If perf board is all you got to work with, it's a good idea to also install shielding around vital circuits, like how tuner modules and other digital modules are, enclosed in a metal canister or box soldered to the ground of the circuit.
RFB
For MW frequencies, perf-board works OK if you keep the leads short.
For 13.5 MHz there might be problems but it can be done. The main thing to remember is keep the component leads as short as possible, keep the stages physically apart or shielded, and use bypass caps from power to gnd. at each stage. It is sometimes overlooked that the power and ground leads can function as signal leads, thus the need for bypass to prevent this.
I have perf-boarded circuits operating at 28 MHz and it can be done.
Neil
I was concerned with the same type of problem caused by my Ramsey FM 25B.
Recently a string of storms rolled through Kentucky bringing heavy rains and gusting winds. The wind was too much for my FM Dipole antenna which as fastened to the front porch with zip ties and bungie cords. Luckily the antenna and mast were not damaged, but until i could get the antenna mounted back into place i was using the whip antenna provided with kit from Ramsey. That is when i noticed distortion, after playing with the audio chain and not seeing any change it dawned on me that the whip antenna mounts right into the board next to ic chips.
Bad idea but easy to remedy.
I have a cabinet from a TH transmitter that stopped working a year and half ago that was just collecting dust. I pulled out the TH board and mounted the Ramsey FM 25B into the cabinet using the bottom of the plastic Ramsey box as an insulator then grounded the transmitter to the cabinet. All the holes lined up in the back to allow audio and power cables to enter the appropriate plugs. Problem solved. The coax runs out of the tx into a short mount holding the whip. It works for now until i can get the dipole back up. Most importantly no distortion.