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NNTP-Posting-Date: Tue, 22 Oct 2002 16:40:21 -0500
Subject: Re: RS-485 termination
Date: Tue, 22 Oct 2002 16:50:35 -0500
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> I'd be very surprised if the RFI is coming from the current loop
> switching edges. Are you sure the cable is screened properly
No...I'm not using shielded cable and want to just use
unshielded twisted pair.
The RF isn't bad but bad enough to be induced into a
neighboring cable...I just want to make it perfect and eliminate any source
of emmision completely.
RS485 should do that for me, right?
I know it cancels noise INTO the twisted pair but will also inhibit RF
EMMISION from the cable? (Using unshielded?)
> Use ONE 100 ohm resistor termination, somewhere at the far end of the
> bus. Then just tag the receivers on with short stubs.
I don't follow that term, "short stubs"?
Are you meaning addressing them or something?
This setup is going to be one constant transmitter and always enabled
> In most cases, you'll get away with no termination at all at 1200 baud.
> If the ringing on the edges causes an RFI problem, put resistors in
> series with the outputs. (Slew rate adjustment?)
Pardon my ignorance, I've never really delved into the world of line
drivers/rcvrs before. Thought about using the SN75176.
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