Okay, so it's really antenna radiation pattern testing - but that isn't as catchy.

UV-82 radio & DMM Field Strength Meter

Yes, there is modeling software and, yes, it is accurate.  But nothing really beats a hard measurement.

 

My objective is to validate antenna radiation patterns.  Because I'm going for pattern, not true power levels, I will use relative values; whatever the meter gives me.  I will focus on the 2 meter band, 144 MHz to 148 MHz.

Before anyone freaks out, yes, I am a licensed amateur radio operator.

 

Phase 1 will be to verify my ability to measure RF signals.  The antenna will be a vertical dipole.  I should see roughly equal readings in all directions.

Phase 2 will be to test a 3-element yagi.  After measuring the 8 compass points (N, NE, E, SE, S, SW, W, NW), I will try to verify the shape of the forward lobe.

Phase 3 will be to test a 2-element cardioid pattern.  This is formed when two 1/4 wave antennas are placed 1/4 wavelength apart and one is fed 90 degrees out of phase.  It's a test question on the Technician exam.  I want to verify the single null to the rear.

 

The test equipment will basically be an RF detector circuit.  Preliminary testing with a Baofeng UV-82 and a RF detector circuit built into a Harbor Freight multimeter have proven successful.  It's at least at levels safe for an Arduino.

The RF detector was from QST magazine, "DMM Field Strength Meter", February 2015, page 71.  I found a very similar item on Instructables.com.  https://www.instructables.com/id/RF-Meter-for-Multimeter/

You can see that I took a few liberties with the DMM.  It will only be a RF meter for the rest of its life.  I will also be using this meter to "calibrate" the Arduino detector circuits to give similar readings.  They'll all be wrong together.