Please, see 80M BPF built with large toroids as a coupling inductors in a smaller enclosure.
80M HP BPF comparison (websites can be opened by links):
|Insertion Loss||160M Isolation||40M Isolation|
|VA6AM||< 0.37 dB||> 62 dB||> 75 dB|
|DXEngineering (LBS)||< 0.18 dB||> 45 dB||> 47 dB|
|4O3A||< 0.47 dB||> 52 dB||> 51 dB|
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 > 65dB, 40M > 73dB)
- VSWR < 1.1 (RL > 25 dB)
Doorknob capacitors allow to use it up to 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.
Now, I build all 80M BPFs in a smaller box and with T200-2 toroids as coupling coils. Unfortunately, Ameritron coils sold by MFJ are not available all the time and those coils are too fragile.
The enclosure 1444-1783 used, 17″ x 8″ x 3″ with three 60mm fans installed for a better cooling those coils under the current stress.