rbrucecarter5 said:
I would call them pollution when they knowing violate their country's law by remaining on full daytime power at night. That is uncalled for - and I wish the Mexican authorities would crack down on the practice. It makes some frequencies unlistenable for both English and Spanish speaking listeners. I am sure an allocation plan could be mutually arrived at proportional to the populations of both countries.
The use of the spectrum on AM is regulated internationally, starting with NARBA and now with the "Comision Mixta" and takes into account generally accepted engineering practice, skywave propagation, etc.
Mexico has a lower number of AM's for the population than the US does, and has different engineering standards for its internal allocations. The use of directionals is much less, for example. What happened is that the US built out the band faster than Mexico did... in 1930 Mexico had a handfull of stations vs. hundreds and hundreds in the US, so many channels became unavailable for Mexican use.
Mexico considers "daytime" to be 6 AM to 7 PM, local time, every day. THis is in part because most of Mexico is closer to the equator, and the length of days does not vary as much as it might in Yakima or Bangor.
But, back to your statement: there is a procedure for usage of the AM dial in place and it has been working pretty well for two-thirds of a century. Like in the US, some stations will not comply with night power of sign-off times. But in the US we jokingly refer to the SFA, or "Special Football Autority" where daytimers don't sign off till after the Friday HS game or don't drop power.
Not all Mexican AMs heard in the US are operating illegally... having a Mexican station "owning" a frequency in Texas comes in part from the fact that Mexico is so close.
Oh, there is an FM system for stations within a certain distance of the mutual border, too.
As far as Mexicans keeping in touch with their homeland - that is the function of the shortwave band. There is a glut of Spanish language stations in this country, there is probably no place in the country where significant populations of Hispanics are not served by local radio (it seems to be the fashion these days to take underperforming stations Spanish).
In general, Mexicans resident in the US do not DX stations in Mexico. In years of diary reviews, I have never seen one mentioned even once.