[time-nuts] Power supply for OCXO using "USB power blocks"

[Gerhard Hoffmann]

Am 10.03.19 um 01:38 schrieb jimlux:
> Has anyone tried a +5V to +15V DC/DC to run an OCXO, getting the 5V 
> from one of those rechargeable USB power bricks.  I was thinking about 
> portable operation.
>
> In my case, the OCXO is something like a Wenzel streamline. I would 
> think that the DC/DC probably has some noise, but maybe DC/DC to a 
> higher voltage, then a good linear regulator to clean it up (or would 
> the radiated noise just leak around).
>
> How quiet is the output from those USB battery things..I've used one 
> to run a RTL-SDR, but that's hardly a ultimate low noise receiver.
>
That's impossible to predict. These boxes normally contain one Lithium 
cell and a DC/DC converter to 5V.

Its output noise depends on the skill of the designer and the mood of 
the bean counter. It is probably

not a high priority. Also, there my be "effects" from the interaction of 
their switcher and your's.

And the efficiencies multiply.

BUT:

3 of these Li cells deliver 12V in ultimate quality:

< 
https://www.flickr.com/photos/137684711@N07/39972841815/in/album-72157662535945536/ 
 >

The squares on the paper are 5mm.


Noise density is better than 1nV / rtHz above 100 Hz. You definitely 
need a fuse.  Ishort is >> 30A.

This Panasonic type is OK. There are lots of others on the market that 
claim twice the power capacity

but it's a blatant lie.


regards, Gerhard

(who thinks about using a dozen of these for portable EME tests on 432 :-) )