Lester Veenstra]

Agree very old and multi used idea.   
For the clever ones in DSP, penetrate a time coherent spread spectrum that can be inband but under the noise floor of the collection bandwidth.  Correlate on receive in the same sample environment as you are doing science.

Lester B Veenstra  K1YCM  MØYCM  W8YCM   6Y6Y W8YCM/6Y 6Y8LV (Reformed USNSG CTM1)
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-----Original Message-----
From: Jim Lux via time-nuts [mailto:time-nuts at lists.febo.com] 
Sent: Tuesday, September 26, 2023 3:33 PM
To: jeanmichel.friedt at femto-st.fr; time-nuts at lists.febo.com
Cc: Jim Lux
Subject: [time-nuts] Re: Eloran long test from now to August or September.


	


Exactly.. That does work, although it requires opening up your RTL-SDR (and on V3, in HF receiver mode, the RF input is directly coupled to the Q input, without going through the front end downconverter.). It didn’t work well.
And ultimately, I was trying to figure out something that would work at Ku band, so I could “calibrate out” the delay through the LNB, the coax, and the RTL-SDR.  
The basic technique has been around since the 1960s.  Bracewell used it at Stanford, and a similar scheme was used for the Jansky VLA in New Mexico.


On Tue, 26 Sep 2023 19:24:21 +0000, jeanmichel.friedt at femto-st.fr wrote:

> I did it with 4 RTL-SDRs, and I’ll scrounge up the measurements. My first attempt was just to
> couple the 1pps from a GPS module into the inputs - that’s not easily detectable (I was hoping that
> the fast edges would be sufficiently broadband to be detectable in the sampled data stream -
> nope..)

See attached: I capacitively inject the 1-PPS on the RTL2832 input (either I or Q), not
the R820(T2) radiofrequency frontend. This allows for timestamping on the rising edge
of GPS 1-PPS the datastream fetched by the ADCs of the RTL-SDR.

Best, JM



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