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

[Pete Smith N4ZR]

Sure.  I've been dealing for years with 3.3 volt parallel port cards.  I 
think that the noise immunity is much more a function of good design 
than the voltage level.

73, Pete N4ZR
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On 3/15/2013 3:40 PM, Brian Alsop wrote:
> 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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