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Kiwi GPS - connecting two, one antenna, no fancy splitters.

Somwhere in the back of my mind I remember something about GPS needing a load to be enabled?
Am I dreaming that or is it no longer required? (searched the forum for a while)

I got round to sticking two Kiwi's in one aluminium hard drive case and was concerned about putting a T-piece between the GPS inputs and one antenna due to the supply voltage from both.
I've got passive splitter somewhere but I'm running out of SMA - other adapters so can T SMA be used safely with dc path? I know it is only 3.3V circa 30ma but I didn't want the supply from one making the other think nothing was connected.
I just tried with a spare Bias-T that breaks the DC path from the second Kiwi and it seems to be all working but I keep remembering some detail about sticking a resistor across the GPS without a load?

Comments

  • jksjks
    edited January 2019
    No, not an issue.

    Aside from a few Beta test units all Kiwis have a 100K resistor (R104) across the "GBIAS" signal on the gps chip (not the same as across the gps antenna input which would not be ideal). See schematic: http://kiwisdr.com/docs/KiwiSDR/kiwi.schematic.pdf

    This was the one and only issue that caused a board spin. You'll see in some photos boards marked "March 2016", but the production units are all marked "May, 2016" and have the fix.
  • Brilliant, that resistor is probably what I remembered but could not remember the context and searching gave just too many general hits.
    Thanks
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