Propagation Question & Trivia Question
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  1. #1

    Propagation Question & Trivia Question

    Hello everyone, this is my first post here. I am interested in broadcasting history, especially AM radio and Chicago history. I have a technical question and a trivia question.

    On one occasion (that I know of) the FCC allowed daytime and limited time AM stations to stay on all night. Did the FCC or anyone make any observations of the skywave interference that this created? I suspect that the AM band was a mess. How many stations stayed on?

    Trivia question: What was the occasion that brought this about? Hint: It helps if you are over 65!

  2. #2
    Sputnik launch?

  3. #3
    Don't recall any particular incident, but Section 73.1250 allows AM stations to operate at full power or day mode in the event of an emergency.
    From Broadcast Law Blog from 2009:

    One of the rules highlighted by the FCC’s public notice is Section 73.1250(f) of the Commission’s Rules, which allows an AM station to operate at night with its daytime power in the event of an emergency. As many AMs operate only during daylight hours, and others routinely reduce power at night or use a directional antenna that restricts radiation in directions which may contain significant populations, this ability to continue to operate with daytime power and antenna pattern at night can allow a station to fully serve its community in times of emergency. However, a broadcaster taking advantage of this provision needs to observe the requirements of the rule. First, it must notify the FCC that it is operating under this rule within 48 hours of beginning to do so. If the station causes irreparable interference to another station, it may be forced to curtail such operations. Moreover, the operation must be on a noncommercial basis (apparently to limit any financial incentive for a station to abuse this provision). And finally, one issue not addressed in the FCC’s public notice about the Southern California fires, the use is only permitted if there is no other full-time service "serving the public need." Obviously, that last clause is open to interpretation, but it would certainly seem to preclude an AM daytimer co-owned and simulcasting an FM station that covers the same are from suddenly operating at night.

  4. #4

    Join Date
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    Only event big enough that far back would be the Kennedy Assassination. I was talking to the engineer on duty at one of our local (1 kw) Am stations. He told me that CBS had alert tones that would indicate the status of a bulletin coming through. He said it was the first (and only) time he ever heard 4 alert tones. Told me that he didn't even hesitate. Threw control right over to the network.

  5. #5
    Yes, it was the Kennedy assassination. As I recall, the FCC put out a general order that any daytime or limited time AM station could stay on the air all night. Many areas of the country lacked nighttime AM service and FM was not yet in some areas.

    At the time I worked for WJJD in Chicago (now WYLL), a limited time station on 1160 with KSL in Salt Lake City. I wonder what the skywave did to the AM band. Some stations generated more interference than useful service, I am sure. Did the FCC or anyone make any observations of the skywave?

    I have not found anything on the internet about this. If anyone has any information or corrections please post. This is all from my (senior) memory, so it may not be accurate!

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