Great article and it really takes me back to my past! I was fortunate enough to always have a VM700 or equivalent to assess the quality of my modulators but one low channel isn't it of reach. One quibble with:

> After realizing that broadcast television uses negative modulation ...

NTSC is actually vestigial side-band so while it's easy to notice the modulation below the carrier, the low frequencies which include the sync information are also present above the carrier with the effect of having twice the modulated power.

A cheap and dirty alternative to this excellent effort is to use an old VCR. Run your content into its input jacks, but instead of cabling the VCR directly to an analogue TV, use its RF output fed into an antenna, and use the analogue TV's tuner to receive. On most North American VCRs, that would mean selecting either output channel 3 or 4. For larger coverage areas, cut two dipole antennas to the appropriate size for the selected channel (one antenna for TX, one for RX). If you were to put a low noise VHF-LO amp inline between the VCR output and the TX antenna, you'd be able to cover a much larger area, but would probably have legal issues with governmental authorities in charge of telecommunication spectrum.

Super cool, tyvm