Re: HU from US : Use HD Radio attachment to tune in missing stations Quote:
Originally Posted by DerAlte Yes, yes, yes, please explain, Navin! |
If you look up FCC's website you will get this....or something like this..(my copy paste if from their old website and I have not checked recently). The FM broadcast in the United States starts at 88.0 MHz and ends at 108.0 MHz. The band is divided into 100 channels, each 200 kHz (0.2 MHz) wide. The center frequency is located at half the bandwidth of the FM Channel, or 100 kHz (0.1 MHz) up from the lower end of the channel. For example, the center frequency for Channel 201 (the first FM channel) is 88.0 MHz + 0.1 MHz = 88.1 MHz....
This has been their line since the early 1980s (or maybe late 1970s). No where did they explain why they started called 88.1Mhz Channel 201 why not Channel 1? So I did some digging literally. From what I seem to remember (I have a vague recollection of this so google-meisters please forgive me) the orignal radio channels were designated numbers 21-99. So initially there were 80 channels. 80 channels across 8Mhz (42-50 Mhz). So the FCC had initially allocated spectrum 100kHz (0.1Mhz apart)! Also this explains why when the FCC went from 42Mhz to 88Mhz and 100 channels they just put a "0" between the 2 and 1 of 21 and numbered the channels 201 onwards. If you ever took old valve radios (Philco, GE, etc..) apart you will see that the channel numbers running from 21-99 in the pre 1940 radios and 201-300 in the post 1945 radios.
So why the change....before we take 1 step forward lets take 2 steps back. All the way to a fellow called Edwin Armstrong. This Armstrong fella was the most vocal proponent of FM in the 1920s and 30s. After a lot of pushing and shoving and proving that FM was indeed viable the FCC initally had granted 41-44Mhz to FM. This is later expanded to the 42-50Mhz (again there are long sordid sotires my dad had told me about this part but that is a whole different discussion). Anyway after the war (WWII) the FCC moved the radio stations from 42-50 Mhz to 88-108Mhz to make way for Television. Why I have no idea. Why did FCC not just allocate TV the higher frequencies?
Apparently this move made all of Armstrong's equipment (by then Armstrong had a business of making FM recivers and transmitters and had many patents etc...) redundant and the man who invented FM committed suicide.
To quote Trevor Horn "Video" had indeed killed the "Radio" star!.
If you listen to the song carefully he starts by saying "I heard you on the wireless back in 52". Edwin Armstrong died in 1953 or 54. Was this a direct reference that no one understood? or have I played way too many records backwards?
So why are US radio stations seperated by 200kHz instead of 100kHz like almost everyone else? The difference stems from the regulations laid down by the FCC. The FCC regulations on broadcast interference stipulate that the pass band be +/- 75kHz (not +/- 50kHz as across the EU). This allows for more powerful antennas to broadcast and cover the larger area of the US without interfering with neighbouring stations. This also allows small community based radio stations to co-exist alongside the big radio stations (the FCC has at least 3 different classes of Radio stations). The EU is limted by language and terrain and hence does not need high power radio stations; local dialects and languages across the EU ensure a sense of community exists. Also there is more congestion in the EU hence the 88-108 band is divided into 200 channels in the EU but only needs to be divided into 100 channels in the US.
This is as simple as I cam make it. There are a few other reasons best understood by Marconi, Armstrong and others.
Last edited by navin : 5th May 2011 at 10:05.
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