Monday, April 20, 2009

W4BXI System Audio

W4BXI has gradually built a versatile interconnection of components that enable him to hear audio from two transceivers and to interface two-way audio between a transceiver and his contacts using Skype for VoIP calls via the Internet. Of course, he also incorporates the 20th century phone patch as another option.

As John's system has grown some issues have emerged about how to best interface various components while avoiding ground loops, feedback and level mismatch. Recent email exchanges with W4UOA and WA5MLF led to their developing some system diagrams to aid in discussion and identification of configuration choices. Below is a diagram from W4UOA that gives a complete picture of the capabilities assembled by W4BXI. (Click on it to enlarge.)

This shows that John can access various audio streams at the mixer as well as participate in a Skype VoIP conference via the Bridge Computer. Carl has included a list of control operator procedures describing how the main components are used. In testing today John determined that he can also initiate a Skype conference on the Rig Computer and connect those participants to his FT-1000 transceiver.

In order to focus more closely on the two-way audio paths, WA5MLF prepared the diagram shown below that does not include all components and audio mixer connections. (Click on it to enlarge.)
The audio mixer is shown with its separate left and right channel inputs from the FT-1000 and outputs to a headset. A new input to the headset's right earphone is the Skype caller's talk path (dashed line in the drawing). Phone patch #4 is used to combine the talk and listen (transceiver transmit and receive) audio while avoiding the creation of a feedback path. Phone patch #2 is used primarily for ground loop isolation, and can be replaced by a single transformer.

Comments and suggestions are welcome.

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