Power measurements, what am I doing wrong?
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| May 15th 2017, 04:40 | |
ON4DDTotal Topics: 0 Total Posts: 0 |
I have tried to combine a few measurement methods on a signal coming from a signal generator. They don't really seem to agree on the measured power, so I guess I might be making some measurement/thought mistakes. Source: Signal generator: TTi TGR2050, 100MHz, 0dBm out Cable: know good Ecoflex 10 cable Measurements: 1. Tektronix TDS 5054 500MHz scope Terminated in 50 ohms, measured Vpp=0.261V Power: P=U²/R, adds up to 1.36mW or 1.34dBm 2. Rohde&Schwarz FSL Spectrum analyser RBW and VBW set to 300Hz, span 10kHz Peak power: -7.63dBm 3. Rohde&Schwarz URY millivoltmeter with RF sensing head Terminated in 50ohms load -7.67dBm PEP: -7.53dBm Seems I am not measuring correctly, or my understanding isn't deep enough. What am I doing wrong? Regards, Dieter ON4DD |
| May 15th 2017, 10:13 | |
W1VTSuper Moderator Total Topics: 0 Total Posts: 0 |
0.261 volts/2=0.13 volts peak 0.13 volts peak/1.414=0.092 volts rms (0.092volts)^2/50ohms=0.17 x 10^-3 watts or 0.17 mW 10*log(0.17)dBm =-7.7 dBm Zack Lau W1VT ARRL Senior Lab Engineer |
| May 15th 2017, 10:40 | |
ON4DDTotal Topics: 0 Total Posts: 0 |
Dear Zack, Thank you very much. That makes sense and confirms the other measurements. So... I should have my doubts about the signal generator then, correct? Regards, Dieter |
| May 15th 2017, 12:04 | |
W1VTSuper Moderator Total Topics: 0 Total Posts: 0 |
It may be a bad connector. |
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