[BC] Conelrad

[Gary Peterson]

While cleaning out a transmitter site, I found an
old hardbound book with write-ups of various
broadcast related construction projects.  One of
these was a motor driven shaft with cams that
actuated microswitches.  The purpose was to
sequentially switch audio to various radio
stations that were operating on a CONELRAD
frequency.  The radio stations' carriers were
turned on and off with what hams refer to as VOX.
If the cam-driven audio switcher routed audio to
station A, it would place that station on air.
When audio was routed to station B, station A
dropped its carrier and station B would come up on
frequency.  As I recall, the photo of this unit
showed six or eight cams.  As has been mentioned
earlier, the purpose was to drive radio direction
finders nuts while dispensing emergency
information to the populace.  

Our local 1380 station had a separate, homebuilt,
1240 kilocycle CONELRAD transmitter.  As I recall,
a pair of 810s, modulated by a pair of 810s.  It
was in a wood rack.  I was told that it would
match the impedance of the line going to the
center tower of the three tower array, without any
other changes.  I'm sure the SWR was high but with
a couple hundred watts into 7/8" line, it was no
big deal. 

Gary

"That is a correct statement.   The carrier was
then "voice activated" so 
that when audio
disappeared the carrier went off in a few seconds,
to remain off until 
audio reappeared.
This way, the signal on 640 (and also the signal
on 1240) would appear to be
coming from various locations and so was useless
for navigation.
- JimT"

> I thought the idea was for all stations to stay
on the air but QSY to 640
> or 1240 so that incoming bombers could not use
the signals as navigation
> beacons.
> Rob