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Genesis LPC5

LPC5 is a RX-TX control board and Low Pass filter suitable for QRP transmitters. Basically, it allows you to connect your Q5 transmitter and external receiver to a common antenna. The LPC5 is rated at 5W and the band pass filter covers 5 bands: 80m, 60m/40m, 30m nad 20m.

The control board provides RX-TX switching and control voltage for both receiver and transmitter. It will allow you to safely use your "main radio" receiver while transmitting with Q5.

Genesis LPC5

The LPC5 will take your enjoyment of homebrew QRP transmitting to the next level!

Genesis LPC5 Control and Low Pass filter board video

Genesis Q5 crystal controlled QRP transmitter video

LPC5 Schematic diagram

Click Picture to Enlarge


Resistor R1, R2, R4, R6 10K 4
R3,R8, R10 1K 3
R5 22K (47K) 1
R7,R9 4.7K 2
R11, R12 2.2K 2
Capacitor C12, C13, C17, C18, C19, C20, C22, C23 100nF (104) 8
C14, C15 10nF (103) 2
C16, C21 220uF (2) 2
C7, C8, C10A 330pF (331) 3
C5, C10B 56pF (560) 2
C4, C19A 220pF (221) 2
C9B 47pF (470) 1
C11A 680pF (681) 1
C11B, C1A 82pF (820) 2
C2, C3, C6 180pF (181) 3
Diode D1 - D9 1N4148 9
Trimmer TR1 100K (50K) 1
Relay K1, K2, K3 12V 1A 3
BNC Connector - 50Ω 3
Integral Circuit IC1 HEF 4069 1
Transistor T1, T2 BD140 2
RED - 1
Audio connector - 3.5m 3
PCB LPC5 - 1
Toroid T50-2 Red core 4
Wire Enamel 0.8mm 1m
Switch - SPDT 1

LPC5 Circuit Board

Genesis LPC5


Install nine 1N4148 diodes, D1-D9. Pay attention to band orientation!

Genesis LPC5

Install resistors R1-R12, electrolytic capacitor C21 and green and red LED diode.

Genesis LPC5

Again, pay attention to LED polarization!
Install as per photo below, flat side of LED housing is close to 2K2 resistor.
Genesis LPC5

Genesis LPC5

Install the following NPO capacitors:
100nf (104): C12, C13, C17, C18, C19, C20, C22, and C23.

10nF (103): C14, C15.

Electrolytic capacitor 220uF C16.

Vox delay trimmer TR1. Trimmer or variable potentiometer supplied may look different than one shown here.
(Note: AF amp trimmer TR2 is optional, not included in kit).

Genesis LPC5

Install IC1, T1, T2 and three 3.5mm audio connectors.
Pay attention to T1 and T2 orientation: align back side (heatsink side) with layout footprint line on PCB.

Genesis LPC5

Connect +12V and hand key. The green LED will be on (RX mode), When key-down (TX mode) the red LED will turn on. Adjust trimmer TR1 for delay.

Now install relay K3. Again, when pressing the key down (TX mode) the red LED will turn on and you will hear relay clicking. This completes assembly of RX/TX control.

Genesis LPC5

Install the following NPO capacitors

80m LP section:
C10A 330pF [331]
C10B 56pF [560]
C9A 220pF [221]
C9B 47pF [470]
C11A 680pF [681]
C11B 82pF [820]

40m LP:
C8 330pF [331]
C7 330pF [331]
C6 180pF [181]

30m LP:
C1A 82pF [820]
C1B 33pF [330]
C5 56pF [560]
C2 180pF [181]

20m LP:
C3 180pF [181]
C4 220pF [221]

Genesis LPC5

Wind four inductors L1-L4 as per photo using 0.8mm enamel wire on T50-2 core.

For toroid winding instruction see toroid winding tutorial

Genesis LPC5

Strip, form and tin coil leads as per photo

Genesis LPC5

Install the inductors L1-L4

Genesis LPC5

Install relays K1 and K2

Genesis LPC5

Finally, install the 3 BNC connectors.

Genesis LPC5

This completes the assembly of Genesis LPC5 control and LP filter board.

Genesis LPC5

73 and happy DXing! YU1LM and VK1AA


1. Position of variable potentiometer TR1 PCB mount

Genesis LPC5 Position of variable potentiometer TR1 PCB mount

2. Alternative RX/TX K3 relay wiring version 1

Genesis LPC5 Alternative RX/TX K3 relay wiring

Genesis LPC5 Alternative RX/TX K3 relay wiring

3. Alternative RX/TX K3 relay wiring version 2

Here is yet another alternative way of RX/TX switching.
In this case, on receive TX is connected to ground and during transmit, the RX input is grounded.

Choose the alternative most suitable for your desired configuration or the one with highest RX/TX signal separation.

Genesis LPC5 Alternative RX/TX K3 relay wiring

Genesis LPC5 Alternative RX/TX K3 relay wiring


Control board for Q5 RX/TX switching, TX delay and set of band pass filters for 80m, 40m, 30m and 20m. Includes professionally manufactured single layer PCB and all components. Online assembly help file. Yahoo Group support. Postage $9 air-mail, worldwide.

Delivery status: IN STOCK

Click here to place an order.

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US$ 39.95

Need help? email: info@GenesisRadio.com.au

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