I had some WR-15 and WR-10 AM waveguides made on the Protolabs AlSi10Mg high-res process. I did not use a choke but I did have the flanges polished; they will do that.

Sounds promising! An no significant loss across the flange connection?

The WR-15 worked well. For a 3” length, the insertion loss was 0.3 dB, compared to 0.2 dB for the 3” reference. The WR-10 did not work well.

The surface roughness models in the 3D simulators do not work well; they overestimate the loss for the rather rough surface.

I had previously stated the flange was polished. It was just machined flat. I suppose you could polish it, but the machining is probably adequate.

I don’t know how high-Q structures would perform. I’d like to make a WR-15 filter or resonator; just no time.

My recollection about choked flanges were that they were intended to mitigate power leakage escaping from the mated flanges. But this was specifically relevant to microwave installations involving high average transmit power, e.g. more than 5 kW, where leaked power could be troublesome.

That would make a lot of sense; thanks for that! All the more reason for us to omit it from our design (K-band satellite transceiver won't output anywhere near 5 kW).