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RX Preamp BOX manual

This is very simply preamplifier BOX with 2N5109 transistor based on W7IUV design. You can use it as high IP preamplifier for RX antennas (beverage, DHDL, flag etc). Gain is up to 18dB and there is also build in variable ATT. You can easy set the 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 voltage. You can use external power supply connected to the box or the bias tee box for power over the coax.



Jump to

Applications
Parameters
Schematic
PCB
Settings
Power over Coax cable
KIT Assembling
Part list
Transformers
Bias Tee BOX
Article



Applications

- High IP RX preamplifier - RX antennas
- Buffer amplifier

- Driver amplifier



version with PL SO-239 connectors

rx preamp box pl so-239 qro.cz hamparts.shop



version with F connectors

rx preamp box f qro.cz hamparts.shop




Parameters

- Supply voltage 12 to 14 V HIGHER SUPPLY VOLTAGE NEEDS COOLING AND RESISTORS TO RELAYS
- Supply current up to 180 mA - include relays current

rx preamplifier by qro.cz hamparts.shop



rx preamplifier by qro.cz hamparts.shop




Schematic

schematic rx preamp box v0.2 qro.cz hamparts.shop


PCB

pcb rx preamp box v0.2 qro.cz hamparts.shop


Settings

Variable Attenuator and RF protections

from 0 to about 18 dB
turn the ATT-TRIM (201)

rx preamp box rf protection qro.cz hamparts.shop

Transistor Bias current:

disconnect jumper JP1
connect mA meter there (200 mA scale is fina)
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

rx preamp box transistor bias current qro.cz hamparts.shop


Power over coax cable

Short jumper to enable power preamp over coax - with DC voltage.
If you use external power supply to internal DC connector, PLEASE DISCONNECT jumper JP4 - Coax PS

rx preamp box power over coax cable qro.cz hamparts.shop



KIT Assembling

version with PL SO-239 connectors

rx preamp box pl so-239 kit qro.cz hamparts.shop



version with F connectors

rx preamp box f kit qro.cz hamparts.shop



pcb after assembling all the parts

rx preamp box assembled pcb qro.cz hamparts.shop




Part list

NAMEPARTVALUE
GL1, GL2 neon lamp lamp 65V AC
D1 - D9 diode 1N4007
C1 - C5, C18 - C19, C21 - C23, C25, C28, C35 capacitor 100nF 100V
C20, C24 capacitor 10uF to 100uF
PTC PTC fuse THT 100mA
R1 resistor THT 150R
R5 resistor THT 2K7
R6 resistor THT 680R
R7 resistor THT 1K
R8 resistor THT 6R8
R9 resistor THT 12R
T1 heatsink heatsink TO39
T1 transistor 2N5109
RE11, RE12 relay G5V-12
ATT trimmer 200Ohm
R4 trimmer 2KOhm
L1, L2 ferrite core FT50-75
L3 inductor radial
L4 inductor 100uH
Wire wire 0.45 mm wire
X1 wago 2-pole wago
CON connectors PL SO-239 or F



Transformers

- There is one FT50-75 ferrite core
- Ferrite has got 5 turns of bifilar winding

- Clean coating from the ends. Place wires in right order like on the pictures
- Check it again :)

transformer core

transformer core

Cut/fold wires in half

transformer core cu wire



Make bifilar winding - you can use small PVC tube and ACU drill

transformer core cu wire

transformer core cu wire

transformer core cu wire

transformer core cu wire




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



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

Bias Tee BOX

You can use Bias Tee BOX for power over coax

rx preamp box with bias tee qro.cz hamparts.shop


Article

  Read article RX ANT Switching box on my BLOG.

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A bias tee is used to insert DC power into an HF signal to power remote antenna amplifiers or other devices.
A bias tee is used to insert DC power into an HF signal to power remote antenna amplifiers or other devices.
A bias tee is used to insert AC or DC power into an HF signal to power remote antenna preamplifiers (DC), Bi-directional beverages (AC) or other devices.
A bias tee is used to insert AC or DC power into an HF signal to power remote antenna preamplifiers (DC), Bi-directional beverages (AC) or other devices.
A bias tee is used to insert AC or DC power into an HF signal to power remote antenna preamplifiers (DC), Bi-directional beverages (AC) or other devices.
A bias tee is used to insert DC power into an HF signal to power remote antenna amplifiers or other devices.
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