I was just doodling around and the thought occurred to me...just how many 50,000-watt radio stations do we have in North America?
So, a Google Search led me to this:
http://www.northpine.com/broadcast/50kwam.html
From 540 to 1580 kc's...I wonder why not in the Extended Band (1610-1710)? Maybe because it is so "open" or "clear"? I'll have to look into it....By the way, there are several duplicated frequencies; differing directional patterns help reduce or eliminate interference to the targeted areas.
I may try to log a bunch of these...some will be harder than others, due to their directional (or lack thereof) patterns...but, it'll be fun to try! So, on a weekend, I'll fire up the Kenwood TS-140S Ham rig and the Hammarlund HQ-100A shortwave receiver, and maybe the Realistic DX-400, plug in some different antennas and try my hand at it.
Bud S. (staceys4@hotmail.com)
I think there is a low power limitation for all AM broadcast stations operating on 1610 KHz or higher. The local station in Chicago was operating 10 KW during the day, but they were required to reduce their power to 1 KW at night on their 1690 frequency. They continuously claimed they were applying to the FCC for authority to use 10 KW at night. The station changed format; therefore, I lost interest in following their fight for more power. The whole idea of having an expanded band was to give some low and medium power broadcasters a chance to have a signal without having nearby competition on the same frequency. I remember reading all of the stations in the newly expanded part of the AM band were going to be required to run AM stereo. It seems that requirement has been forgotten. There is another point of relevance: they could not be authorized a frequency which was twice the frequency of any other local station because of the possibility of harmonic interference. As an example, 1700 KHz could not be licensed if there was a station in the same area operating on 850 KHz. This seems strange to me because I thought harmonic radiation was not a huge problem in the AM broadcast band. I won't try to explain image frequencies, but they are a problem caused by a deficiency in the typical AM receiver. These phantom signals usually appear 910 KHz above the station's actual transmitting frequency. One might hear these phantom signals on his or her radio if it is tuned to the upper end of the band, and there is a local station operating in the lower end of the band. There is a good explanation at www.radioremembered.org/imgfreq.htm .
ReplyDeleteIt is my guess receiver image frequencies would be more of a problem than harmonic radiation from today's sophisticated transmitters. Any comments are welcome?
Ron Henselman W9FT Melrose Park
Thanks Bud,
ReplyDeleteThat list from your Google search will make a nice addition to my National Radio Club's AM Radio Log which I refer to when looking up MW broadcasters from time to time. Happy dxing.