[ntp:questions] Oddities in termination of cable from gps18.

unruh unruh at invalid.ca
Thu Feb 23 21:47:28 UTC 2012

On 2012-02-23, Chris Albertson <albertson.chris at gmail.com> wrote:
> On Wed, Feb 22, 2012 at 10:35 PM, David J Taylor
><david-taylor at blueyonder.co.uk.invalid> wrote:
> Also while many RS232 ports will accept TTL signals, if they do they
> are operating way off spec and you are just lucky it works.  You

No, there is the RS232 spec, set up 20-30 years ago, but since the late
80s almost all rs232 receivers have used something like .5V and 1.5V as
the transitions. In part to ease use of TTL voltages. The more relevant
question is not whether the rs232 are out of spec, but do you know of
any rs232 receiver chipsets which do not work with TTL type signals. 

> really should be sure the PPS, TX and RX signals are at rs232 voltage
> levels.  out of spec voltages and long cables are a bad combination.
> I've converted to rg58 drives with 50R driver for the PPS and then
> convert is very close to the computer to RS232.  No ringing.
> Chris Albertson
> Redondo Beach, California

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