This is essentially true but I'm not sure about the length of the off and on 
air intervals.  It was still being done when I started in the business in 
1972 and I seem to recall the intervals were more like 5 seconds.  Often the 
tone was on a tape cartridge along with the announcement and of course it 
exhibited all the flutter typical of many of those machines.  Lou  WA3MIX
Lou kolb
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----- Original Message ----- 
From: "Mike Keithley" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, December 07, 2011 2:52 PM
Subject: Re: A Bit of Radio History


> Concerning the 1 KHz tone, I seem to remember that there was 1 100 hertz 
> modulation tone associated with it.
>
> ----- Original Message -----
> From: Martin McCormick <[log in to unmask]>
> To:  [log in to unmask]
> Date: Monday, Nov 14, 2011 09:32:14
> Subject: Re: A Bit of Radio History
>
>>
>>
>> I do remember the CONELRAD tests.
>>
>> Radio and television stations would broadcast an
>> introductory message as to what was about to happen. The carrier
>> would go down for 15 seconds. Then, it would come back up for
>> another 15 seconds. It was down for yet another 15 seconds and
>> when it came back up, there was a 1 KHZ tone for maybe another
>> 15 seconds. CONELRAD receivers had to detect the two drops in
>> carrier plus the tone and that initiated the CONELRAD condition.
>>
>> My father was a science teacher at a school in Tulsa,
>> Oklahoma at the time and had gone in to the teachers' lounge or
>> maybe the school office for something and turned on the radio.
>> He first thought the radio was broken because there were only
>> two signals on the air. Then, he was reminded of the test which
>> went for half an hour or so and then all other stations came
>> back on and things were normal.
>>
>> I think the test was done every year for a while. I
>> don't remember the first test, but the one in 1957 or 1958
>> featured a talk by our state's governor at the time.
>>
>> I bet the station engineers loved this test if their
>> station was one of the CONELRAD stations because they had to run
>> all this stuff that you couldn't test any other time and it had
>> to work perfectly this one day and, of course, be ready to
>> switch in on a moment's notice.
>>
>> Tulsa had a 50,000-watt station KVOO at 1170 which was
>> one of the CONELRAD stations so they had to electrically chop
>> off part of their antenna to tune it up on 1240. I am sure this
>> was accomplished by large contactors which are just huge relays,
>> but still, when else could you make sure it worked?
>>
>> The other 50,000-watt station in Tulsa was KRMG at 740.
>> I have no idea, for sure if they were the 640 CONELRAD station,
>> but they would have had to add some electronic length to their
>> masts to reach 640.
>>
>> It did work, however, so it just shows you what people
>> do when they need to.
>>
>> Something else you might find interesting during those
>> days was a plan to use AM broadcast transmitters as data links
>> for RTTY and Morse.
>>
>> There was an article in "QST" several years ago about
>> WSM 650 in Nashville TN. They actually had a FSK encoder on
>> their 50-KW transmitter which shifted the carrier maybe 50 HZ
>> and would have let them send RTTY to suitable decoders. An
>> average citizen listening to WSM would have noticed nothing
>> unusual. The article described the test transmission as a loop
>> sending the call letters and the word "test."
>>
>> Lloyd Rasmussen writes:
>> > I don't remember hearing any of those celebrity PSA's, but they aren't
>> > very
>> > different from what FEMA tells us today at ready.gov or other websites.