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Re: [Discuss-gnuradio] questions about USRP2 sink block and upconversion
From: |
Markus Heller M.A. (relix GmbH) |
Subject: |
Re: [Discuss-gnuradio] questions about USRP2 sink block and upconversion |
Date: |
Thu, 04 Nov 2010 04:11:26 +0100 |
Hi Marcus,
great, now I know what was wrong. I didn't expect my dummy load to be so
safe. It was a real signal lock :-)
For all the others, here's a short experiment report:
Here are the parameters:
* Sample rate 200k
* Signal source at 1 KHz, amplitude at a minimum of 0.001 - to
make sure that a bad SWR does no harm. BTW, this is a good
counter check that you can really influence the output power!
* USRP2 sink: interpolation 500, frequency 14 MHz
Result: I hear a clear signal at 14.000 MHz, +/- 1 kHz
Thanks very much!
BR & 73s
Markus
DL8RDS
Am Mittwoch, den 03.11.2010, 22:46 -0400 schrieb Marcus D. Leech:
> On 11/03/2010 06:57 PM, Markus Heller M.A. (relix GmbH) wrote:
> > I kindof have a similar problem. Guess I havent understood this yet.
> >
> > I want to generate a very basic signal at 10.000000 MHz. A little up or
> > down is not relevant, but I want to hear a signal at all. I have a very
> > sensitive HF receiver right next to my dummy load, so that should work
> > with a very faint rest.
> >
> > In GRC I have a signal generator and a USRP2 sink.
> >
> > Can you please tell me reference values for
> > * sample rate
> > * interpolation on the usrp2
> >
> The maximum interpolation rate on the USRP2 is 512, which means that the
> narrowest baseband
> signal you can squirt over the Ethernet to it is 100Msps/512, or
> 195312.5Hz.
>
> So, the sample rate for your (complex) signal should be at a minimum,
> 195312.5Hz, and then
> request an interpolation rate of 512 when setting up the USRP2 sink.
>
> Although, it may be "tidier" to use an interpolation of 500, and thus a
> sample rate of 200KHz.
>
> Create a 1Khz sinusoidal signal, sampled at 200KHz, send that to your
> USRP2, tuned to
> 10.0000MHz. You should see that on your HF receiver in CW mode,
> somewhere around
> 10.001MHz or so (+/- handwaving).
>
> The interpolation tells the FPGA in the USRP2 how to "expand" the
> bandwidth of your signal to
> match the fixed sample rate of the DAC that feeds the analog Tx chain.
>
> The sample rate of your signal source had better match what you told the
> USRP2 for interpolation,
> or your signal won't be interpreted correctly.
>
> Different types of signals have different inherent bandwidths, and you
> chose sample rates and
> interpolation rates to "fit" the signal at hand. A typical amateur
> radio SSB signal, for example,
> is only a couple of Khz wide, but remember that the *minimum*
> bandwidth you can squirt over
> the Ethernet, and get interpolated up to the DAC rate is 100Msps/512.
> Which means that
> narrow-band signals tend to get oversampled by quite a bit inside the
> flow-graph before
> they end up being presented to the USRP2.
>
>
>
Re: [Discuss-gnuradio] questions about USRP2 sink block and upconversion, alexander levedahl, 2010/11/03
Re: [Discuss-gnuradio] questions about USRP2 sink block and upconversion, Steve Mcmahon, 2010/11/04