I don't believe that RCT is what you're looking for to set the timing for your radio. If you want an external clock source I would recommend looking into a GPSDO (GPS Disciplined Oscillators). You can find those for about $50-200.
If you want a good US made TCXO that won't brake the bank you might be better off building your own...
https://github.com/osqzss/gps-sdr-sim/tree/master/extclk