[time-nuts] Fury Realhamradio listing
Peter Schmelcher
nebula at telus.net
Mon Aug 20 05:24:50 EDT 2007
>C) I don't believe the Z3801A has 100ps single shot resolution and accuracy
>(for resolution doesn't do anything without accuracy) until someone will
>prove it to me. And even then it would be wasted resolution since the GPS
>1PPS
>source noise will totally swamp out any benefit a 100ps resolution
>would give.
Hi Said,
I inadvertently measured the TI resolution of a Z3816A and it is a stable
100ps.The setup was a slightly modified VP receiver that has a phase locked
LO (a 3325A locked to the OCXO) which replaced the normal UT GPS receiver
in the Z3816. The measurements were made during a "hanging bridge" when the
GPSDO servo loop is effectively open circuit for phase errors smaller than
the saw tooth. The HP motherboard then averages 5 GPS pps samples so I
guess the servo loop has control resolution of 20ps.
A side effect of the 5 sample average is the opportunity to reduce the
effective saw tooth error to 1/5 when the GPS LO is adjusted about 0.4 Hz
high. This causes the GPS pulse position to advance about 20ns every second
and repeat every 5 seconds creating a more stable average.
Enjoy
Peter
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