[TenTec] Omni VI & SignaLink USB

[Bob McGraw - K4TAX]

I'm trying to assist a friend setting up his Omni VI with a SignaLink USB.  He does have the cable supplied from SignaLink and it seems to be connected to the radio correctly.  It receives and decodes PSK-31 very satisfactorily and it keys the transmitter correctly. 

The difficulty is having both the SignaLink connected to the Audio IN on the rear and the microphone connected to the front at the same time.  The SignaLink appears to key the radio correctly but does not produce output.  When he then later and on a different frequency tries to transmit SSB only white noise is heard.  If he unplugs the cable to/from the SignaLink the noise is not heard. This occurs when the SignaLink is off or on.

It appears from the schematic the mike input on the front and the rear Audio In are each isolated by a 10K series resistor to a summing point at the mike amp input.  Using a low impedance {500 ohm} dynamic mike and the SignaLink output being some 600 ohms, I calculate the isolation between the two inputs would be some 35 dB or so. Certainly this would seem to be very adequate isolation such that having the two connected, although the SignaLink is off, it would not interfere with the use of the mike.  And with the SignaLink on it would produce audio and it would not be interfered with the connected mike.  

Anyone have any specific experience or thoughts on this configuration?

73
Bob, K4TAX