Help with 144Mhz small signal amplifier not amplifying
Try backing off on the collector current say to 5 mA. The Gain-Bandwidth product is sagging at 20 mA. At 5 mA looks like the maximum achieveable gain of the BF240 is about 900/144 = approx 6.
Also consider using a cascode configuration instead if this does not yield the gain you are after. This may be helpful:
https://www.allaboutcircuits.com/textbook/semiconductors/chpt-4/cascode-amplifier/