Since you have rabbit ears and hoops on all of them, the modulator is a much, much easier way to do it.
I have a Blonder-Tongue AM40-550, and you can find them on eBay for around 50 bucks, running the risk that it won't work, or needs new filters or whatever.
Another option is to buy a new one. I just picked up the PAL version of
this. It's rated at the same output as the B-T (99dBuV), is about the size of a pack of playing cards, and works great - I've just got a UHF hoop antenna connected to mine and I have a clear signal throughout a 3-story house on channel 25. Rock solid reception and really great picture quality (I'm feeding it from the composite output of a DVB-T STB). It does get quite warm in operation.
So, 69 bucks, you connect power and two cables plus a pair of rabbit ears, and problem solved.