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Re: [Discuss-gnuradio] ADC calibration


From: Matt Ettus
Subject: Re: [Discuss-gnuradio] ADC calibration
Date: Fri, 13 Aug 2010 12:26:27 -0700
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.11) Gecko/20100720 Fedora/3.0.6-1.fc12 Thunderbird/3.0.6

On 08/13/2010 12:14 PM, Daniel Halperin wrote:
On Tue, 10 Aug 2010, Matt Ettus wrote:

When using a BasicRX or LFRX with the PGA set at 0dB gain (USRP1
only), +10dBm is full scale on the ADC. On the USRP2 full scale on the
ADC is full scale when it gets back into gnu radio. On the USRP1 full
scale on the ADC is (1.67/2) times full scale due to the gain of the
CORDIC.

+10dBm = 2Vpp = 1 Vpeak = 0.7 Vrms

With other daughterboards you will need to calibrate at the frequency
of interest.

Thanks, that's helpful. However, I can't quite make the math work:

P = V^2/R ; 0.01 W = 1^2 / R ; R = 100 Ohms.



RMS power = Vpeak^2 / (2*R)
RMS power = Vrms^2 / R

Matt



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