OK troops, I'm about to embark on my own product test. I have ordered the AMM-SD1 Series AM Modulation Monitor from http://www.radioassociates.com/ . I will be prepared to test it compared to a freshly calibrated and certified Belar Mod Monitor that I use at the transmitter of the commercial AM I work for. I will be able to test/compare in three ways -- direct readings from the mod monitor output on a new 5,000 watt transmitter, readings from part 15 transmitter received off a loop sampling antenna near the transmitting antenna, and modulation tests from various stations including my Part 15 utilizing the IF of a receiver.
this is just one of those setups I couldn't resist trying out and since I'm in a position to test and compare with known professional equipment I can see how it stacks up. Results may take a while. The off-air/part 15/receiver pickup is backordered for about two weeks.
Of course I have many other applications for this if it works as advertised with reasonable accuracy.
I'll keep you posted.
Tim in Bovey