# [time-nuts] Comparing 10 MHz Oscillators at 10 GHz- an alternative method?

Paramithiotti, Luciano Paolo S luciano.paramithiotti at hp.com
Tue Jan 11 09:49:55 UTC 2011

You can see the Tracor frequency error meter, use the same mixer method you describe but using 9 and 10 MHz frequency to mix toghetherand a decade mfrequency multiplier. The limit of the system is the phase noise of the system and sources. The Tracor use an optional Xtal filter to limit the noise.The filter can be inserted for high multiplication rate or for noisy oscillators.
See tracor schematic http://www.ko4bb.com/Manuals/09)_Misc_Test_Equipment/Tracor_527E.pdf

Luciano

Luciano P. S. Paramithiotti

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of Bruce Griffiths
Sent: martedì 11 gennaio 2011 4.10
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Comparing 10 MHz Oscillators at 10 GHz- an alternative method?

Perry Sandeen wrote:
> List,
>
> While comparing oscillators at 10 GHz might work for some it is indeed a daunting challenge at the very least.
>
> I would like to propose what may be cheaper and more readily achieved
> method for Comparing 10 MHz Oscillators by more of us time-nuts.
> (This is still theoretical)
>
> What I propose is this:
>
> Make two separate, but exactly the same, circuits, one for the reference and the other for the unknown to be measured. They would be located parallel to each on a circuit board.
>
> The input would be divided by a decade counter giving us a 1 MHz signal.  Then we use this signal to phase lock the oscillator section of a CD 4046 to 10MHz.  The 10 MHz signal goes into one port of a LM 1496 double balanced mixer.  The other input would be from a reasonably stable 9 MHz oscillator.  Taking the DBM output into a simple low pass filter we use that 1MHz signal to phase lock the next CD 4046 oscillator to 10 MHz.  Then we start the whole process again.
>
> At any point we chose along the chain or at the end we feed both 10 Mhz signals into a single CD 4046 or similar phase detector and obtain our offset.
>
> Since each set of circuits is fed with the same 9 MHz subtraction oscillator, any deviation of its performance is cancelled.
>
> The required chips are inexpensive and these frequencies are far more manageable than microwaves.
>
>
> Regards,
>
> Perrier
>
>
Eliminate the PLL's as they are not necessary.

However the exercise is probably pointless as the frequency difference between the 2 signals as seen at the output of the cascaded divide and mix chains are reduced by this scheme.
You need to multiply the input signals to a nominal 100MHz then subtract 90MHz using a mixer and repeat the process.

Bruce

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