[time-nuts] time/sampling behavior of RTL-SDR

jimlux jimlux at earthlink.net
Wed Mar 8 21:38:49 EST 2017


On 3/8/17 1:14 PM, Michael Wouters wrote:
> The Allan deviation is not frequency stability - it's the ADEV of the noise
> on the receiver signal.

In that article, I think the idea was that they fed a very stable tone 
in, and so they're essentially measuring the ADEV of the LO.

He unfortunately didn't say what the signal he was feeding in was, 
though.  Or was he just integrating the white noise out of the box?

Well, I should get some of these tonight, and if all goes well, and 
there's no panic at work, maybe I can hook one up and look at the 100 
MHz maser signal downstairs.


>
> Cheers
> Michael
>
> On Thu, 9 Mar 2017 at 3:00 am, jimlux <jimlux at earthlink.net> wrote:
>
>> On 3/7/17 9:29 PM, jimlux wrote:
>>
>>>> Sent from my smartphone.
>>>> -------- Original message --------From: jimlux <jimlux at earthlink.net>
>>>> Date: 07/03/2017  22:08  (GMT+01:00) To: Discussion of precise time
>>>> and frequency measurement <time-nuts at febo.com> Subject: [time-nuts]
>>>> time/sampling behavior of RTL-SDR
>>>> Has anyone ever looked at the timing consistency/behavior of the cheap
>>>> RTL-SDR dongles?
>>>>
>>>> That is, if you feed a sine wave in and get the samples out via the USB
>>>> interface, are there missing samples?  What's the ADC clock look like?
>>>>
>>>> If you had two of them, and you determine the relative phase of them at
>>>> some time t0, and you let it run for minutes, how far will it have
>> moved?
>>>
>>
>>
>> Aha, someone has measured the Allan Deviation (although they don't say how)
>>
>> http://www.rtl-sdr.com/wp-content/uploads/2015/03/rtl_R820T2.pdf
>>
>>
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