Your oscilloscope fft is plotting single-side amplitude spectrum in V/rtHz (dBV/rtHz), this is in contrast to a spectrum analyzer which plots power spectral density W/Hz or (dBm/Hz).
So -2.17 dBv is 10^(-2.17/20) = 0.779 Vrms comparing this to your Vpk-pk measurement 2.3 / 2 / sqrt(2) = 0.813 Vrms That's not to say a scope can't plot power spectrum if the load is explicitly given or assumed 50 Ohms, but in general the plot is amplitude. On Wed, Sep 28, 2016 at 1:38 AM, Tim Lister <lister...@gmail.com> wrote: > On Tue, Sep 20, 2016 at 12:56 PM, Bryan _ <bpl...@outlook.com> wrote: > > May also want to check the output amplitude. If memory serves me correct > it is very common for a capacitor inside this model number to fail. It can > be fixed but requires a torch or a pretty heavy duty soldering iron to get > the can open. > > http://www.rbarrios.com/projects/MV89A/ > > > > -=Bryan=- > > > > I managed to borrow a Tek TDS 2024B 200 MHz scope from work and hooked > it up to the output of my MV89A. I get a peak-to-peak measurement of > 2.3 V which if I have converted it right is ~11 dBm ? Alternatively if > I turn on the FFT mode on the scope I get a peak value of -2.17 db if > I am driving the cursor mode correctly. With the 10 MHz from the > radioshackus GPSDO used for triggering, it takes ~18 seconds for the > MV89 waveform to drift 1 cycle (this is without anything connected on > the Uin or Uref pins). > > Tim > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.