RF splitters, and friends

Paul Theodoropoulos paul at anastrophe.com
Fri Jul 5 19:52:16 UTC 2019

So, I'm thinking of buying an RF splitter, so that I can feed my three RPI 
ntpsec servers from my one, best antenna.

There's a ton of pretty generic SMA splitters on both Amazon and ebay, 
prices are reasonable, but it's always a crapshoot with the Shenzen world 
of knockoffs.  And with vanishingly little RF background, I'm finding 
myself overwhelmed with both too much info, and often too little info 
making for too many iffy choices.

That said, here's an example device I'm likely to get:


Okay, that's a start. As Gary Miller has advised, I'll also need DC blocks 
for all but one of the outputs. The problem here is that there's a lot of 
'shorthand' used in the descriptions of them, and I'm at a loss as to what 
the right device would be. For example:


  * They're DC blocks: check.
  * They're SMA: check.
  * They're male-female: check
  * They're listed as "DC-6.0GHz". Er, taking that at face value, it means
    they block from DC all the way to 6GHz, which would do a great job of
    blocking the GPS signals as well. But I *think* they mean 'DC block,
    passes everything else up to 6GHz' - since it seems unlikely they'd
    only pass signals *above* 6GHz. I'd expect it list a range over 6GHz
    if that was the case....??
  * They're also available in fixed attenuations - 1db, 2db, 3db, 5db,
    6db, 10db, 15db, 20db, and 30db! Well, uh...here I have zero clue - I
    wouldn't want to attenuate the GPS signal, so, 1db? Or is it a
    function of how much power is being injected by the GPS device,
    so...5v into 50 ohms, multiply by 3.14159, divide by today's S&P 500 +
    the phase of the moon, I think...

Paul Theodoropoulos

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