RicoGregg said:
Virtually every part of the country has a low power station at 1240 Khz. Most of them are 1000 watts or less. This was originally done in the 40s for Civil Defense purposes. An announcer would tell you after an EBS test "Had this been an actual emergency, you would be instructed to tune your radio to 640 or 1240 for latest news and instructions."
I remember radios with the CD triangles on the dial scale on 640 & 1240. There are only a few stations at 640, most notably KFI in Los Angeles. There are heaven knows how many stations at 1240 all over the place.
In whatever traveling I've done through the U.S., I like looking at all the local radio sites, and I've always noticed that the 1240 sites always seem to have only one tower.
I'm just wondering if any of the 1240 stations in the U.S. are 1) over 1000 watts and 2) directional, with more than one tower?
1230, 1240, 1340, 1400, 1450 and 1490 were established by the NARBA treaty of the early 40's as what were denominated as Class IV frequencies, limited at the time to 250 watts day and night, non-directional. Much later, the maximum power was increased to 1 kw while nights stayed at 250 watts. Finally, they were capped at 1 kw day and night.
Each of the Class IV channels had approximately the same number of stations, although spacing issues and their lower frequencies made 1230 and 1240 a bit more limited. Each of them have around 170 stations, while the higher channels go up to nearly 200.
Right now, there are somewhere around 10 directional stations out of the roughly 1,000 stations on those 6 channels. I believe that each of the very few directional stations was allowed to operate with a DA because of the need to move a transmitter site with the only possible location having spacing issues with other stations.
CONELRAD, the original emergency broadcast system, originated in the late 50's at the peak of the Cold War. The frequencies were selected to be at opposite ends of the dial. The system depended on stations on all frequencies being able to temporarily move to one of the two channels and to operate, each, for very short bits of time. Having all stations on one of only two channels meant that no station or channel could be used by the Soviets to home in on. By having stations in all parts of the country on 640 and 1240 and, within regions, alternating on and off, missiles could not use broadcast radio to home in on.
There were a few tests where every station in the US went off for a half an hour at around noon, EST, and those assigned to local CONELRAD operating zones tested their ability to change frequency and operate with lower power intermittently.
Broadcasting Magazine reported, "The entire U.S. broadcasting structure,
5,070 stations, will go silent 11:30
a.m.-noon (EST) April 17 for the second
Conelrad drill.
Only the 1,200 am radio stations taking
part in Conelrad will operate during
this period. All television and fm stations
will go off the air in the first broadcast
silence since the first major test
July 16, 1956.
The broadcast silence had not been
officially announced until the weekend
though preliminary planning began
several weeks ago (BROADCASTING,
March 16).
Many am stations taking part in the
Conelrad drill—part of a series of civil
defense tests to run during the spring
and summer—will be able to switch to
the Conelrad frequencies (640-1240 kc)
instantly by simply pressing a button.
A half-hour of Conelrad-only operation
will cost the commercial broadcasting
industry upwards of $250,000,
according to unofficial estimates. Few
broadcasters aware of the projected
silence have offered any objections to
the loss of revenue or upsetting of
schedules."
Broadcasting, March 30, 1959
http://www.americanradiohistory.com...page=100&zoom_and=1&zoom_cat[]=2&zoom_cat[]=3
CONELRAD was eliminated after the early 60's and replaced by the EBS, with its characteristic single frequency tone signal and a system whereby stations monitored key EBS stations in their operating area for alerts. The initial system came complete with a coded authentication key that was in a sealed envelope in every station.
But the fact that 1240 had lots of stations had nothing to do with the CONELRAD system.
One station on 1240, WALO, was allowed to run 1 kw day and 5 kw nights under an STA in the 80's and 90's after Venezuela started using 1,000,000 watts on 1240. WALO is in Puerto Rico and did not interfere with other 1240 stations in the rest of the US.
