EXTRA-6 50 MHz Contest Preamplifier

By Gyula Nagy, HA8ET 

 

 

Introduction

 

 

The EXTRA-6 50 MHz Contest Preamplifier has been developed based on the experiences with EXTRA-2 REV6 144 MHz Contest Preamplifier. During the simulations and optimizations I achieved that the preamp can be well applied for DX, EME and Contest purposes, as well.

 

The very high amplification, similarly to the 2 m version, makes it possible to adjust the GAIN. You have to adjust the GAIN not to overload the stages of the transverter or the transceiver.

 

The preamplifier can be fed through a condensator or a coaxial cable. The +12V supply voltage is needed for the preamp only in RX period.

 

Technical data:

Frequency range:…..……  49,5 MHz….51,9 MHz

Input/Output impedance:  50 Ω

Gain:………….………… 16 - 23 dB (adjustable)

Noise Figure………..……<0,6 dB (typ. 0,5)

S11:…………………….. -4,38 dB @ 50 MHz

S22:……………………..-20,9 dB @ 50 MHz

3dB Bandwidth:………..  2,39 MHz

10dB Bandwidth:………..  4,25 MHz

IP3………….……………>24 dBm

Broadcast rejection:……..>73 dB @ 100 MHz

Unconditionally stable

Moderate sensitivity to ESD

Supply voltage:……...…  +12…15V/152mA

Powered through antenna feed line, or separately

+40 dBm IP3 GaAs FET (ATF-53189)

Connectors:…………...... BNC or N 

Dimensions (Box):…….. 74 x 37 x 30 mm

 

Features

 

  1. Omitting parallel feedback (noise figure decreased, gain increased)
  2. Adjustable output attenuator to select an appropriate level of gain
  3. Applying a special source degeneration method (unconditional stability)
  4. Modified input matching circuit (lower noise figure, applicable also for EME)
  5. Improved drain and gate decoupling circuits (higher OIP3)
  6. Modified gate bias circuit (more precise adjustment of ID current, better thermal stability)
  7. Built-in Schottky diode protection for the input and output (necessary real-life operation)
  8. Improving the operation of the protection relay (special PTT control is not needed)
 
By inverting the control of K1 security relay the input of the preamp without 12V supply voltage is short-circuited continuously. If connecting 12 V on the preamp, the relay will switch off and the preamp will work properly. The working method is the same even if powered through antenna feed or separately (via C21), so separate connectors and cables are not needed for the control.

 

The layout of the PCB can be found below. Dimensions are 72 x 34,5 mm.

Noise Figure:

Schematic diagram

Part list

Other photos:

Available completed and tested:

- With N male / N female connectors
- With N female / N female Connectors

- With BNC connectors

-Pretuned PCB without box and connectors

Contact me!