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From: =?UTF-8?Q?Wolfgang_B=c3=bcscher?= <dl4yhf@freenet.de>
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Date: Sun, 30 Oct 2016 21:53:48 +0100
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Subject: Re: LF: Re: GPS pulse timing
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Hello Stefan,

857 ns standard deviation in the 1-second pulse timing at 48 kHz sample 
rate isn't spectacularly good, but considering the fact that the pulses 
are sent over a 'lossy' Vorbis-compressed stream, it's not so bad.
You could possibly do better by running Paul's vlfrx tools on the RasPi, 
and resample the data *there* (on the remote site) to exactly 48 kHz 
before sending them over the line. Possibly easier said than done (since 
vttime.c needs a differently shaped sync pulse), so before going that 
way you could check the GPS module by connecting if directly to the PC 
with a high-grade soundcard
(like the E-MU 0202 or similar 'large boxes' where the oscillators are 
less affected by thermal drift than the miniature USB sticks).

Oh well, time to get back to the projected PIC-based, GPS-synced OXCO 
with fast internal ADC and DSP. But the thing has neither WLAN nor 
Ethernet :o( but the hardware is dead cheap and consumes far less power 
than a Raspberry :o)

73,
   Wolf .

Am 30.10.2016 um 21:37 schrieb DK7FC:
> Hi Wolf,
>
> Am 30.10.2016 21:15, schrieb Wolfgang Büscher:
>> Hi Stefan,
>>
>> No significant improvement if the soundcard really supports 96 kHz 
>> sampling or more,
>> and if the standard deviation in the GPS-based pulses is already 
>> below 100 ns.
> OK.
>> That is displayed on the SR panel as 'StdDev60' (standard deviation 
>> in the recent 60 1-second pulses).
> I know :-)
> See the capture attached. This is the VLF stream from the tree. Could 
> it have to do with the vorbis stream? Or is it due to the module? The 
> module receives 7 satellites at the moment?
>
> 73, Stefan