How to assemble a receiver / transmitter for a spacecraft?

Question

Antenna

The bottom line is, you need to assemble the receiver and transmitter over a huge distance (> 100 km) of the UHF band, on the ground the receiver \ transmitter of unlimited sizes, on the device the dimensions are very limited (should fit on a cubesat).
I would be grateful if someone helps me collect and explain or find articles with all the calculations and step-by-step assembly.
I will not mind getting ready-made solutions, but still the goal is to collect