[time-nuts] FE-5680A Results so far
saidjack at aol.com
Thu Dec 29 20:48:30 EST 2011
Tried crystal lattice filters, their bw is usually too large (1 to 2khz)
I would use a simple pll, such as an exor gate driving a single gate vcxo with <10hz bw. Most crystal oscillators would improve the noise from the dds.
So you could do this with four parts:
Nc7sz86 exor gate driven by the dds and the crystal, the output driving a 10uf to 100uf tant cap through say a 10k ohm resistor, feed the signal on the cap into a Crystek 10 MHz vcxo. Done. Use an inverter on the exor output for negative slope vcxos. Use an at cut crystal discrete vcxo to avoid paying for the Crystek vcxo.
An lc filters bw is even worse (10s of kHz)..
On Dec 29, 2011, at 17:53, Chris Albertson <albertson.chris at gmail.com> wrote:
> On Thu, Dec 29, 2011 at 10:37 AM, Said Jackson <saidjack at aol.com> wrote:
>> Good enough as a portable frequency counter reference, as the offset can be compensated, and the output is fairly stable...
>> These units could really use gps disciplining and a crystal post filter.
>> Great stuff for $40, new they must have been over $1000.
> I had actually thought about a crystal latice filter I think I can
> find three 10MHz crystals and put them in series. The trouble is
> I'm not sure what problem the filter might introduce and I don't have
> a way to measure the filter's performance
> I'm thinking of adding an RF amplifier using just one 2n5109 and an LC filter.
> Chris Albertson
> Redondo Beach, California
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