[time-nuts] Building a DC Block Thingy....

Rob Kimberley rk at timing-consultants.com
Fri Jul 27 15:33:03 EDT 2007

My first thought here would be to use a small 3 pin 5V regulator to drop the
DC down, and then capacitively couple in and out to let the RF through.

Interesting to see what other comments you get.

Rob K 

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Jason Rabel
Sent: 27 July 2007 20:12
To: 'Discussion of precise time and frequency measurement'
Subject: [time-nuts] Building a DC Block Thingy....

); SAEximRunCond expanded to false
time-nuts-bounces+rk=timing-consultants.com+rk=timing-consultants.com at febo.c

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?


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