[time-nuts] Homebrew frequency counter, need help

Bob Camp kb8tq at n1k.org
Fri Dec 12 08:18:18 EST 2014


> On Dec 12, 2014, at 4:04 AM, Tom Van Baak <tvb at LeapSecond.com> wrote:
> This large posting is from Li Ang.
> /tvb
> ----- Original Message ----- 
> From: Li Ang 
> To: Discussion of precise time and frequency measurement 
> Sent: Thursday, December 11, 2014 7:37 AM
> Subject: Re: [time-nuts] Homebrew frequency counter, need help
> Hi Bob,
>   I've sent the PCB to the factory and I am waiting for the new board. This time, it's a 4-layer borad and changed from CPLD to FPGA. This is the first time of FPGA & 4-layer project. Hope everthing be OK.

Very nice looking. I hope it works !!!

>   TPS79333 as the LDO for TDC. Better PSRR and noise spec than before (XC6206). Analog and digital parts have their dedicated LDO. 
>   While I'm waiting the the new board. I did a test with PRS10 & FE5650 with current board. It's strange that the 20s adev of "without linear regression" is better than "with linear regression”

Be careful pre-processing ADEV data. There are a variety of statistical “traps” you can fall into. An overly simple explanation is that ADEV looks at noise and that most pre-processing is a filter. Filters take out noise. Finding one that only takes out the “bad noise” and keeps the “good noise” can be quite difficult. 

What exactly are you doing in your linear regression computation? 


> .<bottom_layer.GIF><power_plane.GIF><top_layer.GIF><adev.gif>_______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.

More information about the time-nuts mailing list