SA612AN PDF Spec Sheet
This HF Mixer kit includes VXO circuit parts to be used with the 612 audio detector to receive 40 meter signals on 7030 KHz.
The balanced front end of the 612 mixer connects to a BN-43-2402 balun transformer for matching.
For a 50 ohm input, make the primary 2 turns and the secondary 12 turns center tapped at 6 turns. Use the 34 GA wire included in the kit.
The center tap is the mixer AGC control. See the LM386 amp kit for more info.
D1,D2 are input protection diodes; not required and not included in the kit.
L1 is used to lower the mixer's crystal freq. Using 14 turns of 27 GA wire on the black FT37-61 core will provide a tuning range of about 7022 to 7031 KHz.
More than 14 turns tend to stop the VXO from oscillating.
OUTPUT: Parts are included in the PCB bag for 3 different output circuits.
1. Single ended output; connect the 1000pF cap from pin5 of U1 to pin2 of J3
2. Balanced broadband; wind a 10turn:2turn binocular transformer using the 34 GA wire and connect the 10 turns across pins 4 and 5 of U1. Connect the 2 turns to pin2 of J3 and ground.
3. Balanced tuned; Install C5 (note flat side physical polarity) and C6.
For 7030 KHz output, wind a 24 turn primary and a 5 turn secondary on a red T37-2 toroid and install on the PCB. Use the 27 GA wire (red & green)
Note: The 34 GA wire is heat stripable while the 27 GA wire is not.
Parts List
T1 - BN-43-2402 - 1 foot 34 GA
L1 - FT37-61 - 1 foot 27 GA red
OUTPUT OPTIONS:
Tuned balanced: L2 - T37-2 - 14 inches 27 GA red & 4 inches 27 GA green
Broadband balanced: L2 - BN-43-2402 - 1 foot 34 GA
Single ended: C9 - 1000p labeled "102" (not shown on PCB)
C1,C2 - 330 n
C3 - 100p
C4 - 56p
C5 - 70p
C6 - 150p
C7,C8 - 47n (labeled 473)
R1 - 100
R2 - 100k
D3 - MV209
U1 - SA612AN