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

timeok at timeok.it timeok at timeok.it
Tue Nov 27 14:30:38 UTC 2018


   Dana,
   As described in the following HP GPS splitter the isolation is  > 40dB.
   https://www.febo.com/time-freq/gps/hp58516a/HP_58516A.pdf
   I use one of these 8-channel splitters.
   I had a bad experience using a passive splitter of the minicircuits in the 10MHz distribution in my lab.
   An instrument that accidentally generated instead of receiving the reference disturbed all other related instruments.
   In this case, an isolation of 25-30dB proved to be insufficient.
   Therefore, I recommend using a GPS splitter with active components such as the classic HP models and other brands.
   Luciano
   www.timeok.it


   Da "time-nuts" time-nuts-bounces at lists.febo.com
   A "Discussion of precise time and frequency measurement" time-nuts at lists.febo.com
   Cc
   Data Tue, 27 Nov 2018 07:44:23 -0600
   Oggetto [time-nuts] RF isolation requirements for multiple GPS receivers
   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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