[time-nuts] time-nuts Digest, Vol 101, Issue 152
Hal Murray
hmurray at megapathdsl.net
Mon Dec 31 08:55:42 UTC 2012
jimlux at earthlink.net said:
> When designing the system to do coherent two way ranging to the Juno
> spacecraft orbiting Jupiter, we found that the rotating magnetic field
> (because the spacecraft spins at 2RPM in Jupiter's magnetic field) was
> enough to modulate the circuits that track the received signal and generate
> the transmitted signal ( basically a PLL)...
How strong is the magnetic field near Jupiter? I assume big, but maybe the
orbiters don't get that close.
How did you test it? I'd guess a big chamber with big Helmholtz coils.
---------
I just took a fridge magnet to my box of (somewhat?) good oscillators. The 2
big ones had steel cases. The smaller Vectron had a steel base but
non-magnetic top.
----------
jimlux at earthlink.net said:
> A bigger concern might be if you're locking something you care about to
> that oscillator. The PLL might be more sensitive (particularly things like
> the op amp circuitry driving the VCO... there's probably some sort of
> physical loop in the wiring between the inverting and noninverting inputs
> of the op amp.
Does that mean we should put that stuff into a steel box? (With junk like
power supplies outside.)
--
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