By minimizing of plate current, gm of the valve is made smaller. It is a technique to use a high gm valve safety. This IF amplifier has 20dB gain. Antenna signal is connected on a grid of ECO oscillator. Therefore this valve acts as a self oscillating convertor.
Some oscillating signal is projected by the receiving antenna.
This convertor has 13dB gain. I could hear some broadcasting station in Tokyo from Ibaraki Japan with 10m wire antenna. This Radio is useful enough as a home radio.