[time-nuts] Noob question on measuring Allan Deviation on 10 MHz source

Chuck Forsberg WA7KGX N2469R caf at omen.com
Wed Dec 14 16:10:59 EST 2011


Once you get the frequencies matched with a fraction of 1 Hz,
I would measure the phase between the 10 MHz source and the
10 MHz from the Trimble.

On 12/14/2011 12:29 PM, George Dubovsky wrote:
> List;
>
> OK, I need to measure the stability of a 10 MHz sine-wave source. After
> reading a lot of background info on this list and some of the sources that
> were referenced, I thought I could get away with a frequency measurement. I
> now think I was wrong.
>
> What I have is an Agilent 53230A counter (a pretty capable box - claims 20
> ps one-shot resolution in TI mode), a Trimble Thunderbolt, the 10 MHz
> oscillator to be measured,  and a copy of Stable32. My first effort
> involved feeding the Trimble 10 MHz into the counter as its Ext Reference.
> I then fed the Trimble 1pps into the Ext Trigger input of the counter and
> fed the sinewave 10 MHz signal to be measured into Ch 1 of the counter. I
> then captured the frequency reading of the counter every second and stuffed
> those numbers into a file. I collected about 20 hours of frequency
> readings, but when I imported that into Stable32 and attempted to do an
> Allan Dev plot, it didn't look very good - specifically, the sigma numbers
> were in the region of 10e-2 to 10e-4.
>
> So, I grabbed another Thunderbolt and attempted to do the same measurement
> on it, figuring that everyone (but me) has taken data on a T'bolt, so I
> could just look on tvb's site or some such to find proper data on a Tbolt.
> Again, the plot didn't look like it should.
>
> Am I going to have to go to time interval measurements to do what I want?
> And does this mean I will have to square up my 10 MHz signal to have real
> edges?
>
> geo
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-- 
Chuck Forsberg WA7KGX N2469R     caf at omen.com   www.omen.com
Developer of Industrial ZMODEM(Tm) for Embedded Applications
   Omen Technology Inc      "The High Reliability Software"
10255 NW Old Cornelius Pass Portland OR 97231   503-614-0430





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