[time-nuts] 35601A as stand-in for 11848A ?

SAIDJACK at aol.com SAIDJACK at aol.com
Sun Jan 6 22:44:30 EST 2008



In a message dated 1/6/2008 14:54:17 Pacific Standard Time,  
bruce.griffiths at xtra.co.nz writes:


>Another issue to consider is mixer dc offset and mixer induced  phase shift.
>Both of these effects will cause the PLL to lock with the  RF and LO
>signals not in exact phase quadrature (unless the correct dc  offset is
>used at the PLL input amplifier).
Hi Bruce,
 
I am pretty sure the Mixers' DC output is near zero when I am in lock,  since 
it only needs to compensate for the Opamps' offset voltage (very  small).
 
While the PLL is working on lock, the Mixer is slowly "homing-in"  on the 
lock voltage, and I don't really see that affecting the noise floor at  all (the 
PLL loop bandwidth is about 1/2Hz, and thus below the analyzers' cut  off, so 
I am actually seeing measurements before the PLL is fully locked  already).
 
Something else is a bit awry here...
 
bye,
Said
 
 
 
 



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