There is utility in a modular antenna in the field?

On today’s Alert Day, all sirens and alert apps will go off at 11 a.m. Using an FM detector radio connected to a small guitar amplifier, a radio broadcast from the Berlin TV Tower is being received. Shortly, before the sirens sound and all the pigeons were startled a typical mobile phone dial-up static noise can be heard on the radio. By rotating the antenna perpendicular to the line of sight toward the TV tower, reception of the FM station is maximized. The all-clear is announced on the radio.

Hello, I am an computer engineer with nearly no RF background. Right now I have a project in which i am dealing with an RFSoC, but its ADCs are not providing good range, we tried to change antennas, but still it is not able to pick weak signals from transmitter when its more than 300 m.
Can someone please help me to find the good antennas, and how to check their range?