Atlas 210x, Installation, Operation And Maintenance Manual

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4-13. PC-300C Receiver Audio, Oscillator Switch
The audio output from PC-200C is coupled through terminal 20 of PC-300C, through C303 to pin 12 of the Integrated Circuit
Q301, which is the A.F. Amplifier. The output of Q301 is coupled through C302 to terminal 22 of PC-300C to the AF GAIN
control on the front panel, then back through terminal 12 of PC-300C to the input of the AF Power Amplifier Q302. The
signal is further amplified and coupled through C320 to terminal 15 of PC-300C to the speaker. Q302 delivers 2 watts of
audio to the 3.2 ohm speaker.
The output of Q301 is also coupled through C309 to D301 and D302, the AGC rectifiers. AGC is then coupled through L301
to the input of Q301B which is the AGC Amplifier. The AGC output is fed from pin 7 of Q301B through terminal 17 of PC-
300C to terminal 19 of PC-200C where it is coupled through R202 to the Second I.F. Amplifier. AGC attack and decay time
are controlled by C310, R312, and R311.
ALC voltage from the SWR bridge is coupled through D303 to Q301B, controlling I.F. gain similar to AGC in receive mode.
This same circuit also carries the high SWR, or infinite SWR protection system. High values of reflected voltage from the
SWR bridge will reduce I.F. gain, resulting in reduced transmitter drive. SWR figure of 6 or more will practically cutoff the
transmitter drive through this circuit.
Q303, 304, 305 and 306 are the F.E.T. Oscillator switches, which connect the VFO and Carrier Oscillator (BFO) to the two
mixer stages in proper relationship for receive and transmit functions. The switching is controlled by the "T" line on terminal
1, which is grounded in receive mode and goes +13 in transmit mode.
PC-300C CIRCUIT COMPONENTS
Receiver Audio, Oscillator Switch
C301,304,307,308,314, L301 .....................………………………... 33uHRFC
323,324,325,326. ..…………………... .01 100V Disc
R301.307.313 ........………………. 5.6K 10% '/4 Watt
C302,317. ..............………………… .1 MF 50V Disc
R302 ................…………………... 27K 10% 1/4 Watt
C303 .................. ………………….22 MF 100V Disc
R303.310,311,324,
C305. ..........……………….. 47 MF 6.3V Electrolytic
321,327,328 .......…………………… 1K 10% '/4 Watt
C306.319. .......……………... 15 MF 20V Electrolytic
R305,315,316 ........………………... 470 10% '/4 Watt
C309.310.321. ....…………. 2.2 MF 50V Electrolytic
R306.314 ...........…………………. 100K 10% '/. Watt
C311,315. ........……………. 47 MF 16V Electrolytic
R308 ...............………………….... 1.5K 10% '/4 Watt
C312. ..........………………. 6.8 MF 35V Electrolytic
R309,317,318. ........……………... 2.2K 10% 1/4 Watt
C313 ............………………. 75 MF 15V Electrolytic
R312 ...............……………………... 1M 10% '/4Watt
C318 ...........……………….. 22 MF 16V Electrolytic
R319,320,322,323,325,326. ……..6.8K 10% 1/4 Watt
C320 ...........……………… 250 MF 20V Electrolytic
Q301A .............………………….. CA3086 A.F. Amp.
C322 ...............…………………. 47 MF 100V Mylar
Q301B. .............………………… CA3086 AGC Amp.
C327 ................…………………... 5-30 pF Trimmer
Q302. ............…………………. LM380N A.F. Output
0301,302,303, 0303,304,
304,305,306 ...………………. 1N4148 Silicon Diode
305,306 . 2N3819 FET Oscillator Switch
D307.308 .........……………... BA-182 Silicon Diode
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