As does the Quartzlock A7-MX.
Using the CD4046 (or HC4046) as the phase locked oscillator would
probably be counterproductive as its phase noise is very high (its in
effect an RC oscillator with an effective Q of around1/4)
Bruce
Paramithiotti, Luciano Paolo S wrote:
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: [email protected] [mailto:[email protected]] 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.
Constructive criticism? Comments? Improvements?
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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