XG3 synthesizer question

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XG3 synthesizer question

Todd Doucet
The schematic on page 25 of the XG3 manual shows that U1 is a CS2100,
which I assume is a Cirrus Logic CS2100-CP (the one with I2C).   The
datasheet says (as I understand it) that the output frequency from the
chip is 6 to 75 MHz (pin 3).

The Elecraft specs say the unit outputs 1.5 MHz to 200 MHz (with
harmonics also usable up to 1.4 GHz).

So I'm trying to square the CS2100 datasheet with the manual, at least
as I understand them both.


  1. How does the XG3 operate below 6 MHz?

  2. How does the XG3 operate above 75 MHz?

And even more specifically:

  3.  If the XG3 is set to 144 MHz, is the resulting square wave 144
MHz, or a subharmonic?

I'd also be very curious to know if anybody's measured the phase noise
at different distances from the carrier.  The manual indicates -105
dBc/Hz, but doesn't say how far this is from the carrier.  A plot
would be very interesting.

Todd, AE3K
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