); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] Jason Rabel wrote: > I have a NTS-200 on the way, but one thing about them is their GPS power > output is 12V instead of the usual 5V. I really didn't want to modify the > board any in an irreversible fashion so I was hoping to build an inline > coupler that I could block / sink the 12V current. > > I have a Symmetricom SmartSplitter, and I know that *should* do the job as > long as a lower numbered port is supplying power, but I really don't want to > take the accidental risk of sending 12V to my antenna. > > Doing the math to sink 25ma of current would require a 480 ohm resistor... > That should make the receiver happy and think all is well. But that's as far > as my knowledge goes. What size capacitor would I need to use? Do I need to > add an inductor in series with the resistor? > > > Jason > Jason
Using a resistor may not be such a good idea. It all depends on the antenna preamp circuit configuration. The safest and quietest way is to use a 5V series regulator inconjunction with a couple of inductors and a few capacitors. In principle a series zener (shunted by an RF bypass capacitor >=100pF??) to drop the voltage to around 5v despite the inevitable spead and temperature dependence of the antenna amplifier bias current. It may just be simpler to use a bias T and an auxiliary 5V supply for the antenna. Bruce _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
