Navsync doesn't really call it a synthesizer, they call it a Numerically
Controlled Oscillator (NCO). My tests suggest that they're doing what
others have done on the 1 PPS output - change the state of the 10 MHz
output (high to low or vice versa) on a transition of their internal 120
MHz clock. This means that you occasionally get a pulse that's ~8 ns
shorter or (presumably) longer than normal. My unit puts out a short
pulse about 200 times per second. Navsync has an app note where they
say that for some applications a phase-locked cleanup oscillator will be
required.
Ed
Richard W. Solomon wrote:
Dumb question time:
If the NavSync has an on-board synthesizer locked to GPS, why do
you need to lock that to another oscillator ??
73, Dick, W1KSZ
-----Original Message-----
From: gonzo moto <[email protected]>
Sent: Aug 7, 2009 1:32 AM
To: [email protected]
Subject: [time-nuts] PLL question
Hi Guys,
I'm in the process of building a GPSDO which started out life based on G3RUH's
design, but suffered a bit of feature creep.
The GPS I'm using is the NavSync CW12, so I'll run the Freq_Out at 10MHz.
I'm wondering if I should run the PLL at 10MHz or if there is an advantage
dividing the two signals down to (say)10KHz.
Does the averaging at 10kHz (and introduced errors of the dividers) outweigh
the 'no averaging' and no additional errors syncing at the fundamental freq?
I can think of arguments each way, but lack the test equipment to prove either
way.
Suggestions would be appreciated.
Regards,
ian
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