[Elecraft] K3S RS232 "Y" Connector causing port conflict

[Josh]

The OM2500A has 2 serial ports. It is designed to be patched inline between a computer and the K3. 

73,
Josh W6XU

Sent from my mobile device

> On Dec 14, 2015, at 5:11 AM, Don Wilhelm <w3fpr at embarqmail.com> wrote:
> 
> Charles,
> 
> I don't know the specifics of your OM2500A amplifier, but I do know about RS-232.
> First, RS-232 is a point to point system.  The use of "Y" connectors is not the norm and are applicable only under certain specific conditions.
> Those conditions are that the device added by the "Y" connection has no active drivers on the RS-232 signals - only line receivers are permitted.
> 
> Think of it this way - a driver on an RS-232 line can have a negative voltage of up to -25 volts, and a positive voltage of up to +25 volts.
> Imagine that one driver is trying to produce -25 volts while the other driver is trying to produce +25 volts.  In other words, they 'fight' with one another, and the result is 'confusion' because the receiver listening on that RS-232 signal line will not respond to a voltage that is less than 3 volts positive.
> 
> In other words, use a "Y" connector only when the added device is capable of being put into a "listen only" mode (with its drivers disabled).
> Look at your amplifier information carefully to see if it can be placed in a "listen only" mode.  If not, you cannot use it with a "Y" connector.
> 
> The SteppIR is one example of a device that can be placed in listen only mode, so the use of a "Y" connector is possible, but that is not the general case.
> 
> Bottom line, you can connect only *one* RS-232 device to another in the general case.  Introducing a 3rd RS-232 device (with a "Y" connector) requires special conditions be present in that 3rd device - it must only listen to the data traffic and not attempt to transmit data.
> 
> 73,
> Don W3FPR