Rca1948FrequencyModu.. - The New Jersey Antique Radio Club

COMMON- AND ADJACENT-CHANNEL INTERFERENCE 321Sometimes during hot weather, or before a storm, long-distance transmissionhas been observed from frequency modulation broadcast stations.During the summer of1944, station WSM-FM in Nashville, Tenn. washeard often in Camden, New Jersey. During July it was very strongand free of noise for nine evenings in succession and it was heard severalother evenings. Occasionally, long-distance reception from stations in alldirections was observed. On July 7, 1944 nearly all the mid-westernstations and several from other directions could be received in Camden,for about 2^2 hours with a standard commercial receiver and indoorsantenna. The following list of stations received was compiled that evening:Call Station MegacyclesWWZR Zenith Radio Corp., Chicago 45.1WGNB WGN, Inc., Chicago 45.9WBBM-FM Columbia Broadcasting System, Chicago 46.7WDLM Moody Bible Institute, Chicago 47.5WSBF South Bend Tribune, South Bend, Ind. 47.1WMLL Evansville on the Air, Evansville, Indiana 44.5WENA Evening News Assn., Detroit 44.5WMFM The Journal Company, Milwaukee, Wisconsin 45.4WSM-FM National Life & Accident Ins. Co.,Nashville, Tenn. 44.7WMIT Gordon Gray, Winston-Salem, N. C. 44.1WMTW Yankee Network, Mt. Washington, N. H. 43.9W2XMN Edwin H. Armstrong, New York 43.1WHNF Marcus Loew Booking Agency, New York 46.3WBAM Bamberger Broadcasting Service, New York 47.1WABC-FM Columbia Broadcasting System, New York 46.7WABF Metropolitan Television, Inc., New York 47.5WIP-FM Pennsylvania Broadcasting Co., Philadelphia 44.9Some interesting common-channel phenomena were observed.StationsWENA, Detroit, and WMLL, Evansville, were of nearly equal strength.First one, and then the other was received; they changed about everyfifteen seconds.There would be a slight amount of noise and the programswould suddenly be interchanged. This continued for about one-half hour.Sometimes the carrier-wave voltage levels dropped below the level atwhich the limiter inheard simultaneously.the receiver operated and both programs could beStations WSBF, South Bend, and WBAM, New York, were also in acommon channel.WSBF was stronger and was clear most of the time;WBAM would come in with sudden bursts of a word or two or a bit ofmusic as station WSBF faded rapidly. These bursts occurred at intervalof about ten seconds.