[time-nuts] Inexpensive Alternative to a 5120A

Bob Camp kb8tq at n1k.org
Mon Oct 10 08:17:35 EDT 2016


> On Oct 10, 2016, at 7:06 AM, Chris Albertson <albertson.chris at gmail.com> wrote:
> Let's back up, start over.   I want to use an SDR-like thing to
> characterize my new 10MHz oscillator, or actually to compare it to my
> Thunderbolt
> What are the steps?

The test document on an OCXO or a GPSDO runs into several dozen to several 
hundred pages. It also sub-references multiple documents of similar size. All that 
gets only just so deep. The assumption is that routine maintenance and calibration
have taken care of a lot of other things. You do *not* want to dig into all that :)

> Then after we list the steps I want to see why so many samples are required

The original paper did a direct sample of the signal. Nyquist gets you into the > 20 mega
sample range. 

> Or maybe a better way to ask is "How will the results be limited if I
> can only sample at 2.3 MSPS?

They use the dual ADC simultaneous sample process to reduce the jitter of the
sample. It’s in the paper. 

> Obviously I'n not directly sampling there 10MHz signal.  I'm sampling
> there frequency difference that a mixer gives me.

Then build a DMTD with a stable / low noise reference rather than the poor
stability reference in a SDR dongle. 

Again, no free lunch :)


> On Sun, Oct 9, 2016 at 4:16 PM, Bob Camp <kb8tq at n1k.org> wrote:
>> Hi
>>> On Oct 9, 2016, at 6:18 PM, Chris Albertson <albertson.chris at gmail.com> wrote:
>>> Likely the lowest cost way to get into that is with a TV tuner USB
>>> dongle. They cost about $20.   People are able to get about 2.4 mega
>>> samples per second.
>> Except that you need about 30 mega samples ...
> -- 
> Chris Albertson
> Redondo Beach, California
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.

More information about the time-nuts mailing list