[time-nuts] Normal operating specs of a Morion MV89?
listertim at gmail.com
Fri Sep 30 17:41:36 EDT 2016
On Wed, Sep 28, 2016 at 3:30 PM, Scott Stobbe <scott.j.stobbe at gmail.com> wrote:
> You are certainly no where near -40 dBm into 50 ohms as the blog Bryan
> posted above. Your setup may have 70-80 pF of load (~220 Ohms), if you also
> measured the output voltage with a 10x probe you could work backwards to
> see how close you are to 50 Ohms output.
> Roughly speaking it sounds like it will be in spec for amplitude, but to
> definitive you will have to load it with 50 Ohms as others have suggested.
> Anything can work plug your bnc cable into a 50 Ohm input instrument (even
> if its ancient) and measure the output voltage on the OCXO with a 10X
> probe. Or a near enough to 50 Ohm resistor as Tim suggested.
I obtained a (Pomona I think) 50 Ohm terminator/6db attenuator and
repeated the measurements with the MV89A, connecting the RF and GND
pins through a BNC cable and the terminator directly into the Channel
1 of the scope . I now get an amplitude on the scope FFT of -6.99 dB
measured with the cursors. According to the scope manual this is
referenced to 1 V rms so this would give a Vrms equivalent to -0.99 dB
i.e. 0.89 Volts. Assuming I've done the rest of the maths conversions
right, this would give a peak-to-peak value of 1.26 V and a power of
~11 dBm. (Assuming everything worked alright, I put the scope captures
up on our Owncloud at
https://cloud.lcogt.net/index.php/s/pHBV6EORT33ucjA - Channel 1 is the
MV89A, Channel 2 is the GPSDO output)
So I think this means my unit is behaving OK ?
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