**Hendricks QRP Kits**

BITX20A

Assembly Manual

*Step-By-Step Assembly*

October 2, 2007__Receiver AF Amplifier__[ ] C-36, 100 mfd Observe Polarity

[ ] C-83, 0.1 mfd

[ ] R-81, 10 ohms brn-blk-blk

[ ] C-82, 10 mfd Observe Polarity

[ ] IC-1, LM386,

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] C86, 100 mfd Observe Polarity

[ ] R-82, 10 ohms brn-blk-blk

[ ] R-79, 220 ohms red-red-brn

[ ] R-80, 10K ohms brn-blk-org NOTE: Off-board component. Use 6 inch leads.

Gnd lead near C-82, Hot lead near Q-16.

[ ] C-81, 10 mfd Observe Polarity

[ ] C-80, 100 mfd Observe Polarity

[ ] R-78, 4.7K ohms yel-vio-red

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] Q-16, 2N3904

[ ] Q-25, 2N3904

[ ] R-88, 4.7K ohms yel-vio-red

[ ] R-89, 22K ohms (red-red-orange)

[ ] C-47, 0 pf (This is an artefact from an older PCB design. Do not install any capacitor here.)

[ ] C-79, 0.022 mfd

[ ] R-77, 3.3K ohms org-org-red

[ ] C-8, 10 mfd Observe Polarity

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] Speaker or Headphone Jack Connection. Use 6 inch leads.

Ground is pad near C-75.

[ ] D-18, SB320 Diode Observe Polarity

[ ] C-87, 0.1 mfd

[ ] C-74, 100 mfd Observe Polarity

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

__Transmittter AF Amplifier__

[ ] R-76, 10 ohms brn-blk-blk

[ ] R-92, 4.7K ohms yel-vio-red NOTE: This is power for FET mike. Omit for dynamic or crystal mike.

[ ] C-60, 10 mfd Observe Polarity

[ ] C-76, 0.01 mfd

[ ] R-73, 2.7K ohms red-vio-red

[ ] R-72, 10K ohms brn-blk-org

[ ] R-75, 1K ohms brn-blk-red

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] Q-15, 2N3904

[ ] R-74, 100 ohms brn-blk-brn

[ ] C-73, 100 mfd Observe Polarity

[ ] R-93, 220 ohms red-red-brn

[ ] C-77, 10 mfd Observe Polarity

[ ] C-75, 100 mfd Observe Polarity

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

__BFO Mixer Assembly__

[ ] T-6, 8:8:8 turns #28 tirfilar on FT37-43 (black) core. This is three wires, each 6 inches long.

[ ] C-66, 15 pf

[ ] C-65, 30 pf variable capacitor. Note: flat side is RF side, round side is ground.

[ ] R-66, 200 ohms PCB type potentiometer

[ ] R-65, 220 ohms (red-red-brn)

[ ] R-63, 22 ohms (red-red-blk)

[ ] R-64, 220 ohms (red-red-brn)

**NOTE****:** Pay particular attention to the location and values of R-63, R-64, and R-65.

If you get these in the wrong places your receiver sensitivity and transmitter

power output may be degraded. Swapping the 22 ohm resistor with one of

the 220 ohm resistors is a common mistake in early BITX20 units and

possibly in BITX20A kits.

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

__BFO & Carrier Oscillator__

[ ] C-88, 33 pf NOTE: May not be needed, but provided to insure adequate tuning range.

[ ] C-72, 30 pf variable capacitor, Note: flat side is RF side, round side is ground.

[ ] L-5, 8.2 uh molded inductor

[ ] X-5, 11.0 MHz Crystal

[ ] C-68, 220 pf

[ ] C-69, 220 pf

[ ] R-70, 150K ohms brn-grn-yel

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] Q-14, 2N3904

[ ] R-71, 1K ohms brn-blk-red

[ ] C-70, 100 mfd Observe Polarity

[ ] R-69, 100 ohms brn-blk-brn

[ ] R-68, 1K ohms brn-blk-red

[ ] Q-13, 2N3904

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] C-67, 0.1 mfd

[ ] C-71, 0.1 mfd

[ ] R-67, 1K ohms brn-blk-red

[ ] D-14, 1N4148 Observe Polarity

[ ] D-15, 1N4148 Observe Polarity

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

__Receive 2nd IF Amp and Transmit 1st IF Amp__

[ ] C-64, 0.1 mfd

[ ] R-58, 1K ohms brn-blk-red

[ ] R-57, 2.2K ohms red-red-red

[ ] Q-12, 2N3904

[ ] R-60, 4.7 ohms yel-vio-gld

[ ] C-61, 0.1 mfd

[ ] R-59, 470 ohms yel-vio-brn

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] D-13, 1N4148 Observe Polarity

[ ] R-61, 220 ohms red-red-brn

[ ] C-63, 0.1 mfd

[ ] R-62, 100 ohms brn-blk-brn

[ ] R-56, 100 ohms brn-blk-brn

[ ] C-57, 0.1 mfd

[ ] D-12, 1N4148 Observe Polarity

[ ] Q-17, 2N3904

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] C-58, 0.1 mfd

[ ] R-53, 470 ohms

[ ] R-55, 4.7K ohms yel-vio-red

[ ] R-52, 1K ohms brn-blk-red

[ ] Q-11, 2N3904

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] R-54, 4.7K ohms yel-vio-red

[ ] C-59, 0.1 mfd

[ ] R-51, 220 ohms red-red-brn

[ ] C-89, 100 pf

[ ] C-62, 100 pf

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

__Receive and Transmit Changeover Relay__

[ ] D-17, 1N4004 diode Observe Polarity

[ ] K1, 351 Relay

[ ] Connect push-to-talk part of microphone connector, or a temporary momentary switch as PTT.

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

__Crystal Filter__

[ ] C-56, 82 pf

[ ] C-55, 100 pf

[ ] C-54, 82 pf

[ ] X-1, 11.0 MHz Add ground wire soldered to crystal case

[ ] X-2, 11.0 MHz Add ground wire soldered to crystal case

[ ] X-3, 11.0 MHz Add ground wire soldered to crystal case

[ ] X-4, 11.0 MHz Add ground wire soldered to crystal case

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

__Receiver 1st IF and Transmitter 2nd IF__

[ ] C-53, 100 pf

[ ] R-46, 1K ohms brn-blk-red

[ ] R-45, 2.2K ohms red-red-red

[ ] Q-10, 2N3904

[ ] R-48, 10 ohms brn-blk-blk

[ ] C-44, 0.1 mfd

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] R-47, 220 ohms red-red-brn

[ ] D-11, 1N4148 Observe Polarity

R-49, 220 ohms red-red-brn

[ ] C-45, 0.1 mfd

[ ] C-46, 0.1 mfd

[ ] R-50, 100 ohms brn-blk-brn

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] C-52, 100 pf

[ ] D-10, 1N4148 Observe Polarity

[ ] R-43, 220 ohms red-red-brn

[ ] C-42, 0.1 mfd

[ ] R-44, 100 ohms brn-blk-brn

[ ] Q-9, 2N3904

[ ] R-39, 2.2K ohms red-red-red

[ ] C-43, 0.1 mfd

[ ] R-40, 1K ohms brn-blk-red

[ ] R-41, 220 ohms red-red-brn

[ ] R-42, 10 ohms brn-blk-blk

[ ] C-40, 0.1 mfd

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

__1st Mixer__

[ ] T-4, 8:8:8 turns trifilar, 6 inches per #26 on FT37-43 (black) core. Twist to 8 twists per inch

[ ] T-5, 8:8:8 turns trifilar, 6 inches per #26 of FT37-43 (black) core. Twist to 8 twists per inch

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] D-4, 1N4148 Observe Polarity

[ ] D-5, 1N4148 Observe Polarity

[ ] D-6, 1N4148 Observe Polarity

[ ] D-7, 1N4148 Observe Polarity

[ ] R-26, 100 ohms brn-blk-brn

[ ] C-30, 0.1 mfd

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

__VFO__

[ ] R-35, 100 ohms brn-blk-brn

[ ] D-8, 1N4739A, 9.1 Volt Zener Observe Polarity

[ ] R-33, 10K ohms brn-blk-org

[ ] R-34, 10K ohms brn-blk-org

[ ] C-33, 0.1 mfd

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] Q-8, 2N3904

[ ] Q-7, 2N3904

[ ] Q-6, 2N3904

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] R-31, 1K ohms brn-blk-red

[ ] C-32, 0.1 mfd

[ ] R-28, 1K ohms brn-blk-red

[ ] R-27, 1K ohms brn-blk-red

[ ] R-30, 10 ohms brn-blk-blk

[ ] R-29, 100 ohms brn-blk-brn

[ ] C-31, 0.1 mfd

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] R-36, 2.2K ohms red-red-red

[ ] C-90, 33 pf

[ ] C-35, 470 pf Polystyrene

[ ] C-34, 470 pf Polystyrene

[ ] C-15, 180 pf

[ ] C-37, 220 pf Polystyrene

[ ] C-39, 33 pf

[ ] R-32, 4700 ohms yel-vio-red

[ ] C-91, 56 pf

[ ] D-9, 1N4752A, 33 Volt Zener (used as fine tuning varicap) Observe Polarity

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] R-38, 150K ohms brn-grn-yel

[ ] L-7, 50 turns #36 on T-37-6 (yellow) core

[ ] C-38, 160 pf Variable Capacitor. Polyvaricon used as main tuning. See diagram for which leads to use.

[ ] R-37, 10K Potentiometer. This is the fine tuning adjustment.

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

__Receive and Transmit RF Amplifiers__

[ ] C-27, 0.1 mfd

[ ] C-29, 0.1 mfd

[ ] R-20, 2.2K ohms red-red-red

[ ] R-21, 1K ohms brn-blk-red

[ ] R-23, 10 ohms brn-blk-blk

[ ] R-22, 220 ohms red-red-brn

[ ] C-26, 0.1 mfd

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] Q-5, 2N3904

[ ] D-3, 1N4148 Observe Polarity

[ ] R-24, 220 ohms red-red-brn

[ ] R-25, 100 ohms brn-blk-brn

[ ] C-28, 0.1 mfd

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] D-2, 1N4148 Observe Polarity

[ ] R-18, 220 ohms red-red-brn

[ ] C-23, 0.1 mfd

[ ] R-19, 100 ohms brn-blk-brn

[ ] R-16, 220 ohms red-red-brn

[ ] R-17, 10 ohms brn-blk-blk

[ ] C-21, 0.1 mfd

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] R-14, 2.2K ohms red-red-brn

[ ] Q-4, 2N3904

[ ] R-15, 1K ohms brn-blk-red

[ ] L-10, 1.2 uh molded inductor

[ ] C-25, 100 pf

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

__Receive and Transmit Front End Filter__

[ ] C-24, 8.2 pf

[ ] L-6, 18 turns (20 inches) #26 on T-37-6 (yellow) core

[ ] C-18, 30 pf NOTE: The rounded side connects to ground and the flat side to RF

[ ] C-20, 82 pf

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] C-19, 10 pf

[ ] C-17, 56 pf

[ ] C-16, 10 pf

[ ] L-4, 18 turns (20 inches) #26 on T-37-6 (yellow) core

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] C-14, 30 pf NOTE: The rounded side connects to ground and the flat side to RF

[ ] C-13, 82 pf

[ ] C-11, 10 pf

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

__T:R Switches__

[ ] Q-23, 2N7000

[ ] R-86, 4.7K ohms yel-vio-red

[ ] R-87, 4.7K ohms yel-vio-red

[ ] Q-24, 2N7000

[ ] Q-26, 2N7000

[ ] R-94, 4.7K ohms yel-vio-red

[ ] C-41, 0.1 mfd

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] R-85, 4.7K ohms yel-vio-red

[ ] Q-22, 2N7000

[ ] R-84, 4.7K ohms yel-vio-red

[ ] Q-21, FQN1N50C FET

[ ] C-50, 0.1 mfd

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

__Antenna Filter__

[ ] C-47A, 100 pf

[ ] C-47B, 100 pf

[ ] L-2, 14 turns #26 (10 inches) on T-37-6 (yellow) core

[ ] C-48A, 180 pf

[ ] C-48B, 180 pf

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] L-1, 12 turns (8 inches) #26 on T37-6 (yellow) core __ __**NOTE:** L1 is 14 turns for kits 1 thru 100, and 12 turns for kits above number 100.

[ ] C-92, 68 pf ** ****NOTE: ** C-92 is not provided on kits 1 thru 100, and is provided in kits above number 100.

* *__The provision of C-92 and reducing L1 from 14 to 12 turns is a late change that provided__

__additional harmonic reduction.__

[ ] C-49B, 100 pf

[ ] C-49A, 100 pf

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

__RF PA Drivers__

[ ] R-90, 100 ohms brn-blk-brn

[ ] C-9, 0.1 mfd

[ ] Q-20, 2N5486

[ ] R-83, 200 ohm variable NOTE: Turn fully CCW (Counter Clock-Wise)

[ ] C-10, 0.1 mfd

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] R-9, 2.2K ohms red-red-red

[ ] R-10, 1K ohms brn-blk-red

[ ] Q-3, 2N3904

[ ] R-12, 10 ohms brn-blk-blk

[ ] C-12, 0.1 mfd

[ ] R-11, 100 ohms brn-blk-brn

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] R-13, 22 ohms red-red-blk

[ ] C-6, 0.1 mfd

[ ] T-3, 8:8 turns (6 inches) bifilar on #26 on FT37-43, (black) core. Twist to 8 turns per inch

[ ] R-5, 2.2K ohms red-red-red

[ ] R-6, 2.2K ohms red-red-red

[ ] C-4, 0.1 mfd

[ ] T-8, 10K potentiometer NOTE: Turn fully CCW

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] Q-18, BS170 MOSFET

[ ] Q-19, BS170 MOSFET

[ ] R-7, 2.2 ohms red-red-gld

[ ] C-7, 0.1 mfd

[ ] T-2, 8:8:8 turns (6 inches) trifilar #26 on FT37-43 (black) core. Twist to 8 turns per inch

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

__RF PA Stage__

[ ] C-51, 0.1 mfd

[ ] R-91, 10K potentiometer NOTE: Turn fully CCW

[ ] R-2, 10K potentiometer NOTE: Turn fully CCW

[ ] C-5, 0.1 mfd

[ ] C-22, 0.1 mfd

[ ] R-4, 2.2K ohms red-red-red

[ ] R-1, 2.2K ohms red-red-red

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] C-1, 0.1 mfd

[ ] C-2, 0.1 mfd

[ ] C-3, 0.1 mfd

[ ] D-1, 1N4734A 5.6 Volt Zener Observe Polarity

[ ] R-3, 1K ohms brn-blk-red

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

[ ] L-3, 8 turns (6 inches) #26 on FT37-43 (black) core

[ ] L-9, 8 turns (6 inches) #26 on FT37-43 (black) core

[ ] T-1, Primary = 6 turns, Secondary = 8 turns #26 on FT37-43 (black) core

[ ] Q-1, IRF510 MOSFET Bolt to heatsink, then install

[ ] Q-2, IRF510 MOSFET Bolt to heatsink, then install

[ ] Solder

[ ] Clip Excess Lead Length

[ ] Inspect Solder Connections

====================================