Coils...12 SWG wire. 6 turns. 8mm internal diameter. Coil length 19mm.
Capacitors...High Voltage ceramic or Mica. 110pf Cap is 100pf and 10pf in parallel.
A suitable enclosure might be a diecast box with the filter built on copper clad board. Note the screen which can be made from the pcb material as well. If you can live with a slightly lower performance in terms of filtering, you can omit the internal screens but make sure you put it in a metal box.
3 comments:
Perfect. Thanks for sharing.
I built this, but it did not turn out great. The thing has an SWR of over 3 with a dummyload after it on both bands (both on a NanoVNA and a transceiver. The dummyload has 1.0). The coils initially measured 0.33 instead of 0.27uH, and did thus not reach the 19mm length, so I dragged them apart a bit, but it did not help.
Anything sticking out as bad construction wise here?
https://postimg.cc/gallery/mMyd1vV
Hard to know. Find a plastic stick. put ferrite one end and brass the other. Insert them into the coils and see what happens. ferrite lowers the freq while brass raises. Those coils look like they are to high in freq.. Try thinner gauge and experiment with more turns.
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