So, you are using the wrong connector. You need to connect to the "data" connector on the back of the transceiver body, not the control head.
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Also, the "speaker" level on the Windows mixer is your transmit audio, not receive. You need to switch to the "Recording" tab on the mixer and adjust that level for receive. While you are there, select the Custom tab and uncheck the AGC option.
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-Scott, NS7C
Scott Currie