[time-nuts] HP/Symmetricom 58535A and 58536A

Magnus Danielson magnus at rubidium.dyndns.org
Wed Nov 4 00:00:48 UTC 2009


Hi Said,

SAIDJACK at aol.com wrote:
> Hello Magnus,
>  
> yes, interestingly enough the units I have seem to have the option to power 
>  them through port-1 removed by brute-force: the inductor on all my units 
> has  been ripped off the PCB by force!
> 
> This holds for the 1-2, 1-4, and 1-8 Agilent/Symmetricom splitters I have,  
> all of them have this rather rude modification made (and they are all from  
> different sources, and vintages).

Then the Thunderbolt (and several other GPS receivers) will have a 
problem. They will detect an "open" antenna and fail, regardless of the 
fact that it may be tracking sats.

> Thus port-1 has no DC load at all, while all the other ports have a DC load 
>  to ground for the GPSDO.
>  
> Maybe this is the problem, I need to see if the Thunderbolt works with or  
> without a DC load..

DC-feed it separately and just move port.

Another approach is to put a DC-load-resistor of say 470 ohm in a BNC 
T-connector, preferably with a series-inductor. That will add about 10 
mA of DC load. Kicked a commersial GPS clock alive that badly needed.

> I am glad I am not the only one having this issue with the Thunderbolt  
> though.

I think one should view it as learning how they work. The function is 
actually a safe-guard, but it requires a bit more controlled environment 
than we sometimes allow ourselves to provide. When running under the 
propper condition, it will protect the time of the holdover clock from 
various mishaps where we can expect the sats to be gone or in very high 
  noise condition anyway.

> One more tidbit on the side: it is not a good idea to mix-and-match GPSDO's 
>  that have different antenna voltages (5V and 3.3V for example) on a 
> passive,  DC-coupled splitter. This will create a problem. And can also lead to 
> some  really interesting results:
>  
> I have a USB eval board from a Taiwanese company, and noticed that it  
> generated a 1PPS without the USB being plugged-in. Very strange.
>  
> Turns out the board is getting power and running perfectly well from  
> another GPSDO connected to the same passive antenna splitter, and being fed  
> power from it's own antenna input!!

Now, that is antenna power! :)

Heard on the radio about a professor discussing the possibility to make 
use of the charge of thunderclouds to charge batteries. He and his team 
had developed devices that actually did this and got it to opperate. In 
more tropical environments both heavy thunderclouds and lack of 
electricity for mobile phones and radios is frequent. Also, it was 
fairly cheap, maybe 30 dollars or so.

Cheers,
Magnus



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