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|
|4O3A||< 0.46 dB||> 66 dB||> 66 dB|
- 4O3A and RA6LBS higher band isolation delivered by a higher Insertion Loss (-0.46dB is 11% of output power loss).
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.
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.