| Please refer to the handy toroidal calculation table for the number of coil turns. |
| 4-element BPF |
4-element BPF circuit diagram file The 4ELE-BPF was used in the MT-Pluto and Neptune direct receivers. The circuit diagram shows the constants for each band and how to wind the coils, so please refer to it. Band switching is decoded with a 74HC138, but it can be selected by simply connecting the digital transistor's input terminal to GND. This unit is a narrowband filter that tracks the in-band tuning frequency only for the AM band. It is recommended to adjust each band with a TG-spectrum analyzer, but the characteristics can also be used by adjusting each trimmer so that the carrier at the center frequency has maximum amplitude. When winding a toroidal core by hand, please refer to the handy item 'Toroidal Calculation Table'. |
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3.5M/3.8M-BAND Actual measurement |
7M-BAND Actual measurement |
| 3-element BPF |
| I used LTspice to simulate the 3-pole Chebyshev BPF, which I use most often in my home-built equipment, and I have posted the circuit diagram and the simulation results for each band below. With this BPF, you can get a nice flat characteristic within the band by finely adjusting the tuning capacitor (used in conjunction with a trimmer capacitor in the actual equipment). (Click to enlarge) | |
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3 element BPF circuit diagram file 3ELE-BPF was used for TX-Neptune/TX-Uranus. It is a pain to make it by hand-wound on a toroidal core, so I cut corners a little. Rather, I designed it with 3ELE because the characteristics are satisfactory enough. Each constant is listed in the circuit diagram. |
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3.5M/3.8M-BAND Actual measurement |
7M-BAND Actual measurement |
14M-BAND Actual measurement |
21M-BAND Actual
measurement |
28M-BAND Actual measurement |