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

[jimlux]

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  wrote:


On 3/7/17 9:29 PM, jimlux wrote:


Sent from my smartphone.
 Original message From: jimlux 
Date: 07/03/2017  22:08  (GMT+01:00) To: Discussion of precise time
and frequency measurement  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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[time-nuts] Install a 5061A/B tube into a 5071A!

[cdelect]

Well I thought that would get your attention!
It's not quite as simple as that, however it CAN be done.
First you need a good "mini" tube scavenged out of a 5061A/B.
These smaller diameter tubes HP made for 5061A/B replacements
are essentially a 5071A tube with different connectors.
Then you need an EEPROM removed from a dead 5071A tube that
has a thermistor value close to the "mini" tube.
Tom Van Baak has the paper on his site, you can read about the results.\
 I got installing "mini" tubes into several 5071A units.
http://leapsecond.com/corby/HP-5071A-with-5061A-4.docx
Also included are the results of using a standard tubes EEPROM
on a high performance tube and visa versa to extend the tubes life!
Now that I'm done with the experimenting I have two 5071A with
good "mini" tubes installed and several good "mini" tubes for sale.
Buyers of the 5071A can buy a "spare" tube at a discount.
Both 5071A are missing the front door cover and the two perforated
side panels.
Please contact me off list for details, pictures and plots.

Cheers,

Corby Dawson

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

[jimlux]

On 3/7/17 9:29 PM, jimlux wrote:


Sent from my smartphone.
 Original message From: jimlux 
Date: 07/03/2017  22:08  (GMT+01:00) To: Discussion of precise time
and frequency measurement  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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