Hi Said,
[email protected] 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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