[time-nuts] New NTBW50AA

Bob Camp lists at rtty.us
Mon Sep 9 11:52:53 UTC 2013


Hi

I think you may be looking at the ADEV and reading more into it than you should. 

It's a table of ADEV vs Tau. The longer you have data for, the larger Tau (seconds) it will display. It's not getting better as it displays more data it the table, it's just got more seconds of data. 

ADEV should be a measure of stability. In the case of a GPSDO, you have an OCXO that's locked to the GPS. As the GPS moves, the OCXO follows the GPS. There is no independent "referee" to let you know if things are moving in the right or wrong direction. Put another way, it's like looking at the reference on your counter by plugging it into the front of the counter. Because the OCXO always follows the GPS, the ADEV as shown will always get better with time. You are getting further and further inside the control loop. 

To really know what's going on with the GPSDO you need an independent standard to compare it to. Even a cheap Rb will help you figure out how stable the frequency really is. A Cs or a Hydrogen Maser would (of course) be better. 

Bob

On Sep 8, 2013, at 5:51 PM, quartz55 <quartz55 at hughes.net> wrote:

> I did the &a command and it seems to have straightened out.  I don't know what I did but now it toggles from full screen to a window fine for now.  It changed the el and amu masks. I'll let it run overnight see how it is and then try moving the antenna to what I think may be it's permanent position and see if it works there.  I goggled the Lat Lon and it puts the antenna right on my deck where I have it.  I notice the mouse acts erratically sometimes, I have a laptop I may press into service for this thing but it's a vista OS.
> 
> I found lots of info in heather.cpp, but I wonder if the keyboard commands aren't somewhere easier to find, other than the space bar.
> 
> It's gone up to 3.63e-12 now.
> 
> Dave
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