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.

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Applications
Parameters
Settings
Bias Tee BOX
Previous versions
Article
Product details

Applications

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

version with PL SO-239 connectors

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

Settings

1. Current check point

- There is jumper as a short in the DC way to transistor. When you remove it, you are able to measure and set transistor bias current

2. Bias Current set

- This is 30 turn trimer. By this trimer you can set transistor bias current. Recommended around 40 to 50 mA @ 13.8 V

3. Variable ATT

- This is 30 turn trimer. It is connected at the output of preamplifier and works as a Variable Attenuator. You can set total gain from nill to around 18 dB

4. Input/Output protection

- There are Input and Output diode limiters. You can disconnect it by the jumpers. Just open in.
- These are hard clipping limiters but for high RF level

5. Power over coax

- This jumper must be shorted when you want to power amplifier over the coax cable - DC voltage applied by some Bias Tee

Bias Tee BOX

You can use Bias Tee BOX for power over coax

example with Bias Tee Box and Bi-Dir beverage

Previous versions

ℹ   Manual for previous versions: manual

Article

ℹ   Read article RX ANT Switching box on my BLOG.