[time-nuts] Choke Rings and Points North

Tom Van Baak tvb at LeapSecond.com
Tue Dec 16 08:59:21 EST 2014

> Clever idea, but..
> Most rotary joints have more phase and amplitude variability than the 
> antenna.
> So you're stuck with rotating back and forth with a cable that's flexing 
> and now you get to measure the phase variability of the coax.

I was thinking of some sort of non-contact RF bridge that would allow either side to rotate independently. Converting to optical would make this easy, but there must be a way to do it at 1.5 GHz too.
> You really need to have your entire GPS system antenna and receiver on 
> the rotating table (which will need to have temperature controls, etc.)
> Oh, what a pit one can descend into with the goal of reducing everything 
> to a minimum error.

In this case the goal is actually not minimizing error. The goal is to vary each possible error source with its own prime modulation period. Collect lots of data and the FFT tells you how much each error contributes to the pie.

For example, instead of temperature control you modulate temperature by 5C over a 13 hour period. Instead of voltage control you modulate the 5V antenna power by 10% every 1.7 hours, etc.


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