[Hallicrafters] S27 and EBS

[Glen Zook]

That is why most of the old AM broadcast receivers
that were made in the 1950s and into the 1960s have
the little "CD triangle" at 640 KHz and 1240 KHz on
their dials.  This was to tell the owner where to tune
for the Civil Defense information.

I have one of the Heath Conelrad monitors.  They are
fairly scarce these days.

For those stations that were authorized to broadcast
on 640 KHz and 1240 KHz, they used their regular
transmitters and antennas.  There were just some
"special" tuning devices (mostly capacitors) that were
switched in for the Conelrad transmissions.

Frankly, the signal strength of these transmissions
were often "way down" from what they would be when the
transmitter was operating on its "regular" frequency.

Glen, K9STH


--- Roy Morgan <roy.morgan at nist.gov> wrote:

The Conelrad monitors (such as the one Heath made) or
monitor radios, which you may have one of, were set up
with an AVC detector and an alarm circuit, and in the
case of the Heath unit, a relay to de-energize your
transmitter. When the station to which you had tuned
your monitor went off the air, the AVC in the receiver
would go away and light the warning lamp and turn off
your transmitter.


=====
Glen, K9STH

Web sites

http://home.comcast.net/~k9sth
http://home.comcast.net/~zcomco

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