[time-nuts] Trimble Thunderbolt E frequency pulling.

GandalfG8 at aol.com GandalfG8 at aol.com
Mon Nov 23 11:30:48 EST 2015

>   Before I start probing any deeper I'd be interested  to hear if anyone
> else  come across this with the Thunderbolt E.  

Is it thermal?  Can you measure the frequency shift before it has  time to 
warm up?

Switching the impedance at the counter itself resets any plot  that's in 
progress, which does introduce some delay, so I put together a  small switch 
box that could be inserted into the coax and confirmed it's a  rapid effect 
that's unlikely to be thermal.
It's even more observable with disciplining turned off  and there's no 
attempt to correct it, I can toggle back and forth  between the two frequencies 
just by switching the load.
One thing I did get wrong though when transposing my notes, switching  from 
low to high impedance at the 10Mhz output will increase the frequency,  
with high to low decreasing it again, which is the reverse of what I originally 

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