Minuteman missile silos used an interesting hardened UHF antenna. What kind of antenna is this? Does anyone have a drawing with a cross section?
Jay Moore added a picture to a different type of hardened antenna, the truncated cone in the foreground. Jay's antenna might be an annular slot antenna, if it is an antenna and not another hatch. In that case, the lighter gray circle would be a dielectric. I don't think these are the same antenna types.