Re: LF: Portable VLF/ULF recording system with PPS+NMEA

[Michel Brunel <f5wk@mterrier.net>]

Hallo Stefan,

Looks promising, what sound card are you using and if you can read it, what is the audio codec chip ?  
I recently tried to replace the 12 MHz crystal of a CUA-202, but the onchip PLL of the PCM2902 ruined my effort (too bad a jitter)

For my future Ebnaut operation,  I just set up a "Stratum 1 time box" with a Raspberry PI2 and a tiny GPS receiver (VK16E)
The 1PPS is directly sent to a GPIO and managed by the kernel (Raspbian Jessie) NTPQ reports an accuracy of 2E-19 which
translates to 2 ms 
Ah, Wolf's ntp client works like a charm with the Rpi ntp server !  That's a great internet free solution.

73,

Michel - f5wk



Le mardi 5 juillet 2016 à 16:45:52, DK7FC écrivait :

> Hi all,

> I've completed my portable VLF/ULF(audio) recording system.
> See: 
> https://dl.dropboxusercontent.com/u/19882028/ULF/VLFesULF%20portable%20recording.jpg


> The system consists out of a:
> - Raspberry Pi 2B
> - DC/DC converter with a 5.0V output (80% efficiency)
> - 7 Ah lead acid battery
> - Stereo input soundcard
> - 32 GB USB stick
> - NEO-6M GPS module (including antenna)
> - (shut down button)
> - (switch for starting/stopping a recording)

> The latest add-on, the GPS module now allows to record 1PPS impulses and 
> NMEA data for most accurate and glitch-free(corrected) recordings, 
> absolute timestamps as well as location data.
> The recording is stred as a wav file to the USB stick directly.
> It consumes 160 mA at 12V during a record. With the battery it should be 
> no problem to record for nearly 2 days.
> Future ULF reception tests can now be done with this improved technique...

> 73, Stefan






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