BPFs: 1015204080160

Please, see 40M High Power BPF made in a smaller enclosure.

Recommended Band Pass filter applied power with antenna VSWR <1.5:

  • 100 CFM fan installed – 3000W CW/SSB (2500W RTTY) 
  • 50 CFM fan installed – 1500W CW/SSB/RTTY
  • Without fan installed – 1000W 

Enclosure is Hammond 1411ZU :

  • Without Fan – 17 x 4″x 5″ (42.5 x 10.5 x 12.5 cm)
  •  With Fan Installed –  18″x 4″x 5″ (46 x 10.5 x 12.5 cm)


In general, schematics is the 5th order Chebyshev inductor-coupled BPF.

  • Insertion Loss < 0.32 dB
  • Band Isolation ( 80M > 60dB, 20M > 70dB, 15M >100dB)
  • VSWR < 1.1 (RL > 26 dB)


VSWR and Insertion Loss inside the 40M band:


I build another HP 40M BPF using large Iron Powder toroids.

  • More than -80dB isolation level can be achieved for 20M band  if large toroids used instead of large coupling air coils (see photo above). Coils made on toroids have less stray capacitance (parasitic capacitance between coil turns) and as a result higher band isolation gets improved.
  • T200-2 iron power core can be used up to 2000W of amplifier output power without any problem.  

Please, see a graph below with T200-2 used as coupling inductors with -85dB of 20M band isolation:


Please, see a photo below with T200-2 toroids used as coupling inductors  for 40M BPF:

40M_Toroids 001

On a picture below you can see 40 and 80 meter band BPFs.  80M BPF box twice deeper than all other band BPF boxes.

VE5MX_40_80 006