[time-nuts] Normal operating specs of a Morion MV89?
scott.j.stobbe at gmail.com
Wed Sep 28 14:38:52 EDT 2016
If you used a 10x probe (10 Meg || 10-15 pF) you may have a pretty weak
output, but if you could drive a meter of coax or a 1x probe to 800 mVrms
at 10 MHz your probably not too far off spec.
100 pF at 10 MHz is 160 Ohms.
On Wed, Sep 28, 2016 at 12:39 PM, Tim Lister <listertim at gmail.com> wrote:
> On Wed, Sep 28, 2016 at 4:14 AM, Bob Camp <kb8tq at n1k.org> wrote:
> > Hi
> > You have one of the many MV89A’s with an output problem. To be absolutely
> > sure of the output, you need to have the scope set to 50 ohm input. If
> it was set
> > to Hi-Z, the output is likely even lower…..
> It seems that the scope is 1 MOhm input impedance and is not
> changeable. I will have to see if we have any 50 Ohm in-line
> terminators around that I can also borrow. Does anyone think that
> there is any value in trying to pursue a return and replacement with
> the ebay seller (being China, it's likely to be a long round-trip time
> for both messages and parcels) or just live with it and move on
> (potentially replacing the capacitor later if I get some way of
> getting the casing open safely). From what Bob and others have said,
> it seems that most of the MV89's have this problem so it seems
> unlikely I would get a better one without a lot of trials.
> > Bob
> >> On Sep 28, 2016, at 1:38 AM, Tim Lister <listertim at gmail.com> wrote:
> >> On Tue, Sep 20, 2016 at 12:56 PM, Bryan _ <bpl521 at 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
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