Reference: NAVSHIPS 91875(A), para 2c(3)
Refer to figure 7-14. The output from the antenna preamplifier V501 is applied across the primary winding of one of the transformers T526 through T530 by the setting of a portion of S526, controlled by the band selector, through J501K and L, and J526B and C. The r-f section of the ganged tuning capacitor, C651C, is shunted across the secondary of the selected transformer to adjust the tuning of the transformer to the desired frequency. Fixed capacitors and a trimmer, together with the r-f tuning capacitor, resonate with the secondary coils to provide continuous tuning over the selected band. R-f voltages are taken off the appropriate transformer secondary through a portion of S526A and tube V526. Switch S526B shorts out certain unused primaries and secondaries of the transformers, to prevent absorption of the signal on the band in use. Coils and trimmers can be adjusted by means of a screwdriver at points shown in figures 7-8 and 7-9c.
Signals are amplified in V526 and applied to the mixer stage V551, through J526K and L and J551B and C. The r-f section of the gain control, R651A, (see figure 7-14, sheet 2) is in series with the cathode (pin 2) of V526 to vary the bias and control the gain. As was described previously, this control also adjusts the gain of the antenna preamplifier, V501. An automatic gain control voltage is applied to the circuit of the control grid (pin 1) of V526 through J526D when the reception control is set for A3 and F1 reception. See paragraph 2b(5) for a discussion of the AGC system.