Re: [Discuss-gnuradio] WBX CW transmit problem

[dvader9]

I have seen the same issue in the last couple of days.

My setup:
Ubuntu 10.04 laptop
UHD + GNUradio 3.3
USRP2 with WBX

TX parameters:
15dB gain, 1090MHz center frequency
4MS/s transmission

RX parameters:
25dB gain, 1090MHz center frequency
4MS/s acquisition

transmitted signal:
U(t) = 10mV + 5mV * sin(2*pi*f*t)
f = 100 kHz

I observe unexpected sinusoidal oscillations in the amplitude at about
400kHz
Oscillation amplitude is on the order of 1mV.

Dave


Aleš Povalač wrote:
> 
> Dear all,
> 
> I have been testing USRP2 with WBX board (#957). Using GNU Radio, I
> have created a simple CW TX system. The problem: output signal is
> oscillating when I set the TX frequencies to 900MHz band. Signal
> output (in time domain) at TX/RX connector from the FSL analyzer is in
> the attachment.
> 
> Settings:
> 868 MHz, 200 kSps, gain 15 dB
> 
> Same results with:
> ./tx_waveforms --rate 250000 --freq 868000000 --gain 15
> 
> The oscillation with ca. 1dB amplitude is present for almost all gain
> settings except the lowest values. I have observed the problem at
> several frequencies from 700M to 1G, sometimes with amplitude over
> 2dB.
> 
> Any ideas about the cause of this problem? Some PA instability or AGC
> loop issue?
> 
> Thanks,
> Ales
> 
>  
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> 
> 

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