Some frequencies of electromagnetic waves are used for transmission of information, like radiowaves, microwaves, light, but some are not..
What about low frequencies?
Perhaps low frequencies aren't used for transmission simply because the waves haven't got enough energy to reach the destination, but it's well-known that if you go near a high voltage transmission tower, you can turn on a fluorescent lamp http://www.electric-fields.bris.ac.uk/
Perhaps the intensity of the high voltage gives more photons to interact there, than in a home installation, but the fact is waves are traveling anyway at 50/60 Hz without need any modulation.
There is a limit on how low a frequency can be to put photons into travel?