Antenna Trimming
I'd suggest not fiddling with this adjustment but if you simply have to , be aware you cannot do it with as ferrous metal tool ~ brass or plastic only .
On older radios the adjuster will always be on the outside , usually a tiny hex headed sticking out , sometimes a flat headed screw with a thin slot , never a cross head .
You warm up the radio then tune in a weak station on the lower 1/2 of the dial and s l o w l y turn the adjuster a *tiny* bit ~ 1/4 turn means you've prolly ruined it so go easy here ! .
Most of the time , polishing the antenna mast , antenna lead plug and adding ground wires from radio to cab , will make it work much better than it did .