2X4+ Superhet   crystal-filter frequency. Turn off the modulation of the generator signal, switch on S-2, and tune L-10 for a beat note. Setting the B.F.O. to one side or the other of the crystal-filter frequency should result in good single-signal C.W. reception, with little or no response on the "other side" of zero beat. If a borrowed receiver is used to align the receiver, use the borrowed receiver to set the 2 x 4 + B.F.O. on 1700 kc. and the high-frequency oscillator on 5.2 Mc. Then feed a 3.5-Mc. signal from a V.F.O. or exciter into the 2 x 4 + and peak L-8 and L-9 for loudest signal with the B.F.O. on. As with a signal generator, the signal should be kept at a low level, by reducing power or coupling to the V.F.O. or by detuning C-1. After the I.F. has been aligned roughly, the crystal-filter frequency can be found by minor tuning excursions, looking for a sudden peak in signal response. Most grid-dip oscillators have enough modulation on the signal so that the signal can be used in the same way as the output from a modulated signal generator. If the g.d.o. calibration can be trusted, the 2 x 4 H.F. oscillator can be set on 5.2 Mc. (and left) and a 3.5-Mc. g.d.o. signal introduced at the 2 x 4 input. Inductors L-8 and L-9 should then be peaked for maximum signal, after which S-2 can be closed and L10 brought to tune. If the g.d.o. tunes to 1700 kc., the I.F. can be aligned without regard for the setting of the H.F. oscillator. Once the I.F. and B.F.O. have been aligned, all that remains is proper setting of the H.F. oscillator range by the setting of C-3. When correctly set, the 3.5- to 4.0-Mc, band will tune roughly from 5 to 95 on the tuning dial (as will 6.9 to 7.4 Mc.). All that is necessary to go from one band to the other is to set C-1 in the maximum capacitance end (80 meters) or the low-capacitance end (40 meters). With an antenna having a coaxial feed line (for which the receiver is designed), the 80-and 40-meter resonance peaks will be quite sharp and the background noise will come up sharply at these points. If two peaks are found close together, adjustment of the 30-pf. trimmer across C-1A is indicated. When the receiver is working properly on 40 and 80 meters,

HIGH-FREQUENCY RECEIVERS S-1 can be closed and C-2 adjusted to bring in WWV (5 Mc.) at the center (or any preferred spot) of the tuning dial. C-1 should be set around half scale (noise peak) when receiving WWV. Since K-1 is mounted upside down, it may be necessary to reduce the spring tension slightly, to enable the relay to close. When the receiver is properly aligned and with no antenna connected, turning on the B.F.O. by closing S-2 should produce an increase in background noise in the output of the receiver. If this rushing noise is just barely audible, increase the capacitance at C-6 by moving the free end of the wire closer to Pin 2 of V-3A. With a v.t.v.m. the d.c. voltage to chassis at the output end of RFC-2 should go from about +30 to about +35 or +36 when S-2 is closed. To check operation of the H.F. oscillator, connect a voltmeter across the 3300-ohm resistor in the plate lead (- terminal to end connected to 0.01-mfd. capacitor). The voltage should jump from about 15 to 35 when the stator of C-3 or C-4 is momentarily shorted to chassis (use a screw-driver with an insulated handle to avoid a shock). If the oscillator doesn't work, it may be because the outside turns of L-6 and L-7 are not connected to plate and grid respectively. The crystal filter should give good rejection of the "other side of zero beat" in C.W. reception. If it doesn't, try dressing the 470-pf. and the 200-pf. capacitors across L-8 as close to the chassis as feasible, to minimize leakage around the crystal. The selectivity of the receiver is such that the reception of S.S.B.. phone signals is quite normal, but turning off the B.F.O., for the reception of A.M. phone signals, will result in a "boomy" sound to the signal. This is an inescapable result of the selectivity; it can be reduced by tuning slightly to one side or the other of the "center" of the A.M. signal. Best reception will be obtained when the regular transmitting antenna is used with the receiver.

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