Conelrad in Boston area

Fri Nov 23 10:41:15 EST 2007

The whole idea was that you could not do direction finding and
especially that enemy aircraft cound not do direction finding! There
was not _A_ 640 transmitter or _A_ 1240 transmitter. The various
participating AM stations in a region (such as greater Boston) were
divided into two groups--a 640 group and a 1240 group. The program
material was fed to all participating stations (I think via a land
line). The several stations in a group would go on the air for a few
seconds apiece in a round-robin sequence. I think that the order of
the round robin and the precise amount of time (number of seconds)
that each station would stay on the air in the sequence varied minute
by minute--controlled by signals sent down the line with the program.
The idea, I gather, was to make each iteration of the round robin
different from the others. Given that the system was set up in the
early '50s, the algorithms that varied the sequences in real time were
probably not very complex because they were likely implemented by some
rather primative mechanical switching technology--a rotating drum,

Anyhow, my understanding is that all participating stations were to
operate ND and that the maximum power of any station during ConElRad
operation was to be 5 kW. There may have been a minimum--I'm guessing
250W--but I don't know that.

If the signals during the test you heard appeared to be coming from a
single source on each frequency, the technology must have improved
considerably from the test I heard in Troy NY in the mid '50s. It was
very obvious when the transmitter switched and because of the smaller
number of stations in the market, there were gaps in the transmissions
(when no station occupied the time slot). The designers of the system
had apparently foreseen this problem (shame on them if they hadn't; it
was pretty damned obvious), so the messages repeated many times--I
imagine, by use of an endless tape loop.

BTW, ConElRad was developed in response to Pearl Harbor; the Japanese
aircraft had used the signals from either KGMB or KGU as directional
beacons. As with so much Civil Defense technology, ConElRad was
designed to fight the last war and not a war that used different
weapons--guided missiles, for example.

Dan Strassberg (
eFax 1-707-215-6367

----- Original Message ----- 
From: <>
To: <>
Sent: Thursday, November 22, 2007 1:15 PM
Subject: Conelrad in Boston area

> When I heard a Conelrad test in 1961 (at age 12), the 640
> transmitter was strong and 1240 was much weaker.
> I was living in Arlington, MA at the time, right next to Menotomy
> Rocks Park and 500 ft. north of Route 2 / Belmont town line.
> The 640 signal was good enough to be from either 590 (Medford) or
> 680 (Burlington): both local-quality then as now of course.
> 1240 may have been from 1260 on the Quincy-Milton line, hardly a
> "barn-burner" signal in Arlington but fine in Boston and nearby
> South and North Shore areas.
> At the time I was under the likely-incorrect illusion that the 640
> and 1240 rigs were at the Framingham (or Natick?) Civil Defense
> facility.
> Since I was so convinced that these transmissions were from
> Framingham-Natick, it didn't occur to me to take any
> direction-finding cuts at the time.  Because I wasn't driving yet, I
> would have had to take a few bus rides to get enough DF lines to
> triangulate these accurately.
> Happy Thanksgiving everybody !
> Mark Connelly, WA1ION - Billerica, MA
> <<
> -----Original Message-----
> From:
> [] On
> Behalf Of
> Kevin Vahey
> Sent: Wednesday, November 21, 2007 9:47 AM
> To: Dan.Strassberg
> Cc:
> Subject: Conelrad in Boston area
> Back in the 50's and early 60's national alerts were to be
> transmitted
> by Conelrad at 640 and 1240 on the dial.
> I recall one afternoon in the early 60's that all Boston ( and
> perhaps
> it was nationwide ) stations signed off for a Conelrad test and
> listeners were asked to go to 640 or 1240 for instructions.
> Where were the Conelrad transmitters liocated for Eastern Mass?
> ________________________________________________________________________
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