Al Quaglieri wrote:

This is pure speculation on my part, but I can foresee a time when the
VHF/UHF bands become so clogged with highspeed data that less
glamorous operations such as regional/citywide paging, low-rate text
messaging, product ID tagging, water meter transponders, etc., go
looking for the lower frequencies. Without broadcast QRM, a relatively
modest paging transmitter on, say, 6.1 mHz could blanket a 10 mile
radius 24 hours with little of the line-of-sight problems of VHF.

Only problem with your scheme and frequency choice is that even very low
power signals can propagate at odd times. There are lots of hams
running 1 or 2 milliwatts and getting contacts on HF frequencies, and
signals from miles away would be just as receivable as those close by.
Instant interference. One of the reasons that VHF and up are so
desired for data is that they propagate less than HF and below.