[time-nuts] Valpey-Fisher VFT22H OCXO Output

Bob Camp kb8tq at n1k.org
Sat Jan 30 09:33:45 EST 2016


Hi

Unless it’s a really weird termination impedance, it’s broke. The SMA is a pretty 
good indication that it *should* work into a 50 ohm load. 

The only other possibility is that your probe is taking the load far enough off of 50 ohms
to mis-tune the output filter. I’d set the scope to 50 ohm input and cabe the output directly to it.
If that’s not practical, put a 6 db 50 ohm pad on the output of the oscillator and see what it 
looks like after that. 

Bob


> On Jan 29, 2016, at 10:19 PM, Logan Cummings <logan.cummings at gmail.com> wrote:
> 
> Hi All,
> 
>     Curious what could give this waveform (attached) - I presume this is
> not correct output for this oscillator (surplus/salvage from Harris
> Constellation receiver).
> 
>     Frequency looks OK with +2V EFC but output looks like neither sine nor
> any CMOS I've seen into 10Mohm (first capture, scope probe alone) or 50ohm
> (50ohm term at SMA connector, probed by same scope probe) .
> 
>     What gives? If I open up the can, what am I looking to possibly
> replace/eliminate? How to open it? It's soldered shut (2x2in case).
> 
>     I need a good low-noise 100MHz sine wave for my application so I'm
> tempted to open this guy up and replace the output circuitry with something
> more suitable.
> 
>    Thanks in advance for any pointers/info on these units!
> -Logan
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