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Date: Sun, 10 Apr 2011 17:11:09 +0100
Message-ID: <BANLkTimvS_Mi3P3d2su6eLdgbqunjCQ4Uw@mail.gmail.com>
From: Andy Talbot <andy.g4jnt@gmail.com>
To: rsgb_lf_group@blacksheep.org
DomainKey-Status: good (testing) 
Subject: Re: GPS Sync (was: Re: LF: Wow 8.9696kHzOssi?)
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No, 30 - 90ns is pretty typical of most modern GPS receivers now.

But I'm impressed you can get that good averaging from a sampling rate much
lower than that

Andy
www.g4jnt.com



On 10 April 2011 12:39, wolf_dl4yhf <dl4yhf@freenet.de> wrote:

> Hello Stefan,
>
> Yes, the charm of the GPS-sync'd sampling is that it allows truly coherent
> transmission - even after the program was shortly stopped, PC rebooted,
> generator re-fuelled, or whatever strange things may happen. The sine wave
> generator will (optionally) not calculate the argument based on the number
> of soundcard samples, but derived from the GPS-derived time of day. Which,
> with the GPS 18x LVC mentioned before, seems to have a resolution (not
> neccessarily a precision) in the sub-microsecond range (192 kHz SR -> 5.x
> microsecond samples, but internally interpolated to a higher sample rate
> near the slope of the sync pulse).
>
> At 192 kHz sampling rate, I get a standard deviation in the measured pulse
> position of only 30 to 60 nanoseconds (per one-second-interval) measured
> over one minute, which almost sounds too good to be true. Thus i'm a bit
> sceptic, this needs more testing.
>
> Some preliminary info about the GPS-based calibration is already available
> here:
> http://www.qsl.net/dl4yhf/speclab/frqcalib.htm#gps_pps_output
>
> Note: The NMEA decoder for the soundcard is not implemented in the SL
> version on my website. It will be implemented when the weather(!) permits
> ;-)
>
> 73,  Wolf DL4YHF
> (off for a walk now..)
>
>
>

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<div>No, 30 - 90ns is pretty typical of most modern GPS receivers now.</di=
v>
<div>=A0</div>
<div>But I&#39;m impressed you can get that good averaging from=A0a sampli=
ng rate much lower than that</div>
<div>=A0</div>
<div>Andy</div>
<div><a href=3D"http://www.g4jnt.com/">www.g4jnt.com</a></div>
<div><br><br>=A0</div>
<div class=3D"gmail_quote">On 10 April 2011 12:39, wolf_dl4yhf <span dir=
=3D"ltr">&lt;<a href=3D"mailto:dl4yhf@freenet.de">dl4yhf@freenet.de</a>&gt=
;</span> wrote:<br>
<blockquote style=3D"BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8e=
x; PADDING-LEFT: 1ex" class=3D"gmail_quote">Hello Stefan,<br><br>Yes, the=
 charm of the GPS-sync&#39;d sampling is that it allows truly coherent tra=
nsmission - even after the program was shortly stopped, PC rebooted, gener=
ator re-fuelled, or whatever strange things may happen. The sine wave gene=
rator will (optionally) not calculate the argument based on the number of=
 soundcard samples, but derived from the GPS-derived time of day. Which,=
 with the GPS 18x LVC mentioned before, seems to have a resolution (not ne=
ccessarily a precision) in the sub-microsecond range (192 kHz SR -&gt; 5.x=
 microsecond samples, but internally interpolated to a higher sample rate=
 near the slope of the sync pulse).<br>
<br>At 192 kHz sampling rate, I get a standard deviation in the measured=
 pulse position of only 30 to 60 nanoseconds (per one-second-interval) mea=
sured over one minute, which almost sounds too good to be true. Thus i&#39=
;m a bit sceptic, this needs more testing.<br>
<br>Some preliminary info about the GPS-based calibration is already avail=
able here:<br><a href=3D"http://www.qsl.net/dl4yhf/speclab/frqcalib.htm#gp=
s_pps_output" target=3D"_blank">http://www.qsl.net/dl4yhf/speclab/frqcalib=
.htm#gps_pps_output</a><br>
<br>Note: The NMEA decoder for the soundcard is not implemented in the SL=
 version on my website. It will be implemented when the weather(!) permits=
 ;-)<br><br>73, =A0Wolf DL4YHF<br>(off for a walk now..)<br><br><br></bloc=
kquote>
</div><br>

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