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

[Gerhard Hoffmann]

Am 10.03.19 um 15:54 schrieb jimlux:

> True.. but there are a plethora of the USB 5V power blocks around - in 
> general, there are lots of USB 5V (noisy, I'm sure), e.g. Cars now 
> have 5V USB jacks, so I was thinking about designing with that in mind.
>
> The question is really more one of "how much filtering do I need to 
> design into the downstream power supply circuits"

It should not be too hard since there are no ground loops involved.


>>
>> < 
>> 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.

BTW, the next picture to the left is the noise of 2 cells = 8Vdc.

14 dB below 1 nV. The steep rise below 30Hz is the too small coupling 
capacitor.


> for all practical purposes any legitimate 18650 sized Li-ion cell is 
> around 3.5 Ah.
yes. the really good ones.

>> (who thinks about using a dozen of these for portable EME tests on 
>> 432 :-) )
>
> You're going to run your kilowatt amp off 36 cells in series? Why not..

No, 100W from a GaN FET at 48V and <= 10 element antenna is more than 
enough.

The rest is mostly a Dell XPS13 notebook and a Red Pitaya + up/down 
converter.  Lunchbox size.

< https://www.redpitaya.com/   >


It is easy when your partner station looks like this:

> < http://dl7apv.darc.de/Neue%20Antennen/Neue%20Antennen.htm   >


To be more on-topic, two Red Pitayas can be synced and should easily

provide the hardware for a Timepod work-alike. That would be 4 125 MSPS 
14 Bit ADC channels,

two FPGAs and ARMs with Linux and web server.

(and with dual use as VNA, Bode plotter, signal generator...)


regards, Gerhard