Blonder Tongue AM-60-860 to get around the house..

[Electronic M]

The first number is the output power in dBmV the second number is the maximum frequency it can make*. An AM40 can transmit usablly with well tuned antennas, but an AM60 is better.

*The 550 can't do UHF but the 860 can, both will do VHF and most CATV channels... Generally VHF is the best place to start out as it tends to be easier to set up and if you collect any pre-1964 sets some of your TVs probably don't have UHF.
That said there's nothing wrong with getting one that can do UHF...All your doing is the equivalent of getting a cheap muscle car and refusing to drag race it or take it over 70 on the interstate.