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

Robert Atkinson robert.atkinson at genetix.com
Mon Jul 30 03:38:01 EDT 2007


Hi Jason,
I had the same issue with a SatSync GPS. I got an old attenuator (burned
out or unknown spec), N type in my case but whatever matches your
splitter. I unscrewed it and removed the resistors. I placed a 0.001uF
63V ceramic capacitor between in and out and a load resistor (calculated
to draw just above the antenna warning current) between out (Rx side)
and ground. I did not feel this resistor would affect the signal too
much, but slipped a ferrite bead over the ground end lead just for luck.
It seems to work OK.

Robert G8RPI.

-----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 21:53
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] Building a DC Block Thingy....

); SAEximRunCond expanded to false
m at febo.com

I have 2 other GPS devices already on the splitter, so there is really
need for any DC current to be passed as the splitter will just sink it.
just wanted to build an extra measure of safety in there sinking the 12V
before the splitter *incase* the other 2 GPS devices are turned off or
something happens.

Yes I'll probably plug in the NTS and check the power on the antenna
if it stays at 5V then I can at least use it temporarily to ensure that
working and everything.

I'll look into some of the mini-circuits stuff on eBay and see what I
find. I probably won't buy / build anything until the unit arrives. I
be able just to desolder a component and sink the 12V internally before
gets injected to the RF signal. But I don't want to cut any PCB traces
or do
anything that is irreversible.

Thanks for all your input guys and various solutions. :)

I'm surprised nobody said get a 12V antenna... lol. Does anyone have any
spare outdoor mast style they would sell (cheap)? I remember I saw some
eBay a while back, I'm sure more will pop up eventually.


> My first thought here would be to use a small 3 pin 5V regulator to
> DC down, and then capacitively couple in and out to let the RF
> Interesting to see what other comments you get.
> Rob K 

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