20M HP BPF comparison (websites can be opened by links):

Insertion Loss 40M Isolation 15M Isolation
VA6AM  < 0.3 dB > 67  dB > 63 dB
DXEngineering(LBS) < 0.47 dB > 74 dB > 74 dB
DXEngineering (DX-S) < 0.4 dB > 54 dB > 78dB
4O3A < 0.46 dB > 66 dB > 66 dB

Recommended BPF Power with antenna VSWR <1.5:

  • 85 CFM fan installed – 3000W CW/SSB (2500W RTTY) 
  • 50 CFM fan installed – 2000W PEP CW/SSB/RTTY
  • Without fan installed – 1500W PEP  

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.

20M band BPF is the best performer by all numbers: high band isolation, low loss and a perfect impedance matching. Band-pass for VSWR by level of 1.2 is more than 3MHz wide and by level below 1.1 is almost 2MHz wide.

  • Insertion Loss < 0.30 dB
  • Band Isolation ( 40M > 67dB, 15M > 62dB, 10M >87dB)
  • VSWR < 1.1 (RL > 28 dB)


VSWR and Insertion Loss inside the 20M band:


Zs is another good parameter to know. It should be as close to 50 Ohm as possible.


Please, see a graph below of the Triplexer and 20M BPF connected as a whole Tribander set.

20M band BPF + Triplexer (other triplexer band ports terminated by 50 ohm loads):

  • Insertion Loss < 0.4dB
  • Band Isolation ( 15M > 95dB, 10M   > 110 dB under VNA noise floor, 40M > 67dB)
  • VSWR < 1.1  (Return Loss > 26 dB)


The next graph below is for 20M BPF and Triplexer together when other triplexer band ports connected not to  a perfect 50Ohm load but to real 10 and 15 meter BPFs.

Now, when Triplexer connected to other BPFs the 20M graph is a little different because real BPFs are not a perfect 50 ohm loads and have their own reactances.

I should mention that no parameters influenced by this, SWR and Isolation level are still good.

Graph below is a 20M band BPF + Triplexer (All BPFs connected to the triplexer):


This 20M BPF  together with Triplexer was a very good performer without overheating with 3000 watt applied , with low Insertion Loss and well below -90dB of an adjacent band isolation level.

Doorknob capacitors used allow to use it up to 4500-5000 PEP output power but I was able to test it with 3000 watts.

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

K8AZ 003