>> AM radio would be nearly useless without those 50,000 watt broadcast stations.
Actually, there are a limited number of those clear channel 50KW stations, and for obvious reasons, a limited number of clear channels for them to broadcast on.
Most AM stations have much more modest power levels, and Class 4 local stations have to lower power after sunset to near-microscopic levels to minimize interference to other stations on co- and adjacent channels.
In 2009, the AM station for which I provide engineering moved transmitter sites, constructing a new building and antenna array. By the time it was over, the owner had $130k into it (including the land). We lost 10% of our daytime power in the relicensing (1KW down to 900W) and nightime power went from 60W to 39W. The station covers the local market well during the day, but after dark, it's basically useless unless you live a few blocks from the transmitter site.
The only thing that made the move and expense worthwhile was purchasing and applying for a license to rebroadcast the AM program material on an FM translator (250W ERP output maximum). The FM translator more than covers the community, and it doesn't have to be turned down at night.
As great as the FM translator sounds (full-fidelity, stereo!), we still have listeners who refuse to listen to it, and who complain bitterly if the AM isn't sounding up to par (it's a format of vintage tunes that appeals to retirees).
The buzz in the broadcast industry is that the AM band is on life support, and will eventually be taken away and auctioned off as available spectrum for other purposes. Licensees of AM stations are digging in, assuming that there will be some lucrative compensation for the loss of their AM licenses, either a buy-out, or a license in some other (perhaps not-yet created) broadcast service.
The carmakers solution to QRM (interference) has been to offer only FM radios and satellite (XM Radio) in their EV's. Why try to mitigate noise when "Nobody listens to AM any more?"
Of course, all broadcast is gravitating to forms of digital delivery, but my experience is that while analog (AM, FM, and TV) is at least listenable/viewable when there is weak signal or moderate interference, digital stations are the classic digital 1 or 0, it's either there, or it's not, nothing in between. Get out on the fringes of reception, and it all goes away, not even a sputter to give you a ray of hope.
Apparently FEMA still has faith in AM powerhouse stations, they've hardened and outfitted a bunch of those 50KW'ers with EMP-proof shelters with complete backup transmission systems and generators with 5,000 gallon diesel tanks.
Maybe AM will survive the electrification of the transportation system as well. _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub ARCHIVE: http://www.evdl.org/archive/index.html INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
