Conalrad

[N8ETQ]

   Good idea? your thoughts please.

/Dan

[wd9ive]

remember reading it was tough on the transmitters of the day

[Steve - K4HX]

Might have been a good question about 50 years ago. 

[KA0HCP]

Conalrad?   

Conelrad, "Control of Electronic Radiation" was a program in the 1950's and early 60's in which broadcast stations would be shut down selectively to deny homing ability to Soviet strategic bombers.  Once ICBM's became operational the program was ended.

Someone else can fill in details about dual frequencies and requirement for ham monitoring.

[Pete, WA2CWA]

And it's Conelrad. Ill conceived notion that AM radio stations were the only things around to provide navigational aid for enemy aircraft. It was killed in the early 60's.

[wd9ive]

oops

[kb3ouk]

That was the exact purpose, make it harder for Soviet bombers to tell where they were at by shutting down all boradcast transmitters, except for a few seleced AM stations which were to transmit on either 640 or 1240, and alternated who used the frequency, so one station would transmit a few minutes than shut down and another station would come on the air. In January 1957, hams were required to monitor a broadcast station and verify every 10 minutes that it was on the air, if it wasn't, then they were to stop transmitting. 

[N8ETQ]

Might have been a good question about 50 years ago. 

   Sorry, the only reason I thought about it
was I was watching an old "Ships Radio Clock"
on Epay. I knew about the silent periods at 15
and 45 after the hour but couldn't recall what
the 4 second red, 1 second black was used for.

   It was to "aid" the operator to activate the
"Auto Alarm". Requred during radio watch on
500kc whenever a ship was at sea with passengers.

   link to old clock

http://www.ebay.com/itm/Maritime-Chelsea-Navy-Radio-Room-Clock-WWII-w-Phenolic-Case-/181249856557?pt=LH_DefaultDomain_0&hash=item2a3355542d

   Link to 500kc radio watch regulations.

http://books.google.com/books?id=7qM8AAAAIAAJ&pg=PA129&lpg=PA129&dq=500kc+radio+watch+regulations&source=bl&ots=DzsO00z74G&sig=b7TG57en1mE-21Udl0kpS5IsfHI&hl=en&sa=X&ei=TmR6UpfrBKa1iwKt2QE&ved=0CCkQ6AEwAA#v=onepage&q=500kc%20radio%20watch%20regulations&f=false


    After a couple more beers, my mind wandered to
other Government Programs that were somewhat less
successful..

/Dan

[W1DAN]

Dan:

My reference for all things Conelrad (spelling is different from subject title) is here:

http://www.conelrad.com/index.php

I even have an atomic war record that has songs from the era. Fun!

I will, tune in to WGU-20 as I get my ham rig ready for the silence periods.....

73,
Dan

[w1vtp]

I was there:  I think "ill conceived" covers it   

[kb3ouk]

The marks on the radio room clock were for hand sending an autoalarm: 4 second dashes with a 1 second space that was transmitted for a minute, then if possible, a 2 minute silent period before the SOS message is transmitted. Conelrad's signalling system involved cutting the carrier for 5 seconds, carrier on for 5 seconds, cutting the carrier again for 5 seconds, then bringing the carrier back up and transmitting a 960 Hz (or 1000 Hz, I've seen both mentioned) tone for 15 seconds.

[N4LTA]

Just glad that we never had to use it!

[Steve - K4HX]

No need to be sorry. We talk about 50-60 year old technology here all the time!

Might have been a good question about 50 years ago. 

   Sorry, the only reason I thought about it
was I was watching an old "Ships Radio Clock"
on Epay.

[KA2DZT]

In the late sixties I worked for Westinghouse.  One of the projects I worked on was a (IIRC) Conelrad radio that was activated by a series of tones.  It worked in the BC band.  The receiver remained silent until activated to receive emergency messages that would have been transmitted.  One model was designed to control relays that I guess would be to sound sirens or other type alarms.  I still have some of the parts that were used in this receiver.

My job was to align, troubleshoot and test to spec the first 100 of these receivers.  My work was done in the lab where they were designed.  BTW, I did have to fix the bulk of all of them.  I also later worked on some of the main order which I think was either a 1000 or 10,000 receivers.

No idea what the government ever did with them, if anything.

Fred

[N0WEK]

http://www.youtube.com/watch?v=4qxGDiDIU4M

http://www.antiqueradios.com/forums/viewtopic.php?f=5&t=207728

http://www.radiomuseum.org/images/radio/heathkit/conelrad_alarm_ca_1_1094797.jpg

[flintstone mop]

I still have this nice RCA radio. Little 1 volt tubes and likes those expensive 90volt batteries. My Dad told me one day," to NEVER play a battery radio in the house".........He cringed when we would go on long trips and I would beg them to buy a battery.....In the 60's that was a big expense around $35.
Very nice audio.
Fred

[flintstone mop]

In the late sixties I worked for Westinghouse.  One of the projects I worked on was a (IIRC) Conelrad radio that was activated by a series of tones.  It worked in the BC band.  The receiver remained silent until activated to receive emergency messages that would have been transmitted.  One model was designed to control relays that I guess would be to sound sirens or other type alarms.  I still have some of the parts that were used in this receiver.

My job was to align, troubleshoot and test to spec the first 100 of these receivers.  My work was done in the lab where they were designed.  BTW, I did have to fix the bulk of all of them.  I also later worked on some of the main order which I think was either a 1000 or 10,000 receivers.

No idea what the government ever did with them, if anything.

Fred

I was a volunteer worker/DJ at a college station and we had to monitor the "EBS" at that time 1977, for the test. It was an AM receiver tuned to one of the stations that was an EBS. Silent until a tone was sent onair. It was then logged in the station's FCC logs for the hourly readings.
The FCC had many visits to WGTB and they were cited for not logging the EBS.
Fred

[n3lrx]

Those EBS tests used to scare the crap out of me. Luckily it only happened about once a month and usually during the day. But they were always unexpected. Luckily it's never happened when I'm actually on the air.

[KA3EKH]

Had an old Gates BC-5 5 Kw AM transmitter on 1470 that had the second crystal for Conelrad and although never tried it would assume that if that was selected cannot see that station making more than a couple watts on that channel. Not just the transmitters tuning but also had a phasor network and base tuning at the towers that would all be way off resonance. Did find the books for the “official” receiver used with that system but never saw the receiver itself. The EBS system that replaced all that junk was a way better system with the two tone generator and the like but the best thing about EBS was the Authenticator list in the red envelope that in the event of the end of the world you would receive a message from the station up stream of you and you were supposed to open the envelope and authenticate that it was a real message by reading the code words that precede the message. If you were the chief operator or CE for the station one of your duties was to replace the envelope every time the FCC sent you a new one every three months or so. EAS that replaced EBS is all automated so the station can run unattended and eliminates all that stuff. I have not seen one of the old EBS folder packages with the instructions and the authenticator envelope for years now.

[KA0HCP]

http://www.americanradiohistory.com/Archive-NAB-Engineering/NAB-6th-Edition/EBS-NAB-engineering-Handbook-6th-Edition.pdf

Excerpt from the NAB Engineering Handbook, explaining the Emergency Broadcast System which superceded CONELRAD.

I remember my elementary school around 1970 having an alerting radio which had a prominent place in the office.

[Todd, KA1KAQ]

Might've been a better system if there were one or two powerhouse stations in the center of the country able to reach both coasts day or night. Instead you had too many stations still on the air broadcasting, when the point was to get stations off the air in the event of an attack.

EBS was replaced by EAS, no idea if that's still current as I've been out of the loop for the better part of a decade, now.

Here are a few related pieces from back in the day. The little Morrow receiver came out of a town office in VT where they were once in all towns. It could tune the entire band but was supposed to be left on the proper 1240 or 640 station for the area. The Kaar CONALERT receiver came from Indiana and has WOWO 1190 in Ft Wayne listed on one of its channels along with several other stations not on 1240 or 640. And of course, the trusty Heathkit CA-1 alarm to keep the hams in compliance. Morrow made an amateur alarm too, as did numerous others. I can't recall the series of carrier/no carrier requirements to trigger them but I'm sure others do.

[W8IXY]

At one of the AM stations I worked at (originally WJW in Cleveland), we had an RCA 10kw transmitter that was set up for dual frequencies.  The Cleveland area was specified to use the CONELRAD frequency of 1240 kc.  The assigned radio station frequency was 850 kc but had switched contactors that could change the crystal and all tuning networks to 1240 with one button push in about two seconds.  The same was true of the antenna system.  There was actually 3 modes of operation on that system, 850 daytime with three towers, 850 nighttime with 4 towers, and 1240 "anytime" with a single tower, and a switched antenna tuning network for each mode.  There were 5 or 6 stations in northeast Ohio that alternated transmitting on 1240 when the CONELRAD system was activated.

I well remember one of the FCC mandated tests back in 1960 that took place an noon Eastern time, and lasted a half hour.  Listening to 1240 (or also as it would have been on 640 in those selected areas) , you heard a jumble of RF, but mostly with the same audio, and as transmitters switched on and off, the reception would vary.

I never did check out why 640 and 1240 were selected for CONELRAD.  I had thought that in the 1950's, there only a few stations in the USA on 640, and the only 640 24 hour signal was from KFI in Los Angeles.  The 1240 frequency was used by several hundred low power. non directional stations, all licensed for 24 hour signals.  Maybe because the phrase "640 or 1240" was easy to remember, or because to the station allotments at the time, those frequencies were used.

Now you got me curious and I am going to search CONELRAD history on the www.


73
Ted W8IXY

[K2PG]

I will, tune in to WGU-20 as I get my ham rig ready for the silence periods.....

The government shut down and dismantled WGU-20 manu years ago. I remember hearing it in the 1980s with a very strong signal, day and night, in New Jersey.

[Jim, W5JO]

Next many of you will tell me you don't remember "duck and cover", especially for kids in schools to dive under their desks.

[Steve - K4HX]

I don't remember it because we never did it. That was gone before I started school.