BPFs: 1015204080160

For 80M BPF I used a twice wider enclosure to fit in all large coils.  I have to use MFJ amplifier coils to make up a large inductance for coils. Some large capacitance made of three doorknob capacitors in parallel. All these factors has brought price up.

Two 50 CFM fans installed to get a suffucient air flow to the larger box.

Recommended BPF Power with antenna VSWR <1.5:

  • 3000W CW/SSB (2500W RTTY) 
  • Without fan installed – 1500W 

Enclosure is Hammond 1411ZU :

  • Without Fan – 17 x 10″x 4″ (42.5 x 25 x 12.5 cm)
  • With Fan Installed –  18″x 10″x 4″ (46 x 25 x 12.5 cm)




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

  • Insertion Loss < 0.40 dB
  • Band Isolation ( 160M > 72dB, 40M > 70dB)
  • Band Isolation is 20dB better than BPF from 4O3A with lower insertion loss
  • VSWR < 1.1 (RL > 25 dB) , 3.8-4.0 MHz VSWR <1.2


VSWR and Insertion Loss inside the 80M band below.  As 80M band relatively wide that is why the VSWR is going to 1.2 value closer to 4MHz upper band edge.


Doorknob capacitors, used three in parallel, allow to use it up to 5000-6000 PEP output power but I’ve never tested it with this power. For this output power some coils should be made with  a larger wire diameter.