RX - Preamp module 2N5109

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This is very simply preamplifier module with 2N5109 transistor based on W7IUV design. You can use it as high IP preamplifier, buffer amplifier or small driver. Gain is up to 18dB and there is also build in variable ATT. You can easy set gain as high as you need! As well you can set right transistor bias with multi turn potentiometer. Two relays offer bypass switching if there is no power supply.


  • High IP RX preamplifier - RX antennas
  • Buffer amplifier
  • Driver amplifier



  • Supply voltage 12 to 15 V
  • Supply current up to 180 mA - include relays current

  • gain for 50 kHz to 1 MHz

  • gain for 1 MHz to 70 MHz

  • Input SWR, S11

Part List(Edit)

Part Value Device
ATT-TRIM R 200R R-TRIMM64W Multi turns Bourns 3296 W
C1 C 100nF C-EU050-024X044
C18 C 100nF C-EU050-024X044
C19 C 100nF C-EU050-024X044
C20 CPOL 10uF/25V CPOL-EUE2.5-5
C21 C 100nF C-EU050-024X044
C22 C 100nF C-EU050-024X044
C23 C 100nF C-EU050-024X044
C24 CPOL 10uF/25V CPOL-EUE2.5-5
C25 C 100nF C-EU050-024X044
C28 C 100nF C-EU050-024X044
C35 C 100nF C-EU050-024X044
D1 D 1N4148 DO35-7 N4148DO35-7
L1 T 5t FT50-75
L2 T 5t FT50-75
L3 FR3-FR TYPE FR type
R1 R 150 R-EU_0207/10
R4 R 2k R-TRIMM64W
R5 R 2k7 R-EU_0207/10
R6 R 680 R-EU_0207/10
R7 R 1k R-EU_0207/10
R8 R 6R8 R-EU_0207/10
R9 R 12R R-EU_0207/10
RE11 G5V-2 G5V-2
RE12 G5V-2 G5V-2
T1 TR 2N5109 Motorola
X1 Wago W237-102


KIT Assembling(Edit)

  • Insert two multi-turn trimmers
    • there is 2 kOhms (202) and 200 Ohm (201)
  • Insert resistors

  • continue with capacitors
    • small yellow 104 apacitors are 100 nF
    • continue with two blue electrolytic capacitor - PLEASE be careful on polarity!
    • minus (-) is marked on capacitor, plus (+) on PCB

  • Insert diode, relay and inductor
    • two Omron relays
    • Diode 1N4007 - please follow polarity on PCB
    • small inductor L3

  • Insert transistor to the radiator and wind output transformer
    • use screw driver to open radiator a little bit if needed.
    • there is small ferrite core T50-75
    • wind 5 turns of bifilar wires

  • Example of the binocular wires :)

  • please measure start and end of both windings
  • insert it into the PCB in the right order!


  • There is nothing to tune on RF side. It is wide band amplifier.
  • You only need to set right TRANSISTOR BIAS current and Gain.
    • disconnect jumper JP1
    • connect mA meter there (200 mA scale is fine)
    • connect supply voltage you want - from 12 to 15 V
    • turn the resistor trimmer R4 (BIAS) and set bias current you want - it should be from 60 to 85 mA - depends on application
    • than connect jumper short back again
  • With the resistor trimmer (ATT-TRIM) you can set amplifier gain as you need.
    • from 0 to about 18 dB
    • turn the ATT-TRIM (201)