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From: | Marcus D. Leech |
Subject: | Re: [Discuss-gnuradio] Power output RFX2400 and OFDM example |
Date: | Mon, 27 Jul 2015 12:55:37 -0400 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 |
On 07/27/2015 11:56 AM, Jose Perez wrote:
There's no way to know precisely what your output power will be, just from the magnitude of the baseband samples. In RF, particularly in UHFHi all, I am trying to obtain or know how much power output my hardware device is transmitting. For this, I am running the example "tx_ofdm.grc" with a USRP1 and RFX2400 daughterboard. The RFX2400 provides a typical power output of 50 mW => ~ 17dBm. The block "Multiply const" can increase or decrease my transmitted signal and I am also using a Spectrum Analyzer to measure the received signal according the distance. Actually, I need understand how the "Multiply const" block relates with the power output ... and what is the exact power that my hardware is transmitting. If I put 0,5 in "Multiply const" block this means the I am transmitting half of my all power output? Thank you in advance. Cheers, José
and above, there's *always* device-to-device variability of 1 or 2dB.Now, since power is proportional to the square of the voltage, and since baseband samples represent instantaneous voltages, then increasing your baseband magnitude from 0.25 to 0.5 will increase the *power* by 6dB (factor of 4). As you approach magnitudes of 1.0 it's likely that the TX amplifier will be close to its compression point, the exact point can only be verified with external measurements.
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