I completed low band 40, 80 and 160 High Power BPFs in a new smaller enclosure Hammond 1444-1773. This enclosure is only 3″ or 7.6cm of height. 

 It is the same DX-pedition style enclosure I used for 1500W Triplexer with BPFs set but 2″ (5cm) longer because I built them as the 5th order type  with Isolation better than -60dB.

  • 40 and 80 meter BPFs are the 5th order Chebyshev type
  • 160 meter filter is the 7th order Chebyshev type LPF
  • 1500W PEP without air cooling
  • 3000W PEP with cooling fans installed


This was quite a challenge to find a solution between required high Q coil factors which requires a large in size coils and a smaller 3″ tall enclosure.

Some coils made using Iron Powder cores T200-2 to solve the problem. My concern was how those toroids would behave when at least 1500 watt of output power applied.

I use those toroids where no high current expected. Those are all coupling coils in a filter circuits.

Please, see some graphs below:

  • 40M band with a re-calculated larger by value capacitors allowed me to build BPF with a regular made of copper wire but smaller in diameter coils compare it with a 3000W 40M BPF version in 1411ZU Hammond box. Please, see a photo below.

This BPF is good for up to 3000W if a proper  air cooling provided. This particular one was built without fans installed and tested with 1500 watt amplifier without any problems.

Capacitors which you can see on a photo is a large 55mm in diameter doorknob capacitors in parallel, 20KVar of a reactive power each.  They will survive 10kW of output power without any problem.

Box_1773 004

As it is 5th order BPF all numbers are quite good. Please, see some graphs below.

  • Insertion Loss < 0.35 dB
  • Band Isolation ( 80M > 60dB, 20M > 80dB, 15M >100dB)
  • VSWR < 1.1 (RL > 26 dB)


40M BPF In-Band graph below with VSWR and Insertion Loss.


  • The next band was 80M BPF where I used Micrometals T200-2 toroids. Please, see some photo and graphs below.

The same 1500W output power test result was very good. Toroid cores did not get any heat with a little warm wires. I used 1.9 mm magnet wire. The same large doorknob capacitors used as it was for 40M BPF.

7″ deep enclosure allows to install large doorknob capacitors with all available space for coils.

80M BPF was built for 3.5-3.8 MHz to be used in Europe, but it can be tuned much wider up to 4 MHz if required with VSWR below 1.1

80M_LY4L 003

  • Insertion Loss < 0.35 dB
  • Band Isolation ( 160M > 62dB, 40M > 75dB, 20M >100dB)
  • VSWR < 1.1 (RL > 26 dB)



  • For the 160M band a LPF (Low-Pass Filter) type was built. Result is very good with a very low Insertion Loss and very good band attenuation. Please, see some more information on a 160M LPF page.


  • Insertion Loss < 0.15 dB
  • Band Isolation ( 80M > 65dB, 40M > 80dB)
  • VSWR < 1.1 (RL > 26 dB)



Please, see BPFs in my standard Hammond 1411ZU enclosure: 1015204080