According to http://en.m.wikipedia.org/wiki/CONELRAD the stations on other frequencies than 640 and 1240kHz shut down and the stations that normally broadcast at 640 and 1240 took turns round robin style transmitting.
So nobody switched frequencies or went to lower power.
As someone who has actually navigated a boat by AM band RDF I can say it would be very frustration if the transmitters kept moving around. It would definitely make it harder to find targets in the pre-GPS world.
Too bad about net neutrality. This might really suck.
Steve
On Monday, November 4, 2013, GtwoG PublicOhOne wrote:
Federal circuit court in DC is set to rule on net neutrality and
appears poised to strike it down.
That means say byebye to internet radio. Small-scale community
netcasters won't be able to "negotiate" fees with The Bigs to get
access, even at speeds that are common today in residential
broadband.
If that occurs, it strengthens the moral justification for pirate
radio and similar solutions, by a decimal place or two. In the
spirit of which...
...anyone here ever hear of CONELRAD?
That was the late 1950s - early 1960s plan for Civil Defense
emergency broadcasting in the event of nuclear war. All FM stations
would go off the air, and AM stations would switch over to low-power
broadcast on 640 KHz and 1240 KHz. Incoming Soviet bombers (in the
pre-ICBM era) would be unable to use RDF (radio direction finding)
to navigate, while citizens could pick up the emergency stations
that were nearest to them. Radio dials were marked with little
triangles at 640 and 1240 to make the CONELRAD broadcasts easy to
find.
The signal interference issues Anthony and others brought up, must
have been addressed during the design of the CONELRAD system. If
nothing else, AM reception is more directional, and the lower
frequencies (kilohertz rather than megahertz) would reduce the
problems of signal synchronization, including during times when
official announcements were being broadcast simultaneously over all
the stations in a region.
If this is the case, then blanket coverage by low-power AM
transmitters might be technically feasible.
-G
=====
On 13-11-04-Mon 2:17 PM, Anthony Di
Franco wrote:
There
would be a moire pattern of regions of roughly the
dimensions of a wavelength (~3 meters) within which
interference would be mainly constructive or mainly
destructive. Reception would suck or not exist in all the
regions where interference was not constructive. Then the
usual multi-path interference issues. Complicated and a
good reason to keep transmitters well spaced-out. To do this
right you are pretty much building a phased-array antenna
which uses the interference intentionally to aim the beam by
varying the synchronization among the signals from the
different antennas and that is way too complicated for this
- you have to track the location of the receivers somehow
for one thing, and that's just the beginning.
Also - this is a really dumb question but in terms of
interference, I actually have no idea what sort of
interference results when two coverage-adjacent radios are
broadcasting the exact same signal? Does it make any
difference if they'd both be broadcasting the same signal?
I should remember this, since I actually took one of those
AARL tests wayyy back when (and I think I am technically
FCC licensed, at least for certain spectrums like SSB?
Can't exactly remember..i should have a certificate
somewhere)