[time-nuts] Sorry wrong title on previous message.
jmiles at pop.net
Tue Oct 4 19:28:06 EDT 2011
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-
> bounces at febo.com] On Behalf Of Paul A. Cianciolo
> Sent: Tuesday, October 04, 2011 3:57 PM
> To: 'Discussion of precise time and frequency measurement'
> Subject: [time-nuts] Sorry wrong title on previous message.
> I have been using your TimeLab for a while now.
> Here is what I do. The 10 MHz ref go into start and the dut 10 MHz goes
> into stop, both terminated in 50 ohms.
> I use the I PPS out of the 3801 to Arm the 5370b, so I assume the sample
> rate to TL is 1 PPS. I am set to "use in coming sample rate"
> What I would like to know is .. Can I use TL to make my phase corrections
> the DUT before commencing a trace?
> at 10 samples per sec I use the" phase original" which is moving fairly
> to try to obtain a flat line across the screen.
> Is this a reasonable way to do this? Is there another way within TL?
I'm not sure what you mean by phase corrections.... aren't you just trying
to observe the oscillator's stability?
Are you asking about how to take the linear residual out of the phase slope?
You can use 'r' to toggle the linear residual display on or off, or you can
actually take the linear slope out of the phase data (aka the frequency
offset) by hitting ctrl-'o'. These have the same effect but 'r' does not
actually modify the data.
Similarly, linear or quadratic frequency drift can be removed with ctrl-'l'
Two things that commonly go wrong with TI measurements: 1) if the
frequencies at the start and stop jack are sufficiently different to cause
multiple wraps per second, then TimeLab cannot unwrap the phase properly and
your data will be invalid. Tune the oscillator closer to 10 MHz in this
case. 2) At 10 pps, especially if using a Prologix adapter, you need to
use the Display Rate control to reduce the rate at which the counter takes
readings. (In the example I sent offline, I used a 10-pps external arming
source, but cranked the display rate down to about the 12:00 position to
limit the readings to about once per second.)
-- john, KE5FX
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