How did 'presets' work on old radios - I'm talking OLD radios here, kids - pre-digital, manual tuning.

Question

Today's radios are easy to set presets for a particular station.

However, I've seen that even on very old radio sets (both home and car) that it's possible to assign your favorite station to a button, just like today.

It's obviously mechanical in nature...but does anyone know how it actually *works*?

Answer 1

Old analog radios were tuned by adjusting a variable capacitor to resonate with a fixed inductor. This variable capacitor would be connected to a dial cord (a string) which went through a reduction mechanism (think gear reduction) to provide precise tuning by the radio's tuning k**b.

The preset buttons (there were usually 5 on a radio) were just a pully device that would pull the dial cord to a preset length which in turn would move the capacitor to provide the correct amount of capacitance to resonate with the inductor at the desired frequency.

Answer 2

Or, in English,

(no offense, but I've been dealing with engineers for 40 years and they all talk like that - especially to jocks, PDs and salespeople ;<):

Behind the face plate, a string or wire would pull the tuner to the correct spot on the dial. You would generally set the buttons by setting the tuner to the station you wanted, then push the button hard and pull back half-way out. That would set it in place so it would return to that spot each time you pushed that button. Sometimes, you'd need a little "fine" tuning, as radios have a tendency to drift, especially in a mobile situation.

-a guy named duh