[Milsurplus] ARC 27

[CL in NC]

Used to work on these almost 50 years ago now.  That Hubbard is a combination inductor and capacitor.  A common circular contact was on the ceramic frame on one end,  on one end, the bar had a 2 sided contact that rode this, just sliding along, and the circular contact added or subtracted to the overall inductance.  Integral to the whole thing was a rotor and stator for a capacitor, one rotor blade was sliced into quadrants, and had each quadrant edges  painted with a different color.  As you tuned the ARC27 across is range, you monitored the output of the spectrum generator and you would bend the rotor blades in and out from from the stator to peak the circuit as the bars length 'changed' as it got longer or shorter when the circular contact was adding or subtracting to the total depending on its position.  Each particular segment within 225 to 400MC had a different colored capacitor blade to 'tune', and the procedure was actually called 'blade tuning'.

Many commercial radios have their tune caps with slots on the outermost blades, but I have only seen one or two where alignment tells you to bend these in or out to optimize tracking or gain.

Charlie, W4MEC in  NC