On Wed, Sep 28, 2016 at 11:46 AM, Tom Miller <tmiller11...@verizon.net> wrote: > Just put a 47 or 56 ohm resistor from the output pin to ground and look at > it with a X10 scope probe. > > Do you get a sine wave? Over 1 volt pp?
Hi Tom, Scott, I used about two feet of a (Pomona) coax to minigrabbers test lead and connected it direct to the scope and set the attenuation to 1x in the channel menus. I attached the minigrabbers to the RF and GND pins on the Morion since I didn't fancy holding a probe near the ~50 degree C Morion case.. I got a nice clean sine wave and the in-scope measurement routines reported 2.3 V peak-to-peak. I had 1V/div set so I could fit the OCXO and GPSDO outputs on the scope screen for comparison. (I haven't been able to get a screen capture yet as I need to find a small enough capacity USB key that will be supported by the scope) Tim > > Otherwise, you can open up the can and replace the output chip capacitor. > > > Regards > > ----- Original Message ----- From: "Scott Stobbe" <scott.j.sto...@gmail.com> > To: "Discussion of precise time and frequency measurement" > <time-nuts@febo.com> > Sent: Wednesday, September 28, 2016 2:38 PM > Subject: Re: [time-nuts] Normal operating specs of a Morion MV89? > > > >> 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 <lister...@gmail.com> wrote: >> >>> On Wed, Sep 28, 2016 at 4:14 AM, Bob Camp <kb...@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. >>> >>> Tim >>> >>> > >>> > Bob >>> > >>> > >>> >> On 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.
