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List: gnuradio-discuss
Subject: Re: [Discuss-gnuradio] dual coherent channel rtl_sdr
From: Heath Hunnicutt <heath.hunnicutt () gmail ! com>
Date: 2013-09-26 22:56:25
Message-ID: CAHW-7WFamiREqSB+s7GvsF4LEPBBft9WcTCGVGymy5Oo4yeS=w () mail ! gmail ! com
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I wonder, since you are emulating the crystal output, if the R820T would
ordinarily drive the crystal to rail-to-rail, square wave output. It might
be worthwhile using a high impedence probe to see what the signal you are
replacing looks like.
I say this because the elonics patent suggests that staying in the linear
region of the amplifiers in the feedback circuit (not rail to rail) reduces
jitter.
On Thu, Sep 26, 2013 at 3:41 PM, Marcus D. Leech <mleech@ripnet.com> wrote:
> On 09/26/2013 06:32 PM, Heath Hunnicutt wrote:
>
> > Juha,
> >
> > Ordinarily, I would choose to feed a clock into xtal_in, this seems
> > logical.
> > However check out the Elonics patent:
> >
> > http://www.uspto.gov/web/**patents/patog/week49/OG/html/**
> > 1385-1/US08324978-20121204.**html<http://www.uspto.gov/web/patents/patog/week49/OG/html/1385-1/US08324978-20121204.html>
> >
> > The main thing to note is that square-wave clock input should be fed to
> > xtal_in for the elonics chip.
> >
> > If you read that patent, it may give you some ideas about feeding a clock
> > to
> > xtal_in of other chips. Maybe other chips will also expect a sawtooth in
> > the linear region of voltage swing, not rail-to-rail square wave. Note
> > the
> > comments in that patent on jitter at square wave, etc.,
> >
> > Nobody on this thread has stated whether they are using e4000 or r820.
> > That
> > would probably be helpful.
> >
> >
> >
> >
> > --
> > View this message in context: http://gnuradio.4.n7.nabble.**
> > com/dual-coherent-channel-rtl-**sdr-tp43784p43851.html<http://gnuradio.4.n7.nabble.com/dual-coherent-channel-rtl-sdr-tp43784p43851.html>
> > Sent from the GnuRadio mailing list archive at Nabble.com.
> >
> > ______________________________**_________________
> > Discuss-gnuradio mailing list
> > Discuss-gnuradio@gnu.org
> > https://lists.gnu.org/mailman/**listinfo/discuss-gnuradio<https://lists.gnu.org/mailman/listinfo/discuss-gnuradio>
> >
> > Well, my tests have been with R820T, which has a clock output that goes
> to the RTL2832U chip.
>
> I've actually tried both sides of Xtal_I and Xtal_O on the R820T, and it
> makes no difference.
>
>
> --
> Marcus Leech
> Principal Investigator
> Shirleys Bay Radio Astronomy Consortium
> http://www.sbrac.org
>
>
>
> ______________________________**_________________
> Discuss-gnuradio mailing list
> Discuss-gnuradio@gnu.org
> https://lists.gnu.org/mailman/**listinfo/discuss-gnuradio<https://lists.gnu.org/mailman/listinfo/discuss-gnuradio>
>
[Attachment #3 (text/html)]
<div dir="ltr">I wonder, since you are emulating the crystal output, if the R820T \
would ordinarily drive the crystal to rail-to-rail, square wave output. It might be \
worthwhile using a high impedence probe to see what the signal you are replacing \
looks like.<br> <br>I say this because the elonics patent suggests that staying in \
the linear region of the amplifiers in the feedback circuit (not rail to rail) \
reduces jitter.<br><br></div><div class="gmail_extra"><br><br><div \
class="gmail_quote"> On Thu, Sep 26, 2013 at 3:41 PM, Marcus D. Leech <span \
dir="ltr"><<a href="mailto:mleech@ripnet.com" \
target="_blank">mleech@ripnet.com</a>></span> wrote:<br><blockquote \
class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc \
solid;padding-left:1ex"> <div class="HOEnZb"><div class="h5">On 09/26/2013 06:32 PM, \
Heath Hunnicutt wrote:<br> <blockquote class="gmail_quote" style="margin:0 0 0 \
.8ex;border-left:1px #ccc solid;padding-left:1ex"> Juha,<br>
<br>
Ordinarily, I would choose to feed a clock into xtal_in, this seems logical.<br>
However check out the Elonics patent:<br>
<br>
<a href="http://www.uspto.gov/web/patents/patog/week49/OG/html/1385-1/US08324978-20121204.html" \
target="_blank">http://www.uspto.gov/web/<u></u>patents/patog/week49/OG/html/<u></u>1385-1/US08324978-20121204.<u></u>html</a><br>
<br>
The main thing to note is that square-wave clock input should be fed to<br>
xtal_in for the elonics chip.<br>
<br>
If you read that patent, it may give you some ideas about feeding a clock to<br>
xtal_in of other chips. Maybe other chips will also expect a sawtooth in<br>
the linear region of voltage swing, not rail-to-rail square wave. Note the<br>
comments in that patent on jitter at square wave, etc.,<br>
<br>
Nobody on this thread has stated whether they are using e4000 or r820. That<br>
would probably be helpful.<br>
<br>
<br>
<br>
<br>
--<br>
View this message in context: <a \
href="http://gnuradio.4.n7.nabble.com/dual-coherent-channel-rtl-sdr-tp43784p43851.html" \
target="_blank">http://gnuradio.4.n7.nabble.<u></u>com/dual-coherent-channel-rtl-<u></u>sdr-tp43784p43851.html</a><br>
Sent from the GnuRadio mailing list archive at Nabble.com.<br>
<br>
______________________________<u></u>_________________<br>
Discuss-gnuradio mailing list<br>
<a href="mailto:Discuss-gnuradio@gnu.org" \
target="_blank">Discuss-gnuradio@gnu.org</a><br> <a \
href="https://lists.gnu.org/mailman/listinfo/discuss-gnuradio" \
target="_blank">https://lists.gnu.org/mailman/<u></u>listinfo/discuss-gnuradio</a><br>
<br>
</blockquote></div></div>
Well, my tests have been with R820T, which has a clock output that goes to the \
RTL2832U chip.<br> <br>
I've actually tried both sides of Xtal_I and Xtal_O on the R820T, and it makes no \
difference.<span class="HOEnZb"><font color="#888888"><br> <br>
<br>
-- <br>
Marcus Leech<br>
Principal Investigator<br>
Shirleys Bay Radio Astronomy Consortium<br>
<a href="http://www.sbrac.org" \
target="_blank">http://www.sbrac.org</a></font></span><div class="HOEnZb"><div \
class="h5"><br> <br>
<br>
______________________________<u></u>_________________<br>
Discuss-gnuradio mailing list<br>
<a href="mailto:Discuss-gnuradio@gnu.org" \
target="_blank">Discuss-gnuradio@gnu.org</a><br> <a \
href="https://lists.gnu.org/mailman/listinfo/discuss-gnuradio" \
target="_blank">https://lists.gnu.org/mailman/<u></u>listinfo/discuss-gnuradio</a><br>
</div></div></blockquote></div><br></div>
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