Finally, I found a time to finish my design for all new Low Power band-pass filter PCB boards. Those boards designed to allow build filter types:
- Cauer (Elliptic)
- Chebyshev (W3NQN design)
- 10M BPF (VA6AM design)
Boards allow to use different capacitor types. Capacitors are the most difficult problem to solve as capacitor define the reliability of the BPF.
I plan to use a regular radial TDK capacitor or SMD (from American Technical Ceramics) capacitors, and also boards allow to use custom made MICA capacitors from Charcroft. I used those Charcroft capacitors before with a success but the production lead time is up to 3-4 weeks and some other capacitor types was considered as a replacement.
I recalculated filters with quadrifilar toroid turns to trifilar type where it was possible to decrease the potential voltage applied to capacitors and as a result of it to increase the capacitor reliability.
As always, the goal was not to achieve the maximum possible band attenuation but to find a balance between good isolation and low Insertion loss. Return Loss (VSWR) should be an easy to achieve parameter as well. I think if I can achieve -50-60dB of band attenuation it would be a great result which should meet a filter requirements for many different applications.
I think the filter Insertion Loss is a very important parameter to keep it as low as it is possible to reduce the heat dissipation and as a result of it to increase the filter reliability. Low Insertion Loss mostly defined ny Q-factor of coils and a proper coil design should be made.
Some bands already published before, like 10 and 20 meter bands but some will be the first to try with different design ideas.
To be continued….