[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.)

These are my opinions.  I hate spam.

More information about the time-nuts mailing list