If a dipole antenna is resonant on some frequency, F0, then it is not very usable on the frequency F0/2, because it becomes highly capacitive and the resulting VSWR value will be very high.
The situation is not much improved with a 300 ohm ladder line with the length of 1.5m since it only makes a rotation of 12.6 deg at 3.5MHz on a Smith Chart.
rotation=1.5/(300/3.5)*2*360=12.6 [deg]