Back when I was a really keen radio amateur, a group I was involved with were setting up a UHF repeater on Edge Hill near Banbury (GB3EH). The equipment was housed in a large metal cabinet mounted high up on the wall in a large barn on a farm in a position that had excellent RF takeoff in all directions. The antenna cables were passed through the wall to the transmit and receive antennas mounted on a pole attached to the barn wall.
As it was an unattended installation, and it could get very cold up there in winter, a 60W incandescent lamp was installed in the cabinet on a thermostat. Excellent use of a simple light bulb..! I had a photograph somewhere, if I still have it (and can find it) I'll post it
Edit: The repeater is now much modified from its original installation and looking at the photos on the website for it
here it doesn't appear to have a light bulb in it any more