[time-nuts] Wenzel oscillator - L1 value?

Philip Pemberton lists at philpem.me.uk
Sun May 4 07:30:43 EDT 2014


On 24/04/14 23:30, Bob Camp wrote:
> There is no difference at all between a 32 pf series crystal and a 32
> pf parallel crystal. They both resonate with a 32 pf load and operate
> at exactly the same frequency into that load. Your crystals will work
> fine with that circuit.

That's good to know.

I'm actually testing with one of these crystals:


http://uk.farnell.com/multicomp/hc49u-10-20-50-60-30-atf/crystal-hc-49-u-10-0mhz/dp/1666972

On the basis that they're cheap and I don't want to ruin one of my OCXO
crystals. Said OCXO crystals came from QuartSLab, with the following
specification:

  Crystal Frequency: 10.00000 MHz, Fundamental Mode
        Holder Type: HC-49/U
 Circuit Conditions: Parallel Resonant
   Load Capacitance: 33 pF
   Oven Temperature: 50 Celsius

Those things cost £17 each and had a 20-day lead time last time I bought
one, so I'm keen to avoid damaging them!

They're probably not fantastic compared to a 10811's SC-cut part, but
this is only intended to be a learning experience. I'd consider it "good
enough" if it could hold its own against my LPRO.

The invoice calls them out as "10.00000 HC49 S03F1" -- I'm honestly not
certain what "S03F1" indicates.


> The big claim to fame of the circuit shown is that you can get a nice
> looking sine wave out of it at a pretty big peak to peak voltage.
> It’s not bad for phase noise, but it’s also not the “super quiet”
> that you would expect if you paid kilo bucks for a Wenzel OCXO.

I'll probably be mating it to a 50-ohm driver of some description, then.
That's a job for later, I need to make the oscillator work first :)

For now I just need to keep it under +24dBm into 50R (limit of my
spectrum analyser), preferably less than +13dBm (1V over 50R).

Thanks,
-- 
Phil.
lists at philpem.me.uk
http://www.philpem.me.uk/



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