Atlas 210x User Manual

4-11. PC-100C - FIRST MIXER/FIRST I.F. AMPLIFIER
In the receive mode, the R.F. signal is coupled from terminal 1 of PC-100C to the primary of the trifllar toroid
transformer LI 01, through capacitors C101 and C110, to the double balanced diode ring mixer, D101 through
D104. The VFO oscillator signal is coupled through R105 — C109 to the center tap of the secondary windings of
L101, then through C101 and C110 to the First Mixer. The two signals are heterodyned and the difference
frequency is the 5520 kHz I.F. signal. The output of the First Mixer is coupled through the trifllar toroid
transformer L102, through a tuned circuit consisting of C104 through Cl 07 and LI 03, to the base of the First I.F.
Amplifier Q101. The tuned circuit is tuned to the L.F. frequency of 5520 kHz. The signal is amplified by Q101
and then connected through terminal 13 of PC-100C to the crystal ladder filter, which then goes to terminal 3 at
PC-200C.
In the transmit mode, the transmit audio input is coupled from terminal 7 of PC-100C through LI 04 to the First
Mixer, which now operates as a balanced modulator. The carrier oscillator injection is through terminal 4 of PC-
100C and is coupled to the balanced modulator through R105, C109, C110, and C101. The output of the balanced
modulator (D101 through D104) is a double sideband, suppressed carrier signal. R101 is used to balance out the
carrier, and C103 is used for phase balance. The double sideband signal is at the I.F. frequency of 5520 kHz, and
is tuned by the tuned circuit consisting of C104 through C107 and L103. Q101 is the Transmit I.F. Amplifier, and
its output is coupled to the Crystal Ladder Filter in the same manner as in the receive mode.
Diode D105 is used to short the receiver input circuit in transmit mode, thus preventing stray transmitter energy
from entering the mixer circuit. Diodes D106, 107 and 108 permit R.F. Gain control of Q101 during Receive
mode, while maintaining fixed gain in Transmit mode. RL101 switches the +13 volt line for Transmit mode, and
also switches the meter circuit from receive to transmit function.
One of the primary advantages of the double balanced diode ring mixer is that both signal and oscillator injection
frequencies are essentially balanced out and do not appear in the output circuit. Only the sum and difference
frequencies are present at the output. Also, the oscillator is balanced out from the antenna input terminal,
eliminating the risk of oscillator radiation.
PC-100C CIRCUIT COMPONENTS
First Mixer, First I.F. Amp
C101,108,109,110,112
. . . . .01 MF 100VDisc R101 ...... . . . Car. Bal. Trim Pot. 100 Ohms
C102 .............. ....... 22pF10% Disc R102....... ............ 10K 10% 1/4Watt
C 103 Car. Phase Bal.. . . . . . 10-80 pF Trimmer R103,110. .. ........... 4.7K 10% 1/4Watt
C104,107 .......... . . . . .001 MF 20% Disc R104 ...... ............ 330 10% 1/4Watt
C105 .............. . . . . . 100 pF 10% Disc R105 ...... ............. 47 10% '/4Watt
C106 .............. ....... 91 pF 5% Disc R106,107 ... ............. 1K 10% 1/4Watt
C111 .............. ..... 0.1 MF 50V Disc R108 ...... ............ 180 10% 1/4Watt
C113 .............. 15 MF 20V Electrolytic R109 ...... ............ 820 10% 1/4Watt
D101,102,103, RL101...... ............ 3p2t 12 vdc Relay
104,107,108 . . . . 1 N4148 Silicon Diode L101.102. .. ......... Trifilar Toroid XFMR
D105,106 .......... . . BA-182 Silicon Diode L103 ...... ............. Shielded I.F. Coil
Q101 .............. . . 2N3866 1st I.F. Amp. L104,105 . ................ 200 uH RFC
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Atlas 210x Specifications

General

Brand	Atlas
Model	210x
Category	Transceiver
Language	English