[time-nuts] FA2 notes

[Jerry Hancock]

I noticed you can change the baud rate to for instance, 115200, but I can’t get it to stay persistent after power off.  You send it a command of $B11520* to change it to 115,200, but since it only sends like once every 300msecs, it doesn’t really matter the baud.

I found the unit isn’t competitive with the TICC2 and TADD combo.  When measuring a 1PPS signal, the returned values are (around 1.000 000 000) 1.000 000 005 and 0.999 999 995.  Note the ‘5’ as the last digit.  When measuring signals greater than a certain frequency that escapes me, the last digit will then add more resolution switching from units of 5 to 1.

Also, in the doc they talk about digits returned from 8 - 12.  I’ve never seen anything come back from it other than 10:9 or 10.9 format depending on your coding skills.  I tried putting it into ‘High precision” mode by sending it a $E3434* command.

You can change the gate on the fly using the $G* command.  It cycles through the gate times opposed to being able to set it directly.  There are a number of persistent commands that enable default startups, etc.

And one other issue, though it has a somewhat high input level, I noticed I had to put an attenuator on it for measuring the 1PPS out of an HP 5061B Cs.  Otherwise it returned a time of 3hz instead of 1hz for some reason.  All done in 50 ohm mode. 

Otherwise a nice unit for the money.  I’m thinking someone should start a group to move this off list.

Regards,

Jerry


> On Oct 3, 2019, at 8:59 PM, Mark Sims <holrum at hotmail.com> wrote:
> 
> I did a test of the FA2 internal OCXO warm up time.  I powered mine down for 4 fours and then powered it up and measured the frequency as it warmed up.  It looks like it takes 45 minutes to stabilize.  
> 
> Note that it took a week of constant power for the oscillator drift rate to settle down.  The drift on mine seems to be around 0.00025 Hz/day.  I need to do a longer test to better weed out temperature sensitivity.
> 
> BG7TBL internal oscillator warm up time:
> 
> Minutes   Freq error
> 0         221 Hz
> 1         17 HZ
> 2         0.2760 Hz
> 3         0.0500 Hz
> 4         0.0350 Hz
> 5         0.0240 Hz
> 10        0.0130 Hz
> 15        0.0080 Hz
> 20        0.0060 Hz
> 25        0.0050 Hz
> 30        0.0042 Hz
> 35        0.0040 Hz
> 40        0.0034 Hz
> 45        0.0021 Hz <--- stable
> 50        0.0025 Hz
> 55        0.0022 Hz
> 60        0.0020 Hz
> 
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