Computer to rig interface question

[KU4UV]

I don't know if this is the correct forum for this question, so excuse me if it isn't.  I have a question about adding a microphone connector to a interface cable that I constructed from plans I found on the Internet.  I have an interface that I built a couple of years ago that uses a Radio Shack isolation transformer to seperate the transceiver from the computer.  One end of the interface connects to the soundcard output of the computer.  The other connection plugs into the microphone connector on the front of the radio.  I use this interface for digital modes such as PSK31 and RTTY.  I have a TS-130SE transceiver, and I use the transceiver's VOX circuit to key the rig.  
     What I am wanting to do is simply add a 4-pin mic connector to this interface so that I can also use my microphone without having to unplug the interfacfe cable.  I am wondering if it is o.k. to just go ahead and wire up a 4-pin mic connector to the female connector that plugs into the transceiver, and then just plug my mic into this connector without it having any problems?  This is similar to what the Rigblaster interaces have, in that there is a microphone connection on the front of the interface, and then a microphone output connector that plugs directly into the transceiver.  It seems to me that thiswould fine, but I thought I should check first.  Can anyone give me any tips or advise as to whether it is o.k. to do this?  I have so far not had any issues with RF getting back into the laptop, but then I only run about 30 Watts on the digital modes, and never more than 100 Watts.  I have a voice keyer program that I am wanting to use, and I want to be able to use my microphone also for answer any CQ replies.  Thanks for the help!

Michael KU4UV
ku4uv@arrl.net

[WI7B]

Michael KU4UV,

Nope, this isn't the right forum.  The Computer forum is probably where you wanted to send this query. But, I can take a stab at an answer.

The interface you built probably includes both the Radio Shack isolation transformer and the audio output transformer.  The difference between them is the isolation transformer is just that.  It's a 1:1 transformer to isolate two I/O circuits that share a similar impendance. This is used between the line-out of the PC and the microphone of your rig (high-to-high I).  

The audio output transformer is an 8 ohm to 1000 ohm transformer that not only isolates the circuits, but steps up/down the impendance.  This type transformer is what you need to go from your rig's external speaker output to the line-in input of the PC (low to high I).

So, the 4-pin microphone would be added to the rig side of the isolation transformer. This will not even be a problem as long as you: (1) disconnect the microphone before moving to PSK31/VOX, and (2) disconnect the line-in to the PC when moving to voice.

73,

---* Ken