[ntp:questions] Very large jitter and offsets on GPS ref clock after upgrade to "p5"

John Hasler jhasler at newsguy.com
Mon Jan 9 01:06:02 UTC 2012


unruh writes:
> He said he was using 80 ft of cat 5 cable. That is 100 ohm cable. To
> get rid of reflections he needs a 100 ohm termination. This has
> nothing to do with 232.

RS232 is not intended to be used with speeds and cable lengths such that
transmission line effects are significant.  When properly implemented
(it usually isn't) risetime is limited with rc networks to prevent
ringing and the output impedance of the drivers is such that they can
withstand a short circuit without damage.

-- 
John Hasler 
jhasler at newsguy.com
Dancing Horse Hill
Elmwood, WI USA



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