[time-nuts] is there a cheap and simple way to measure OCXOs?

Bob Camp lists at rtty.us
Fri Jun 1 22:26:35 UTC 2012


Hi

The TI ADS1271/4/8 might make a nice alternative to a sound card. They have a bit better DC performance than a lot of the sound card chip sets. There's an EVM available for them, but I haven't really looked much at it. The nice thing is that you could get 4/8 channels of simultaneous samples. Nice for doing three (or 4 or 8) corner hat sort of stuff.

Bob

On Jun 1, 2012, at 5:02 PM, Bruce Griffiths wrote:

> The AP192 exhibits an input noise floor of around 100nv/rtHz ( for a low impedance source) or so (IFIRC - when I measured it.) so with an HP 10534A/B or 10514A/B a post mixer amplifier gain of 60db or so is required to ensure that mixer/phase detector noise dominates. The equivalent input noise tends to be somewhat higher in the vicinity of 10Hz.
> 
> Other high performance sound cards should have similar input noise.
> 
> Bruce
> 
> shalimr9 at gmail.com wrote:
>> If you can offset one enough to have the output from the dbm in the audio band, you could use a sound card based spectrum analyzer to evaluate phase noise. Some sound cards may work down to 10 Hz, but their performance there is usually not specified. Bruce Griffiths has information on some high performance audio cards and maybe he can chime here.
>> 
>> Using the 3 corner hat method, you could identify the relative phase noise performance of three oscillators.
>> 
>> It will not help with longer term variations though.
>> 
>> Didier KO4BB
>> 
>> Sent from my BlackBerry Wireless thingy while I do other things...
>> 
>> -----Original Message-----
>> From: Attila Kinali<attila at kinali.ch>
>> Sender: time-nuts-bounces at febo.com
>> Date: Wed, 30 May 2012 16:59:39
>> To: Discussion of precise time and frequency measurement<time-nuts at febo.com>
>> Reply-To: Discussion of precise time and frequency measurement
>> 	<time-nuts at febo.com>
>> Subject: Re: [time-nuts] is there a cheap and simple way to measure OCXOs?
>> 
>> On Wed, 30 May 2012 07:18:12 -0700
>> Jim Lux<jimlux at earthlink.net>  wrote:
>> 
>>   
>>> Got a mixer around, so you can beat them against each other (or against
>>> your 5680)?
>>>     
>> Not yet. I'm currently thinking about geting an mixer from minicircuits
>> for the ZX05-1L[1] and a low pass filter BLP-1.9[2].
>> 
>> But what then? The frequency offset is low enough that it is still
>> problematic to measure with standard measurements instruments.
>> And the phase noise.. out of question.
>> 
>> 			Attila Kinali
>> 
>> 
>> 
>> [1] http://217.34.103.131/pdfs/ZX05-1L+.pdf
>> [2] http://217.34.103.131/pdfs/BLP-1.9+.pdf
>>   
> 
> 
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