At 5/25/2011 03:42 PM, you wrote: >Content-Type: multipart/alternative; > boundary="----=_NextPart_000_000E_01CC1AD9.4A1976F0" >Content-Language: en-us > >Hello all > >Can anybody on the list assist or point out links to find out more >on FM radio (87.5 108MHz) band plan and regulations regarding the >FM radio stations and it transmitters. > >My question is In practical what is the minimum distance (FM zone) >between FM stations and the transmitter power output can be used >without causing any interference between the 2 stations, say station >A operating on 87.5MHz and station B operating on 87.7MHz within the >same small town/village. What is the minimum spacing (KHz) can be >used if the 2 stations operate in the same town each operating on 100KW > >Thank you in advance
The FCC rules for FM stations work two ways. Commercial stations (92 MHz up) are based on a Table of Allocations, which is only modified by petition. It has to meet interference rules but that alone doesn't dictate what can be done. Stations are assigned license classes, each with power limits, and there is a table of distances required between stations of certain classes at given channel spacing (0-3 channels). These hve gotten complex. The educational band (below 92) is generally licensed based on non-interference rules. Low-power stations on any frequency are also based on non-interference rules. These have, I think, recently changed. Under these rules, which also apply to "short-spaced" allocations, stations are "protected" out to a certain predicted signal strength contour. The signal within the protected contour is then protected against interference by certain limits. Co-channel interference must be 20 dB less than the protected signal. Adjacent-channel interference must be 6 dB less. A 2nd or 3rd adjacent channel (400-600 kHz) must be no more than 40 dB more than the protected signal. I think the Low Power FM rules are more tolerant, and no longer protect third-adjacent channels, but this was overriden by Congress (thanks, NAB :-( ) and only overturned last December. So the FCC will have new looser rules, but I haven't seen the final text. FM broadcasting is in the FCC Rules Part 73. Here's a copy: http://louise.hallikainen.org/FCC/FccRules/2010/73/ -- Fred Goldstein k1io fgoldstein "at" ionary.com ionary Consulting http://www.ionary.com/ +1 617 795 2701 -------------------------------------------------------------------------------- WISPA Wants You! Join today! http://signup.wispa.org/ -------------------------------------------------------------------------------- WISPA Wireless List: wireless@wispa.org Subscribe/Unsubscribe: http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/
