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 0.5mm
torroid 10mm, N1 Pramet Šumperk
2 turns/25 turns wire 0.4mm
torroid 10mm, N1 Pramet Šumperk
C1 82pF 270pF
C2 22pF 27pF
C3 trimmer 6.5 ... 30pF trimmer 6.5 ... 30pF
C4 6.8pF 12pF


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