Preselector Filters for 80m and 160m CW
The purpose of these filters is to
provide some relief to an RX. They could make the difference
mainly when beverages antennas are in use where quite a
broad-band signal is comming to the input of the RX.
They preselect the CW portion of the band for either 80m and
160m.
 Prototyping stage using a bread-board and nanoVNA. |
 Top view of the PCBs. The upper one is 160m, the bottom one is 80m. |
 The bottom view of PCBs.. |
 The foam polyuretan is used to fix the PCBs in the alluminium housing. |
 The result. |
 nanoVNA did a great job in tuning of the filters. |
| 80m | 160m | |
| L1 | 2 turns/20 turns wire
Ø0.5mm torroid Ø10mm, N1 Pramet Šumperk |
2 turns/25 turns wire
Ø0.4mm torroid Ø10mm, N1 Pramet Šumperk |
| C1 | 82pF | 270pF |
| C2 | 22pF | 27pF |
| C3 | trimmer 6.5 ... 30pF | trimmer 6.5 ... 30pF |
| C4 | 6.8pF | 12pF |