Re: [Discuss-gnuradio] [USRP-users] USRP N210 Signal Phase Issue

[Jonathan Fox]

It works now, although with some U's on the console, they were there before anyways. I forgot to run systctl -w net.core.rmem_max=50000000 and net.corewmem_max=1048576. As soon as I ran it the harmonics went away.

On Wed, Jan 8, 2014 at 4:26 AM, Ralph A. Schmid, dk5ras <address@hidden> wrote:

May it be just some lost packet or smth. like that? It looks very similar when USB does not catch up when using my USRP1 and BladeRF... Missing samples can create funny signals.

 

Ralph.

 

 

From: discuss-gnuradio-bounces+ralph=address@hidden [mailto:discuss-gnuradio-bounces+ralph=address@hidden] On Behalf Of Matt Ettus
Sent: Wednesday, January 08, 2014 2:25 AM
To: Jonathan Fox
Cc: GNURadio Discussion List
Subject: Re: [Discuss-gnuradio] [USRP-users] USRP N210 Signal Phase Issue

 

 

It could be the usrp digitally clipping, not the analyzer.

 

Matt

 

On Tue, Jan 7, 2014 at 5:17 PM, Jonathan Fox <address@hidden> wrote:

On Tue, Jan 7, 2014 at 7:11 PM, Marcus D. Leech <address@hidden> wrote:

 

Try reducing the amplitude to 0.7.  Another possibility is that your computer can't keep up.  If you are using one of the standard programs, are there U's printing in the terminal?

 

Matt

 

Also, what RF gain are you setting?  Does it exceed the maximum input level of the spectrum analyser?

Are you connected directly, or with an antenna?

 

On Tue, Jan 7, 2014 at 3:03 PM, Jonathan Fox <address@hidden> wrote:

A colleague and I are sending a simple signal in GNU Radio (sine wave, 1 MHz, amplitude of 1) to the USRP sink and have the center frequency at 500 MHz. The N210 USRP is hooked up to an Agilent spectrum analyzer. On the analyzer we are seeing a weird phenomena every two seconds. At first we see the carrier frequency and two sidebands from the sine wave (see attached normal.gif). Then after two seconds we get two bursts of multiple harmonics (see odd.gif).

 

The question is, why is this happening? Does the phase of the 1 KHz signal become discontinuous before or after being sent to the USRP?

 

Thanks,

 

Jon Fox

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Marcus Leech

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Shirleys Bay Radio Astronomy Consortium

http://www.sbrac.org

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I don't recall seeing any U's but I can recheck tomorrow. The gain on the USRP was set to -2. The USRP was connected directly with an SMA cable. The analyzer is an Agilent E4440A, the Analyzer is rated for at least 1 Watt on average, 100 Watt on a peak pulse (with the built-in attenuator in use). While I am not ruling out the maximum input I thought the N210 tops out at 0.5 Watts due to FCC regulations.

 

Thanks

Jon

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