Dear all, I generated a 50 MHz, 10 dBm sinewave
using a Rohde & Schwarz RF signal generator.
I checked this using an Agilent spectrum analyser
and, as you'd expect, I get my tone at 50 MHz with
peak amplitude of 10 dBm. However, when I input
my RF signal to a TDS 210 Tecktronix Digital Oscilloscope,
the peaktopeak voltage is 336 mV and the Cyc RMS
voltage is 117 mV. Now, on the TDS210, Cyc RMS calculates
the RMS voltage over one complete cycle of the waveform.
When I tried to calculate this I got a different
answer:
P = 10 dBm, which is equivalent
to 100 uW Now, P = V^2 / R I've taken R =
50 ohms Therefore Vrms = sqrt(P x R)
That
is: Vrms = sqrt(100 uW x 50 ohms)
So, Vrms
= 70.7 mV
This is different to the 117 mV
measured on the oscilloscope??
