In the Boston area we had 2 OTA pay TV stations in the late 70's
Ch 27 in Worcester ( Wistah in NE speak) used the Zenith system &
Ch 68 from Boston ( B-T system ??). IIRC Ch 68 used circular polarization. On
the biggest UHF antennas it was always very snowy even at +- 30 miles.
Both installed cut to freq antenna & the signal from CH 68 was rock solid.
Just before OTA pay died "someone" sold off boxes for a few hundred $$ each.
It lasted about a year then back to unscrambled NTSC. Gee I wonder who
was selling them
73 Zeno
LFOD !