[time-nuts] What is the best way to multiply a 10 Mhz

Rick Karlquist richard at karlquist.com
Tue Dec 21 20:09:24 UTC 2010


Burt I. Weiner wrote:
> It would seem the most jitter free way to do it would be to simply
> multiply it up like we used to do.  Some reasonably Hi-Q LC circuits
> could make a nice flywheel and filter out other signals at the same
> time.  Once you have it to the desired signal frequency you could
> condition it to clock your DDS.

Some experience here.  At Zeta Labs, we made a lot of money
building such multipliers.  It is surprisingly hard to do it
correctly and get low phase noise.  At HP, the X6 multiplier
to 60 MHz in the 5065 and the X9 multipler in the 5060/1 were
full employment plans for production engineers, especially if
they were operating under the Peter Principle.  HP definitely
knew less than Zeta about these things.  The two examples of
doing it right at HP were the 8662A and 5071A which had doubler
chains.  I never heard a peep from the production engineers
about the 5071A doubler chain that I designed.  It just worked.  Period.

The doubling was accomplished by wiring the LO and RF ports
of an ASK-1 mixer in series and driving it with a very well filtered
low distortion sine wave (important) at about 10 mW.  The
output filtering was just a ladder of parallel resonant tanks
in shunt and series resonant tanks in series.  The Q of the tanks
was fairly low.  I used a fair number of them to get enough
filtering.  Not a few high Q tanks as you typically see.  There
were no (zero) adjustments.

Rick Karlquist N6RK





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