On 07/27/2015 11:56 AM, Jose Perez wrote:
Hi 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
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 UHF
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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