[BC] SCA ON TRANSLATORS

[Burt I. Weiner]

I know this is deviating (no pun intended) from the topic, but for 
history's sake... The origin of using subcarriers to "enhance" the 
main channel (FM broadcast audio) goes back to the "Simplex" days 
when super-sonic "Beeper tones"* were used to mute receivers.  This 
was common in the early days of FM Broadcasting when stations used 
their main channel audio for "Store-Casting" or to provide background 
music to restaurants and other businesses**.  As I recall, it was 
sometime back in the late 50's or early 60's when the FCC first 
allowed subcarriers on Broadcast FM to transmit "other program 
material".  Part of the new ruling was to prohibit the use of any 
type of signaling in a subcarrier that could be used to eliminate, or 
"enhance" the main channel programming (content).  In other words, 
you could no longer use super-sonic tones, or control-information in 
a subcarrier to mute or insert content in the main channel.

* 20.4 kHz was a common "beeper signal" to use.  Why 20.4 
kHz?  Because there were a bazillion military surplus 20.4 kHz 
crystal that could be gotten for a few pennies.  I remember during my 
high school days picking up a handful of them for a dime at J.J. 
Glass Electronics Surplus in Los Angeles.

**Would you believe that at one time it was less expensive to put a 
"High-Power"FM station on the air rather than lease phone lines to 
"Pipe" background music into restaurants and the like!  KPWR 105.9, 
originally KBMS,  as well as many other stations in Los Angeles were 
put on the air by background music companies, similar to MUZAK, to 
avoid the cost of program quality phone lines.  KBMS 105.9 was 
originally put on the air by Planned Music Inc. in the mid 1950's.

Burt

>Quoting Tom Taggart <tpt at eurekanet.com>:
> > excludes subcarrier transmissions that enhance main broadcast
> > services--which clearly describes an RDBS transmission.
>
>My take on "enhance" is that "enhance" refers to the coverage area.....
>not supplements to the main signal.......... but I've been wrong once before.
>
>Don R
>