Re: goofy frequencies

Florian Teply wrote:
Joerg <notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx> wrote:
Phil Hobbs wrote:
John Larkin wrote:
Suppose I really want a crystal oscillator at, say, 122.167958 MHz.
And I'd like to have the option of phase locking it to some standard
reference, 5 or 10 MHz maybe. And I'd like cheap ones for low-end
products, and TCXO or OCXO stability for better versions.

I can have custom XOs and TCXOs and OCXOs made at great expense. Or I
can lock a VCO to a standard, stock 10 MHz rock.

So what's a good way to do the frequency shift? If we start with a VCO
that's in the 122... ballpark, we could build a DDS that generates 10
MHz from it, sinewave lookup, dac, lowpass filter, and phase detect
the nominal 10 MHz result against the reference 10M and close that
loop. That should work, but is a bit of a hassle.

If we sart to leave out parts, I assume phase noise and such will pile
up.

Any ideas or recommended references?

John

Back in the day, you used to be able to get specific crystal frequencies reasonably inexpensively in small quantities--can you still?

Yes. Best to ask a ham radio operator who still builds stuff (before they are extinct ...) for some good hints where to buy.

Well, over here in good'ol Germany, i can order custom-made crystals for
IMHO reasonable 21 to ~50€ depending on frequency and specials (short
case, 10ppm, oven stuff). So given standard specs would suffice (i.e.
20ppm, 122.167958 MHz, HC25 case) would go for 21€ plus shipping and
handling (6€ to Germany, 9,50€ international). That would be about USD 42.50 based on todays exchange rate. Fairly reasonable for a single
custom-made crystal IMHO.
Supplier would be Germany-based company "Andy's Funkladen",
www.andyquarz.de. Unfortunately, i haven't found an english website of
them though.


Back in Germany I've used another outfit that had better pricing. I believe it was located in the little village of Daun (Eifel Region). But that was very long ago, always under 20 Deutschmarks. Then some outfits in the Netherlands with sometimes even better prices, well under 20 Dutch Guilders back then. 1980's.

For super top notch crystals where price was not an objective we used KVG (Neckarbischoffsheim?).

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
.

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