Input BPF for the Sudden Rx Shield

Correspondent Dave has stirred me into action to finally draw some schematics for the correct form for input band-pass filters for the Kanga-m0xpd Sudden Rx Shield.

I have previously described how the shield needs an input band-pass filter, best constructed with reference to the G-QRP's standard recipe, which implies a structure of the form suggested by the schematic below...

 

This will not work well with the Rx shield, due to the details of the earthing arrangements (as study of the Sudden Rx circuit will reveal).

Instead, a modified version of the filter is required, as drawn below...

The filter was correctly drawn in my previous instructions - but the schematics above emphasise the required filter network with a directness that was missing before.

All my BPF boards, including the switching, two-band filter for Occam's Dirk...

use this topology.

Thanks for Dave, ve3ooi, for prompting my activity - for the benefit of others!

...-.- de m0xpd