The adjustments of the two additional compensating condensers [trimmers] in the police frequency band on the Model 81 is made at 1700 K.C. and 2400 K.C. These condensers are located on the under side of the chassis and are indicated as No. 8 and No. 9 in the diagrams of Philco Service Bulletin No. 154.
The condenser No. 8 is adjusted by setting the dial at approximately 1700 K.C. and adjusting for maximum volume on a police broadcast station [or your signal generator] at this frequency. The condenser No. 9 is adjusted in the same manner at 2400 K.C.
From the Philco Serviceman – May, 1933.