| ??? 12/27/07 18:32 Modified: 12/27/07 18:37 Read: times |
#148804 - I am not sure... Responding to: ???'s previous message |
...whether the transmission will work at all, with unshielded cables.
Transformers can be used for high frequency transmission, like can be seen here: http://www.hirose.co.jp/cataloge_hp/e22229322.pdf The question is, whether the transformer is able to transmit low frequencies! Maybe the transformer only works with a modulated carrier... The biggest problem I see is the poor cable type. Usually a shield is used when working with such a long cable. The other disadvantage is, that enormous losses will occur and that the characteristic impedance might not be stable enough. Such a long twisted pair cable will only work with proper termination at both ends. So, you would need a 120 Ohm driver and a 120 Ohm termination at receiving end. Can the SSM2142 handle a 240 Ohm load? Also, you might have to play with the termination impedances a bit to obtain best results, because twisted pair can differ between 100 Ohm and 150 Ohm . RS485 says that maximum speed is 9600bit/s with a 1200m long shielded cable. But you try a 4km long unshielded cable... Kai |
