[time-nuts] VCXO help

John Ackermann N8UR jra at febo.com
Fri Feb 25 13:46:04 UTC 2011


Bert, first of all I'm really happy you're digging into this -- it's 
been on my list of "projects for someday" for a long time!

One thing working in your favor is that the actual BFO frequency is way 
down at audio; the BFO crystals at around 2 MHz are divided by 1000 
before hitting the mixer.  So that gives you 40dB of help on the phase 
noise, as well as reducing any frequency offset that DDS step size might 
impose.

John
----

Tijd Dingen said the following on 02/25/2011 08:02 AM:
> Well, I know Geraldo Lino de Campos on this list is using an ICS670-03 for
> this purpose. For me personally that part is too jittery by about a decade,
>
> but for your purpose it might just be the right compromise. Certainly has a
> friendlier package.
>
> datasheet:
> http://www.idt.com/products/getDoc.cfm?docID=18461996
>
> Slight detour about soldering QFN's for prototyping. It is not /that/ bad.
> I will admit that when given the choice between QFNs and TSOPs I will pick
> the latter, but QFNs are do-able. All it takes is patience and a Can-Do
> attitude. Well, mainly patience really. ;) You can do those QFNs for example
> dead bug style on a solid copperclad ground plane. The trick then is to use
> aluminum foil to cover the pads you already soldered, and fluxfluxflux.
> You can put the decoupling caps real close in a sort of stonehenge around it.
> Like I said, requires a bit of patience, but it's fun when it actually works,
> plus you get better at it pretty fast. :)
>
> regards,
> Fred
>
>
> "Bert Kehren" wrote:
>
>> Thanks for the info Fred
>> The problem is the package. Looking at the Cirrus Logic CS 2300-CP and use
>> a bubbler. Since I start out with 5 or 10 MHz there must be something out
>> there  that can be soldered.
>
>
>
>
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