Re: simple frequecny multiplier


"John Larkin" <jjSNIPlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in
message news:b6ka511h2lrb9v09flm6tblohsmscamh4h@xxxxxxxxxx
> TCXOs have a temperature transient problem: the temp comp sensor never
> has the same thermal time constant as the crystal itself, so whereas
> the compensation averages very good, a millikelvin delta-t over 100 ms
> can cause a lot of phase shift. A good OCXO will have a huge thermal
> isolation system and also operates the crystal at its "turning
> temperature" where the inherent TC is zero. All that makes a huge
> difference in close-in phase noise. If you use a TCXO, put it in a
> heavy aluminum can to slow down temperature transients; that alone can
> cut thermally-induced phase noise 10:1.
>
> A good SC-cut OCXO is a few hundred dollars new and is the best you
> can do without going atomic. You can get a used rubidium for about the
> same, but I'm not sure the short-term stability is necessarily better
> than the SC.

I gues ive been looking at to much of the sales blurb, .. yes a good thermal
slug and wind proofing might be a good idea, also the device is basicaly on
its own exept for decoupling and is lightly loaded. its also all on a single
SMD chip.

i had considered OCXO or puting a peltier device to keep it at constant
temp, maybe even at its lower temp turning point. even the idea of having a
temp sensitive oscilator as a sensor and using a PLL to keep the temp
constant. however low power batery operation would make things a lot easier.
however thinking about it i might wel have to resort to a ocxo. the whole
thing should fit into an aluminium or steel tube.

lots of things i havnt realy considered seem to be poping up i gues il just
have to try it now and see just how much everything adds up. theres not
actualy a great deal to it.

> Considered an optical interferometer ?

yes i am thinking about that, however i cant simply use the same light
source and bounce it back to meet the original as this would cuase an
imeasurable result, the Sagnac effect is measured with a single source, but
i would need 2 lasers and be able to tune one of them and keep it in synch
with the other one. im not sure how feasable this is. maybe two closly
matched laser diodes cld be kept in synch by controling the temperature, i
gues they must have some temperature sensitivity.

Colin =^.^=



.

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