BPFs: 1015204080160

Recommended BPF Power with antenna VSWR <1.5:

  • 100 CFM fan installed – 2500W CW/SSB (2000W RTTY) 
  • 50 CFM fan installed – 1500W CW/SSB (1000W RTTY)
  • Without fan installed -1000W CW/SSB PEP (750W RTTY)

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)

Below, all three BPFs for 10, 15 and 20 meter bands to be used with the triplexer.

4X6FR 006

  • I’ve built two different design BPFs for 10M band. One is 4th order capacitor-coupled BPF type and another is a 3rd order with HPF added.

It turned out that 10M BPF is the most difficult to get a good parameters as all final parameters are very sensitive for  coil and capacitor values.

Please, see the 4th order one below:


This particular 10M BPF  above built  with Teflon sheet based capacitors. It is a nice construction idea but it turned out not a reliable type of capacitors and can be used only up to 1000 watts with a good SWR antennas.

The results I achieved for this type:

  • Insertion Loss < 0.45dB
  • Band Isolation ( 15M > 58 dB, 20M > 100dB)
  • VSWR <1.1 (Return Loss >26 dB)

10M Wide

The drawback of the design is a higher Insertion Loss with power dissipated mostly on a central coil of the filter. That coil can get really hot and required a very intense cooling air flow when applied power is above 1000 watts. With 1000W PEP this BPFs is a good performer.

Below is 3rd order 10M BPF with HPF and 15M LC trap


The next 10M BPF design developed  to improve the Insertion Loss. Insertion Loss expected to be lower  and as a result of it less air flow could be required. The idea is to use lower order BPF with added HPF and 15M LC trap to improve isolation level.

Please, see 3rd order 10M BPF with HPF added below:

  • Insertion Loss < 0.3 dB
  • Band Isolation ( 15 M > 65 dB, 20 M > 84dB)
  • VSWR <1.1 (Return Loss >26 dB for 28-29 MHz )



This 10M 3rd order type with HPF has less insertion loss and has all coils in better condition with less cooling air flow . 

Please, see a graph below of the Triplexer and 10M BPF (later design) connected as a whole tribander set.

  • Insertion Loss < 0.35 dB
  • Band Isolation ( 15 M > 90 dB, 20 M > 120dB)
  • VSWR 26 dB (for 28-29 MHz )


  • I would like to point out to a very low Insertion Loss of -0.35dB for the whole set of triplexer with attached 10M BPF and this is a very good result for an isolation level better than -90dB.
  • 20M band isolation level is much higher number than you can see on a graph above but VNA noise level hides the minimum point.