Here are the results of two QRP Labs projects over the past year, both of which make use of the QRP Labs
Arduino shield. The first uses the shield together with the QRP Labs Si5351a module (borrowed from my
U3S) as LO for the receiver module. In the attached picture, a 20 meter BPF is plugged into
the receiver module, with the LO generating 56.8 (or thereabouts) MHz. It makes quite a hot 20 meter SSB receiver!
The other is a scalar network analyzer, based on a design by VE3MKC.
Here, the shield has an AD9850 module mounted, along with (in this case) that same 20 meter BPF,
plugged into the board. That Altoids container provides shielding for an AD8307 module, that measures
input power and outputs a number back to the Arduino board. Last pic is the response curve for that BPF.