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.
http://www.wired.com/opinion/2013/11/so-the-internets-about-to-lose-its-net…
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.
On Mon, Nov 4, 2013 at 2:01 PM, David Keenan <dkeenan44@gmail.com<javascript:_e({},
'cvml', 'dkeenan44(a)gmail.com');>
wrote:
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)
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