This page dedicated to a low and high power diplexer design and implementation.

I would start with low power diplexer. 

The design is a combination of LPF and HPF circuits with LC traps for 40 and 80 meter bands to increase band isolation.

Some numbers I achieved for 200 watt diplexer:

  • Insertion Loss (IL) < 0.1dB.
  • Band Isolation > -35dB for 40M band 
  • Band Isolation > -30dB for 3.5-3.8 MHZ (lower isolation above 3.8MHz) 
  • Return Loss (RL) > 27dB
  • 100 watt output power with 100% cycle
  • 200 watt output power PEP

Hiro 001

Please, see schematics below – a Cauer (Elliptic)  type. 

40_80_Dip_Elliptic

Please, see schematics below – a Chebyshev type. 

40_80_Dip_Chebyshev

Please, see Diplexer low power graphs below built based on a Cauer type.

  • The difference between filter types is not a significant to discuss it but two schematics allows to chose more suitable capacitor’s values.

Hiro_35_Wide

Hiro_7_Wide


Below is a High Power Diplexer for 40 and 80 meter rated at 3000 watts of an amplifier output power.

Diplexer_40_80_HPInsertion Loss (IL) < 0.08dB

  • Band Isolation > -35dB for 7.0-7.3 MHz 
  • Band Isolation > -30dB for 3.5-3.8 MHZ  
  • Return Loss (RL) > 30dB
  • 1500 watt output power with 100% cycle no cooling required
  • 3000 watt output power (50 CFM cooling fan recommended)
  • 1411ZU 17″ long Hammond enclosure

The 40M band below:

EA8KW_Diplexer_40

The 80M band below:

EA8KW_Diplexer_80

Graph below is an Impedance ([Zs]) and VSWR  from Antenna port:

EA8KW_Diplexer_ANT_Port

Diplexer_40_80_HP