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[wxsig] Standing waves WX station

Don Jeerings djeerings at tampabay.rr.com
Sun Oct 22 19:22:04 UTC 2006


Just a comment about the standing waves on the RS-232..  Do a little math, At those frequencies a wave length is 6 to 8 thousand feet long. I am not familiar with that WX equipment but stand standing waves IS NOT YOUR PROBLEM.

 I call to your attention that Bridging two units  to to-gather can cause some impedance mismatches, some power losses and communication protocol problems.

Keep in mind that a  three terminal RS 232 system has to include some communication protocols like addressing etc .i.e. the host must address each terminal in turn and then clear them to send or else they will walk on each other when transmitting. With a two terminal system addressing is not necessary because the host knows there is only one terminal to answer.  I suspect a software problem where your host cannot identify which sensor is talking. (may be both sensors are talking at the same time) . This will result in a complete communications failure. (time out) 

Don Jeerings     KI4EFL


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