To prepare for the implementation of dead zone countermeasures I did
some measuring of the dead zone band width versus frequency of the
subharmonic
The test setup use a generator with two outputs, one fixed at 10MHz and
one variable to test the dead zone. The fixed 10MHz was send to one
input of the timestamping counter. The variable frequency output was
send to the other input.
The reference clock used for the timestamping was set to 200 MHz and,
through its VC-TCXO, locked to the fixed 10MHz using a SW control loop
updating the voltage to the VC-TCXO once every 10 seconds.
As the generator used was only able to set frequency at 0.1 Hz
resolution there where some limitations in this assessment.
The dead zone was observed on the sub harmonics of 200MHz and its
harmonics. The size of the dead zone was very much dependent on the used
frequency
Below 1MHz the width of the dead zone was below 0.1Hz and thus not
observable
At 10 MHz the width was about 1 Hz
At 40 MHz the width was about 2 Hz
At 80 MHz the width was about 10Hz
This makes implementing dead zone counter measures doable as with lower
frequency subharmonics the width of the dead zone decreased thus putting
a limit on the amount of subharmonics to include in the calculations and
this makes it unlikely there is a scenario where the two input
frequencies used make it impossible to find a reference frequency
avoiding the subharmonics.
_______________________________________________
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.
