[ChrisW6ATV]

Sandy-

You need to be sure to get modulators, not DEmodulators (maybe that was just a mistake in the description). The '450 versus the '550 just cannot go as high in frequency (but we will not care for our use with antique TVs), and the AM40 has lower signal output versus the AM60, which should only be important if you do want to try using one of these devices as a true over-the-air in-house transmitter (then get the AM60-450 or AM60-550). Phil's site is a treasure of great information. You can either try this "in-the-air" method with antennas on each TV, or put a multiple-output splitter on the output of the modulator and run coax to each TV, with a matching transformer on each one.

Eric, I may have had that problem too (I have not tried one of my modulators in a while), and one trick may be to put a "grounding adapter" on the modulator's power cord. This is the gadget that has a three-prong AC outlet on one end and a two-prong plug, with a pigtail or metal loop for the ground (that in this case you will NOT connect). The idea is to not use the grounding connection on the modulator's cord, to avoid a ground-loop problem that can happen when commercial items like the modulator are mixed with consumer two-prong items like a DVD player or digital-TV tuner.