I have found that just using two resistors as an
attenuator pad between the sound card and the audio
input on the rear of my PRO II worked just fine. I put
them in a DIN-5 jack that fits in the ACC port on the
rear just fine. I use computer control for the PTT
function so I have no audio interface box at all. I
just made a custom cable that connects between the ACC
plug and the sound card. The two resistors used are
10K and 100 ohm. Here is the link to a good interface
detailing this circuit.
http://www.qsl.net/wm2u/interface.html
Icom transceivers have properly isolated circuits
connected to the rear of there input and output jacks
so adding a second set of isolation circuits is just
making things more complicated and expensive.
--- Rick Williams <[EMAIL PROTECTED]> wrote:
> I am making a sound card interface for my ICOM 756
> series rig. I have used a
> Radio Shack car stereo dual isolation transformer
> (potted monolithic type)
> package for many years with my Ten Tec Pegasus. I
> now plan to put the
> transformers in a metal box with inputs and outputs
> and wire the sound card
> side with stereo 1/8" jacks and the output to the
> rig with probably a stereo
> 1/4" phone plug or something that has ground and two
> wires.
>
> I just realized that if I mount these in a metal
> box, the ground side will
> be connected between the rig and the computer since
> they will no longer be
> isolated.
>
> Have any of you found that you need to use insulated
> bushings or otherwise
> isolate one side of the circuit so the metal case
> does not act as a
> conductor for the ground?
>
> Or have you found that it works fine with the case
> grounding both sides?
>
> 73,
>
> Rick, KV9U
>
>
>
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