[time-nuts] Normal operating specs of a Morion MV89?

Scott Stobbe scott.j.stobbe at gmail.com
Sat Oct 1 16:08:39 EDT 2016

If you used a 6db pad in conjunction with a 50 ohm termination you are spot
on. If you used a 6dB pad as a 50 ohm load, the effective load will be a
bit higher than 50 and the attenuation less than 6 dB. Either way sounds
like the output stage of your OCXO is in spec for 7 dBm into 50 ohms.

On Friday, 30 September 2016, Tim Lister <listertim at gmail.com> wrote:

> On Wed, Sep 28, 2016 at 3:30 PM, Scott Stobbe <scott.j.stobbe at gmail.com
> <javascript:;>> 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 ?
> Cheers,
> Tim
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