Tam, W2TT wrote:
"At 70 cm they might both be active."

The impedance of the 2-meter antenna is unknown at 70-cm. With 1/4-wave
or less of cable at 70-cm, velocity factor considered, you should be
able to make the 2-meter antenna appear a very high impedance at the
common point where the 2-meter and 70-cm antennas are oaralleled.

Best regards, Richard Harrison, KB5WZI