The sub receiver connects to the AUX BNC or the ATU but not both. To correct this I added a toggle switch and mounted it to the ANT3 position. For my application, I needed a way to switch between both inputs. At least for now, I don't need the 2 meter module.
Fortunately, I had spare TMP sockets and a short TMP cable that I pulled from scrapped transceivers. I soldered the sockets to the toggle switch. I plugged in two TMP cables to the outer socket. One went to the AUX BNC and the short TMP cable went to the TMP socket on the ATU. The center socket went to the Sub RCVR BNC. I wrapped toggle switch with copper tape.
In the attached photo, so that I can get a clear shot of the toggle switch, I disconnected the TMP from the ATU.