[Elecraft] OT- RS232 CARD input clamped to 2.5V

[Brian Alsop]

Guys,

Looking for some insight.

I was doing some checkout of a device.  The device output a +10/-10V 
RS232 signal swing from a MAX232 device.

When it was attached to a PCI serial port card, the output dropped to 
+2.5/-10 V.  In other words, the PCI card was clamping the input 
positive value.  It does work OK even clamped like this.

I'm guessing the internal chips are low voltage devices.

I though one of the redeeming values (for hams at least) of the +15/-15 
volt RS232 spec was noise immunity.  Clamping it to 2.5 Volts means 
considerably less noise (RFI) immunity?

True we do get along with lots of 5V TTL stuff.

73 de Brian/K3KO



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