[time-nuts] RF isolation requirements for multiple GPS receivers

Bob kb8tq kb8tq at n1k.org
Tue Nov 27 15:23:16 UTC 2018


Hi

I’ve run …. errr … lots ( > 40) of GPSDO’s on a common antenna with a single 
amp and passive splitters. I’ve never seen any issues. That includes cases
with multiple ports un-terminated ( so not terrific isolation). 

Bob

> On Nov 27, 2018, at 8:44 AM, Dana Whitlow <k8yumdoober at gmail.com> wrote:
> 
> I want to run about 4 separate GPS units of disparate
> manufacture from a single antenna.  My plan is to
> provide power for the antenna via a bias tee (power
> inserter) at the bottom end of the antenna's cable, then
> use an isolating splitter on the receiver side of the bias
> tee to split to the various receivers.
> 
> My question is: how much isolation between receivers
> is likely to be necessary?  Real life splitters are only
> so-so in isolation performance (15-25 dB), and may
> e significantly worse if the antenna's LNA's output is
> a poor match.  So I'm wondering if I'm going to need
> more amplifiers in the splitter's outputs just for the sake
> of adequate isolation between the GPS receivers.
> 
> Thanks,
> 
> Dana    K8YUM
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