Example of proper commercial waveguide diode detectors/mixers.

WR-90 (X-band) on the left, WR-42 (K-band, from an old radar gun) in the middle, WR-28 (Ka-Band) on the right.

Plastic horn antennas.

A commercial one is on the left, a 3D printed one is on the right.

The 3D printed one will need to be coated with a conduction spray paint.

This can be handy for hiding from metal detectors.

Example of two modern X/K/Ka-band radar detectors.

The "rear" connection is usually a Gunn diode mounted in a cavity used for the local oscillator frequency (usually around 11.5 GHz).  The "front" connection is usually a mixer diode used for the IF output.

Bottom view of the detectors.  The screws are used for tuning.

Examples of some older X-band radar detectors.

Alternate view.

These older radar detectors used 1N23-style point-contact mixer diodes.

Looking down the horn of a modern radar detector showing the Schottky diode up font.

Example of the low-cost (but reliable) construction of an old Uniden X-band radar detector Gunn oscillator module.

The narrow section is the Gunn diode cavity for the 11.5 GHz local oscillator.

The 1N23 diode mixer mounted in front of it.

Commercial Ka-band Doppler speed radar modules.

Ka-band radar module with the horn antenna removed.

The mixer section is on the left, turnstile antenna (circular) post in the middle, and 36 GHz Gunn oscillator is on the right.