Using a DVB-T dongle as an SDR for an Yaesu-857d requires that you sniff the first stage IF signal (68.33 MHz) from within the radio. Many websites show how to solder the sniffer to the radio. This is technically a modification of your radio, and thus not permitted if you're a Foundation Licensee.
Lewis, VK6OI suggested that instead of directly coupling the radio, we might use a toroid tuned circuit and sniff the IF that way.
The suggestion is to wind 10 windings of insulated wire around a high density circular toroid and connect a 10-15 pF variable capacitor in parallel, and then tune the circuit to 68.33 MHz and feed that into the SDR.