The filter was build in a tin box 160x100x50mm. All inductors are wound on a 20mm dia. Wire thickness is 2mm copper wire. Capacitors are ATC800 series these can be replaced by doorknob capacitors or any othe capacitor suitable for the power used..
![](https://pa3csg.nl/wp-content/uploads/2024/06/50MHz-cauer-LPF-foto-1024x628.jpeg)
The schematic looks as follows:
![](https://pa3csg.nl/wp-content/uploads/2024/06/50MHz-LPF-Cauer-1024x526.png)
Component | Value |
---|---|
L1 | 3 turns 20mm dia 30mm long |
L2 | 4 turns 22mm dia 30mm long |
L3 | 4 turns 25mm dia 30mm long |
L4 | 1 turns 20mm dia 20mm long |
L5 | 1 turns 20mm dia 10mm long |
C1 | 68pF |
C2 | 68pF |
C3 | 39pF |
The suppression of the second harmonic is good. If more attention was payed to the shielding of the individual inductors -50dB would be possible. The input match is good with -25dB and was easy to obtain.
![](https://pa3csg.nl/wp-content/uploads/2024/06/50MHz-cauer-LPF-plot-1024x633.jpeg)